I recently switched to tankless hot h2o heaters. Before the switch the shower in the master bath would put out about 8.5 gpm with the static water pressure set at 65 psi.After the install the same shower is only getting about 7 gpm. When I plumbed the shower I ran 3/4 copper right to each shower head. The reduction to 1/2 was made at the final drop ear fitting. The heaters should put out about 4.5 -5 gpm and there are 3 of them. The units have calibrated and the gas pressure and volume have been checked, so I am trying to figure out why the water volume dropped after installing the rinnais and if it is a water volume issue, how I can fix it. I have also increased the static water pressure to 78 psi with no change. Finally, I took a reading with every hot water fixture in the house turned on (6 sinks, 2 tubs and 4 shower heads on and the max water volume I could get was about 10.5 gpm at 78 psi.
Thanks

Hello Jimbo770, I have few questions:

1. What is your temperature setting on each of these 3 Rinnais ? ( I assume you have 1 control pad for each unit )
2. What model number Rinnais do you have ?
3. How were the 3 heaters connected: in Series or in Paraller ?
4. Did you have Rinnai certified installer doing the installation ?
5. Is the water flow at 7gpm from Cold water side in the shower, too ?
6. Did you clean shower head filter screens and nozzles in that particular shower after installation ?
7. What's the size of incoming gas line feeding these 3 Rinnais ?
8. How far away from the gas meter have these 3 Rinnais been installed ?
9. Are all 3 heaters installed next to each other ?
10. Is this Residential or Commercial installation ? (family house or business type structure )
11. During your Flow Test: Did you turn on Hot water only with maximum reading of 10.5gpm or was it Mixed water reading ?
12. Did you do whole house Cold water Only flow test, too ? If positive, can you post the results of this test ?
13. Did you test the flow at 108 F ? What was the reading ?
14. What kind of water heater did you have before the switch to tankless ?
15. Can you tell us why 3 Rinnais ?

Please, fill me in on these few details so I can better see where your presented problem may be...

Thank you

Milo

120 incoming water temp is 52 degrees

Also the units are 94lsi (3)

1. 120 for each one
2. 94lsi
3. I believe in series. There is a special control unit made by rinnai since there are 3 units
4. Yes. They came highly recommended from rinnai
5. no don't have the exact gpm from the cold side but it is more than from the hot side
6. Yes I did I flushed the pipes for 10 minutes before I installed the showerheads
7. 1.25" with a 2psi meter
8. About 40 feet, but the regulator was moved to the house, about 2 feet from the rinnais.
9.yes
10.residential
11.hot water only. With 1 rinnai I got 5 gpm, with 2, 4.5 each with all 3 I got 3.4 gpm each.
12. I didn't yet but I will. I can only say that it is more.
13. Yes. It was marginally more (about 1 gpm total)
14. 50 gallon gas bradford white power vent unit.
I should add that the rinnais were moved to a new location from where the old hotwater heater was. This increased the pipe run about 20 feet, I thought this could be causing the problem, but a plumber, the rinnai installer, and the techs at rinnai said that shouldn't be causing the problem.


1. What is your temperature setting on each of these 3 Rinnais ? ( I assume you have 1 control pad for each unit )
2. What model number Rinnais do you have ?
3. How were the 3 heaters connected: in Series or in Paraller ?
4. Did you have Rinnai certified installer doing the installation ?
5. Is the water flow at 7gpm from Cold water side in the shower, too ?
6. Did you clean shower head filter screens and nozzles in that particular shower after installation ?
7. What's the size of incoming gas line feeding these 3 Rinnais ?
8. How far away from the gas meter have these 3 Rinnais been installed ?
9. Are all 3 heaters installed next to each other ?
10. Is this Residential or Commercial installation ? (family house or business type structure )
11. During your Flow Test: Did you turn on Hot water only with maximum reading of 10.5gpm or was it Mixed water reading ?
12. Did you do whole house Cold water Only flow test, too ? If positive, can you post the results of this test ?
13. Did you test the flow at 108 F ? What was the reading ?
14. What kind of water heater did you have before the switch to tankless ?

Please, fill me in on these few details so I can better see where your presented problem may be...

Thank you

Milo[/QUOTE]

Based on your response in #11, I am almost sure your problem is your gas supply. You simply don't have enough gas to run all 3 heaters at the same time. Your heater will slow down water flow since it doesn't have enough gas to heat up all the water to the required temperature. I am sure if you turn up your temperature on all 3 heaters to 140F - you will get only trickle from the hot water side in your shower.

Adding one Rinnai to the existing house gas system almost always presents us with problem. Some upgrades are almost always required to assure proper operation of the new heater and not to cut down gas supply for rest of the house. In your situation, you have 3 (three) Rinnais...

It appears to me your installer didn't want to mess with new gas system which is labor intense and could be very costly - so he simply moved gas regulator closer to the heaters figuring he will bring unreduced gas pressure all the way to the gas fixtures - and than he would just ran 24" of gas pipe to supply the heaters itself. Besides, moving pressure regulator away from the gas meter is dangerous as well as it is a gross Code violation - at least in my area.

Also, you will most likely have to have your gas meter upgraded to at least 2" meter or even bigger. I would call your gas company and presented them with new gas demand (measured in Btu's) for the entire property including pool, spa, the 3 Rinnais, BBQ's + every gas fixture in your house. Adding 600,00 Btu's / 550 cfm to your existing house gas system is a major (major) addition that will certainly have negative effect all other gas fixtures in your house.

Please, keep us updated about this issue... Thank you

Cold water flow test for whole house is 18 gpm. After checking my noter the highest whole house water flow through the rinnais at 120 degrees with all fixtures in the house at full hot was 11.8 gpm.
Flow through shower only on full cold is 9.75 gpm. Hot water flow through shower is 7.6 gpm at 120 degrees.

I will check but a permit was pulled the town signed off on the whole setup. I should say my town is over the top when it comes to tankless hot water heaters. They measured the BTU s of all the gas using appliances in the house. They did a gas magnometer test with the techs at rinnai on the phone and everything checked out. They turned on the furnace and stove with the rinnais on full blast and got no drop in water flow. The gas company put in a new meter as well.

Quote:

---

Originally Posted by Milo Dolezal

Based on your response in #11, it appears to me your problem is your gas supply. You simply don't have enough gas to run all 3 heaters at the same time. Your heater will slow down water flow since it doesn't have enough gas to heat up all the water to the required temperature. I am sure if you turn up your temperature on all 3 heaters to 140F - you will get only trickle from the hot water side in your shower.

Adding one Rinnai to the existing house gas system almost always presents us with problem. Some upgrades are almost always required to assure proper operation of the new heater and not to cut down gas supply for rest of the house. In your situation, you have 3 (three) Rinnais.....

It appears to me your installer didn't want to mess with new gas system which is labor intense and could very costly - so he simply moved gas regulator closer to the heaters figuring he will bring unreduced gas pressure all the way to the gas fixtures - and than he would just ran 24" of gas pipe to supply the heaters itself. Besides, moving pressure regulator away from the gas meter is dangerous as well as it is a gross Code violation - at least in my area.

Also, you will most likely have to have your gas meter upgraded to at least 2" meter or even bigger. I would call your gas company and presented them with total number of gas demand (measured in Btu's) for the entire property including pool, spa, the 3 Rinnais, BBQ's + your house. Adding 600,00 Btu's / 550 cfm to your existing house gas system is a major addition that will certainly have negative effect all other gas fixtures in your house.

---

Here is the latest, leading me back to lack of available water flow. With 1 unit on 4.6 gpm. 1 unit turned off 8.3 gpm
2 units on 4.7 gpm each 2 units off 5.2 gpm each. 3 units on 3.5 gpm each 3 units off 3.5 gpm each.

Jimbo: I have additional questions not yet asked:

1. Did replace the shower faucet or are using the old one ? Or Shower head ? What kind/brand/type of faucet is it ?

2. Regarding the latest post #9: these flow rates are measured at the shower head - the point of the flow problem. Is that correct ?

3. Technical Question: You are giving us pretty accurate flow rates information. How do you measure it ? How do you know how much flow each Rinnai produces if they are all tied up to one pipe ?

1. Shower is completely new. All hansgrohe all 3/4". Eco max mixer rated at 20 gpm at 44psi. That goes to 3 seperate volume controls. Rated at 35 gpm at 44psi. Showerheads are as follows 1 - 10" raindance showerhead 2 - kohler forte multifunction shead 3- kohler forte multifunction shead and 1 kohler multifunction hand held shead.

2. for cold water 18gpm for the house was measured at the fixtures. 9.75 gpm measured at the shower heads. For hot water 11.4gpm for whole house is the flow measured by the rinnais. 7.6 gpm for the shower measured both at the showerheads and through the rinnais. Allreadings at the fixtures were measured with a bucket that I marked at .5 gal increments.

3. I turn off the water to each rinnai one at a time and get the flow through each unit(they all have independent shutoffs)

Quote:

---

Originally Posted by Milo Dolezal

Jimbo: I have additional questions not yet asked:

1. Did replace the shower faucet or are using the old one ? or Shower head ? What kind/brand/type of faucet is it ?

2. Regarding the latest post #9: these flow rates are measured at the shower head - the point of the flow problem. Is that correct ?

3. Technical Question: You are giving us pretty accurate flow rates information. How do you measure it ? How do you know how much flow each Rinnai produces if they are all tied up to one pipe ?

---

Jimbo...

This HansGrohe Eco Mix shower faucet has service stops. Please, check the hot water side to see if it is open all the way... Also, you may have some debris lodged inside hot water channel slowing down the flow...

Also, check if your temperature valve is properly calibrated...

If you set temperature on Rinnai, to - let's say to 96F - does the water flow on Hot water side / inside your shower - improve ?

Sorry, regarding post 9... these measurements were taken at the rinnais. With the units turned off then on (power) the with the units turned off and on (water)

i.e. with the units powered off and all the hot water fixtures in the house turned on I got 8.3 gpm through 1 unit, with water running through 2 units and power still off I got 5.2 gpm each for 10.4 gpm total, and with water running through all 3 units power off I got 3.5 gpm each for a total of 10.5gpm.

With units turned on and all hot water in the house turned on I got 4.6gpm through 1 unit with the water to the other 2 units turned off, With 2 units on I got 4.7 gpm on each of the 2 units and with all 3 units turned on I got 3.5 gpm each for a total of 10.5 gpm.

According to the manual I should be able to hold 3.6 gpm at up to a 90 degree rise, but when the guy was working on the unit yesterday he did something to the unit so now I can't get it to go above 120 degrees. I wanted to see if I raised the temp to 140, if I could get more flow at the fixtures because Id have to mix in more cold water.

Do you have single control pad ? Or 3 ?

Stops are open all the way. I have the 100 degree stop calibrated at plus 5 degrees(we like a warmer shower) I didn't calibrate the high temp side so it will put out 140 degree water. I haven't flushed the system since the rinnais were installed so maybe there is some debris in there. I will flush the mixer and recheck the flows at the fixtures and at the heaters.

This HansGrohe Eco Mix shower faucet has service stops. Please, check the hot water side to see if it is open all the way... Also, you may have some debris lodged inside hot water channel slowing down the flow...

Also, check if your temperature valve is properly calibrated...

If you set temperature on Rinnai, to - let's say to 96F - does the water flow on Hot water side / inside your shower - improve ?[/QUOTE]

Each unit has its own control pad but only the master unit control pad will adjust the rinnais i.e. changing the temp on the master unit will change the temp on all 3 units

Quote:

---

Originally Posted by Milo Dolezal

Do you have single control pad ? or 3 ?

---

Yes, that is correct. I see that you did your homework and that you are familiar with the system... I would unplug it and plug it in again. It will reset itself to 96F. Than, you will have to set temperature again...

I would also try to call HansGrohe, technical support to see what can inhibit water flow in the Eco valve...

Have you tried to phone Rinnai engineer ? (... not the local distributor or Rinnai's area Rep... they don't know anything, they just care about sales... ).

Jimbo: Do you have hot water circulation pump installed ?

No circ pump. I have talked to the engineers at rinnai, I will try the hansgrohe engineers as well. I am in the process of flushing out the mixer and will report back when it is done.

There was a little debris in the mixer. Cleaning it out got me to 8 gpm from 7.6 gpm measured at the rinnais. Still 1.75 gpm less than full cold through the shower. I am out of ideas.

That's a good news. Now we know that "...little debris..." will take away about .5 gallon of water from overall water flow. Maybe, we should look some more... Did you check hot water stop valve if it is fully open ? Check the ThermoValve cartridge, too.

I talked with Rinnai people few minutes ago at 800-621-9419 / dealer- installer line (... I am also Rinnai certified installer). I explained your situation. They feel it is not w/h problem. They said if you call them they will be glad to discuss your problem with you. Unfortunately, they asked me questions about your house that I could not answer. In any case, they said they will welcome your phone call. Please, call them and let us know what they suggested. Milo

Let me also ask this... if water volume is the problem how can I increase my water volume to the house. The watermain is 3/4' copper. The waterpressure regulator is set to 78 psi so I really can't increase the pressure anymore. I know the incoming city waterpressure is pretty high, I can't recall the exact number but I think it was in the neighborhood of 125-150 psi. Could I go from 3/4 to 1 inch upstream of the pressure regulator and then run 1 inch all the way to the rinnais before switching back to 3/4" since the city water pressure is so high? Or would I need to run 1" from the water meter?

He hot water stop is full open. I will call hansgrohe tomorrow to get their take. I have spoken with rinnai a few times and the have changed their story a few times. Latest is the pressure loss through the rinnais. They say there is just not enough water flow through the units. I find that hard to believe since rinnai has some engineers here in CO at the Stanley hotel where they have 11 units plumbed together, so if that were the case how could they get enough water flowing through 11 units? Im sure they have a much larger main but Im also sure they have much longer plumbing runs to the fixtures etc.

Quote:

---

Originally Posted by Milo Dolezal

That's a good news. Now we know that "...little debris..." will take away about .5 gallon of water from overall water flow. Maybe, we should look some more....Did you check hot water stop valve if it is fully open ? Check the ThermoValve cartridge, too.

I talked with Rinnai people few minutes ago at 800-621-9419 / dealer- installer line (.... I am also Rinnai certified installer). I explained your situation. They feel it is not w/h problem. They said if you call them they will be glad to discuss your problem with you. Unfortunately, they asked me questions about your house that I could not answer. In any case, they said they will welcome your phone call. Please, call them and let us know what they suggested. Milo

---

Jimbo: how big is your house ? How many bathrooms ? How far is your house from the curb ?

Water volume can be increased by increasing pressure. But increasing pressure creates its own problems. Average house plumbing system is designed to operate under 40-50psi of pressure. All pipes are sized accordingly.

House is 2000 sq ft. 2.5 bathrooms. I just started finishing the basement which will add another 1000 sq ft and 1 more bath with multiple showerheads. That was the reason for the 3rd rinnai. The water pressure had been set to 65 psi. I just raised it to 78 to see if I would get any appreciable increase in flow. There was some but not a tremendous amount. That is why I was wondering about going to 1" pipe for the main. The huse is very close to the curb... about 10-12 feet, and the watermain enters the house about 30 feet from the water meter.

Quote:

---

Originally Posted by Milo Dolezal

Jimbo: how big is your house ? How many bathrooms ? How far is your house from the curb ?

Water volume can be increased by increasing pressure. But increasing pressure creates its own problems. Average house plumbing system is designed to operate under 40-50psi of pressure. All pipes are sized accordingly.

---

Jimbo, that water main is definitely undersized. You should have at least 1" water main and continue with 1' pipe all the way to feed the first 2 bathrooms, Rinnais and washer. Then you can reduce to 3/4". You can call your Building Dept./ Plumbing engineer and he'll tell you right away what size pipe you need.

( Presently, we are working on very similar house. It is 3,096sq feet, 4 baths, 2 Rinnais. Rinnais are not together: One is direclty behind Master Bathroom and serves only Master Bath. The other one is on the other side of the house supplying rest of the house with hot water. Blueprints asked us to run 1 1/4" cold water line starting at the meter, unreduced, through entire house reaching every bathroom and both Rinnais. Hot water is 1" main run with 3/4" branches to each shower valve. Master Shower has 5 shower heads. Pressure here is 115 psi reduced to 55 psi. ).

Can you run 1" directly to the rinnai or do you have to reduce to 3/4 before entering the units? Unfortunately, running 1" to the master is not going to be possible without ripping open some walls, which Id like to avoid.

Quote:

---

Originally Posted by Milo Dolezal

Jimbo, that water main is definitely undersized. You should have at least 1" water main and continue with 1' pipe all the way to feed the first 2 bathrooms, Rinnais and washer. Then you can reduce to 3/4". You can call your Building Dept./ Plumbing engineer and he'll tell you right away what size pipe you need.

( Presently, we are working on very similar house. It is 3,096sq feet, 4 baths, 2 Rinnais. Rinnais are not together: One is direclty behind Master Bathroom and serves only Master Bath. The other one is on the other side of the house supplying rest of the house with hot water. Blueprints asked us to run 1 1/4" cold water line starting at the meter, unreduced, through entire house reaching every bathroom and both Rinnais. Hot water is 1" main run with 3/4" branches to each shower valve. Master Shower has 5 shower heads. Pressure here is 115 psi reduced to 55 psi. ).

---

You would run 1" to the Rinnais and connect each of them directly from the 1" pipe.

Spoke to the city, currently have a 5/8" tap with 3/4" main. To increase to a 1" tap would be $46000, so that is not going to happen. I am trying to get the actual city water pressure, but I am still wondering if instead of going from a 5/8" tap to a 3/4" main, going to a 5/8" tap to a 1" main would do anything since the city water pressure needs to be reduced through the water pressure regulator?

City pressure at the street is 136 psi. Setup is actually a 3/4" line to a 5/8" meter to a 3/4" main. City is telling me to crank up water pressure even higher, which doesn't sound right to me. However just wondering for a test, how high I can raise the water pressure to see if I can get any more flow through the rinnais?

Yes, City fees are high no matter where you are. However, you don't have to have the meter upgraded. Just upgrade water main. I would install 5/8" -to-1" increasing bushing right on the water meter and continue with 1" line towards the house.

You can increase pressure as high as you want. I don't know what kind of pressure regulator you have. Typical residential pressure regulator, like Wilkins 70 and Wilkins 600 go up to 75psi maximum. I would suggest that you use Braukmann pressure regulator that will allow you to turn up your pressure up to 300psi. Also, Cash Acme makes such a regulator. I don't think you can get those in Home Depot, but you can get it in pro-plumbing supply house, like Ferguson Enterprises, or Hirsh Pipe and Supply. I think Hirsh will ship out. You can Google them, both companies are well know suppliers.

Increasing pressure will present you with new set of problems. One of them is noise caused by friction. You may be hearing water as it travels through pipes. Depending on how is your house plumbed, it may be too audible. Also, your pipes may knock and bang caused by changes in pressure as you open and close valves. That is especially true with washing machine (solenoid valve) and toilets. You may also notice that some fixtures are not operating properly ( or harder ) due to increased pressure on closing mechanism.

But give it a try. See if you can achieve the desired water flow... Let us know how you did...

As a test I turned off toilets and ice maker so nothing would explode, and turned up water pressure to 130psi. Flows through the rinnais were 4.6 gpm through 1 rinnai turned on 7.8 gpm turned off. 4.4 gpm each through 2 units turned on 4.4 gpm each turned off and 3.0 gpm each through 3 turned on and 3gpm turned off.

Just curious to avoid major excavation, what if I stayed with the 5/8" meter to 3/4" main for 30" until it entered the house, and then switched to 1" pipe with a 1" pressure regulator downstream of the switch from 3/4 to 1". How much of a difference would the 30 feet of 3/4" copper make?



[QUOTE=Milo Dolezal;1672389]Yes, City fees are high no matter where you are. However, you don't have to have the meter upgraded. Just upgrade water main. I would install 5/8" -to-1" increasing bushing right on the water meter and continue with 1" line towards the house.

You may be running out of water supply to your 1" pipe. In other words, it won't be refilling your plumbing system as fast as it should. It will show decreased water delivery (volume).

Rinnai says that the supply has to be reduced to 3/4" before entering the unit. Are you saying I should run 1" to the rinnai, reduce to 3/4" into the rinnais and then 3/4" out of the rinnais and then increase back to 1" for the run to the mixing valve and then switch back to 3/4"?



[QUOTE=Milo Dolezal;1672185]Jimbo, that water main is definitely undersized. You should have at least 1" water main and continue with 1' pipe all the way to feed the first 2 bathrooms, Rinnais and washer. Then you can reduce to 3/4". You can call your Building Dept./ Plumbing engineer and he'll tell you right away what size pipe you need.

So this would be the case if I kept the 3/4" copper? Do you think I would have no problems at all if I made the switch right at the meter from 5/8 to 1"?

Quote:

---

Originally Posted by Milo Dolezal

You may be running out of water supply to your 1" pipe. In other words, it won't be refilling your plumbing system as fast as it should. It will show decreased water delivery (volume).

---

Run 1" all the way. Do not reduce. Feed all 3 Rinnais out of 1" pipe. Cap 1" at the end. See pic...

Quote:

---

Originally Posted by jimbo770

So this would be the case if I kept the 3/4" copper? Do you think I would have no problems at all if I made the switch right at the meter from 5/8 to 1"?

---

Yes, you would have no problem if you switch to 1" right at the meter.

Jimbo: I have a meeting in 20 minutes. I will have to run for now. I will log in later in the afternoon... Thank you. Milo

What about coming out of the Rinnais?

Quote:

---

Originally Posted by Milo Dolezal

Run 1" all the way. Do not reduce. Feed all 3 Rinnais out of 1" pipe. Cap 1" at the end. See pic...

---

As for hot water side, proceed the same way: 3/4" risers going into 3/4" main run.

In this example, is the 1" hot main you mention downstream of the rinnais? If so are you coming out of the rinnais with 3/4" and then going back to 1". Also what kind of flow are you getting through the master shower with all 5 heads turned on? Finally, how big is the water meter?

Is there a way to determine how much my flow will increase if I run a 1" main from the meter to the rinnais, and 3/4" hot to the master shower? I am open to replacing the main, but since it will probably be a gigantic nightmare, I'd like to have some idea how much the benefit will be.

( Presently, we are working on very similar house. It is 3,096sq feet, 4 baths, 2 Rinnais. Rinnais are not together: One is direclty behind Master Bathroom and serves only Master Bath. The other one is on the other side of the house supplying rest of the house with hot water. Blueprints asked us to run 1 1/4" cold water line starting at the meter, unreduced, through entire house reaching every bathroom and both Rinnais. Hot water is 1" main run with 3/4" branches to each shower valve. Master Shower has 5 shower heads. Pressure here is 115 psi reduced to 55 psi. ).[/QUOTE]

Also, I am planning on adding a recirc pump with a small 5-6 gallon electric hot water heater, and probably the grundfos comfort system pump, using the cold water line as a return. Will this negatively affect my flow rate? Just wondering since you and the engineers at rinnai asked if one was installed?

Installing circulation pump with a small elec. Storage tank should not have effect on water flow - as long as you don't connect it before shower connections. It has to be connected on the return, preferably close to Rinnais. Also, make sure you purchase proper pump, like LAING or Gronfo made specifically for tankless heaters. Ordinary pump will not do the job.

Milo,

Sorry I double posted so I don't know if you saw this post.

Thanks,
Jim

In this example, is the 1" hot main you mention downstream of the rinnais? If so are you coming out of the rinnais with 3/4" and then going back to 1". Also what kind of flow are you getting through the master shower with all 5 heads turned on? Finally, how big is the water meter?

Is there a way to determine how much my flow will increase if I run a 1" main from the meter to the rinnais, and 3/4" hot to the master shower? I am open to replacing the main, but since it will probably be a gigantic nightmare, I'd like to have some idea how much the benefit will be.

( Presently, we are working on very similar house. It is 3,096sq feet, 4 baths, 2 Rinnais. Rinnais are not together: One is direclty behind Master Bathroom and serves only Master Bath. The other one is on the other side of the house supplying rest of the house with hot water. Blueprints asked us to run 1 1/4" cold water line starting at the meter, unreduced, through entire house reaching every bathroom and both Rinnais. Hot water is 1" main run with 3/4" branches to each shower valve. Master Shower has 5 shower heads. Pressure here is 115 psi reduced to 55 psi. ).[/quote]

Jimbo: excuse the timeliness of my response to your last post...

I am enclosing sketch of our ongoing project to better illustrate my explanation. The project is scheduled for trim installation for 1st week in June.

I do not have some of the details you are asking. Usually, HomeOwner hires her own architect who in turn has her own engineer to work out the details of the project. All we get is a spec mechanical page in a set of blueprints that gives us all final dimensions. Detailed calculations, like Flow, or methods used to arrive on proposed pipe sizes are not included...

In the case of our ongoing project, we have 1 1/2" meter split into two 1 1/4" water mains. One is going to Sub-Meter ( I do not show this in the sketch) and the other continues to the house. House is a large, single story, ranch type house and is about 97 feet long. There are 2 Rinnais: one on one end of the house supplying hot water for whole house - except master bathroom. Main line continues unreduced across entire length of the house and terminate on the other end with connecting the second Rinnai. Connections to the Rinnais from the main are done by 3/4" risers directly from the 1 1/4" main. Risers on both Rinnais are about 24" long.

Each Rinnai delivers hot water from 3/4" x 24" piece of pipe into 1" main hot water run which in turn continues to each plumbing fixture. ( 1/2" branches for sinks and tubs, 3/4" for showers. In case of Master Bath, the second Rinnai is only 8" away from the first shower valve ( on the same wall, shower valve is directly behind Rinnai ). Master Bath has 5 heads. All are Grohe, including 16" jumbo rain shower head. All heads are rated at 2.2 gln/m flow. (11 gpm demand / total ). I will test it after the trim is installed. As of now, I cannot expand on the gallons per minute flow since I do not have this info at this time...

You may place phone call to City Mechanical Engineer with the flow question. (S)he should be able to give you this info in a minute. You will need to supply the following info:
1. Total Developed length of pipe
2. Pressure at the meter
3. Pipe (material) used + its size
4. How many 90's, 45's etc. You have to estimate here...

If my memory serves me well, you use "Hazen-Williams" method or "Manning" Formula to figure it out. Then, you have to adjust for friction loss and pressure loss to get Flow Rate (gpm) and/or Velocity (ft/s). But not sure here. It has been "few" years and I am not a mechanical engineer... :D

In my area I cannot remember the last time we used 3/4" as main water supply for residential house. 1" is minimum and widely used, 1 1/4" is not that uncommon when used, and 1 1/2" is used on oversized houses. Sizing is important. Correct size of pipe not only delivers required volume of water across the house but also cuts down on friction noise during delivery.

Today, and w/o giving full story, I asked few installers their opinion to your problem. I wanted to see their first response. Most of them said "inadequate gas supply". ( Rinnais produce less hot water when they don't have enough gas supply ), as well as they questioned the 3/4" pipe...

Rereading your previous post that includes the test numbers, I do not understand the following: If you - lets say - run 2 Rinnais / hot water only / you should max out the water flow at your Eco valve. Instead, you are getting only 2 x 4.4 glns. That bugs me. Rinnai engineer told me that with 2 - 94LSi Rinnais running simultaneously you should be getting 18.8 gallons, a volume your Eco valve can handle. Here is where I suspect inadequate pipe size...

Time to call your engineer. I am sure (s)he'll know in a second what is inhibiting your water flow...

Please, come back to let us know what you've found out..

Regards / Milo

OK here's the latest. The city I live in will not allow me to increase the water main size to 1" without increasing the meter. They only allow an increase of 1/8" from meter to main.

Speaking with Hansgrohe today, I found out that the ecomax rated at 20 gallons, needs close to that volume to operate properly. Also the hot and cold pressure have to be close(I forget the exact psi he mentioned) or the mixer will also start acting screwy. I can swap out the ecomax with the ecostat which is rated at 13.2 gpm which will help the flow issue, but we are still getting a pretty big pressure loss through the rinnais. So here's my question, could I T off the cold water main upstream of the pressure regulator, and run either 3/4 or 1" pex directly to the rinnais? This would shorten the run, remove 6 or 7 elbows and I am hoping deal with some of the pressure loss through the rinnais since we would have 120+/_ psi going into the rinnais. Also since it would be on the hot water side, the icemaker, toilets etc would not be affected by the higher water pressure.

On another note. The water pressure regulator is a conbraco. It says max inlet pressure is 400 psi with an operating range of 25-75psi, however if I crank it down all the way I can get static pressure of 120+psi. Why is that? Finally, With static pressure set at 80 psi I am getting a pretty big pressure loss with the rinnais turned on. Each unit will run at 4.5 gpm. Starting at 80 psi static, if I turn on 1 rinnai pressure drops to 65 psi, 2 units on 60psi 3 units on 55psi. I am wondering why there is such a large pressure drop since the street pressure is 136 psi. Do you think one of the other regulators you mentioned would maintain a more constant pressure as the units are turned on?

Jimbo: before I respond to your latest post: can you post a photo of your 3 Rinnais installed ?

I will be meeting with Rinnai rep on the 30th. I will print out our conversation and present it to him. Hopefully, he will be able to come up with solution...

You should not read pressure higher than 75psi behind regulator. Otherwise, your regulator is not working properly - or is installed backwards.

It is always good idea to run pipe as directly run as possible. Every elbow will present you with pressure loss - and lower pressure will effect volume delivery to your fauct. Same with long length of pipe. You will be losing pressure with long runs. Pressure loss in these cases is not significant but some loss is there. If you want to run new dedicated Pex line, don't use 3/4". Go with 1".


Jimbo: what area are you in ?

Milo,

I am in Colorado. I will post some oictures this evening. The regulator is installed properly (arrow is pointing the right way) I have a call into conbraco to see what they say.

Here's some more info that I have gathered. If I run the Rinnais with hoses hooked up to the drain valves (taking everything downstream of the rinnais out of the equation) I get the rated flows on all 3 units (approx 4.5-5.3 gpm depending on rise) If I turn on all the 2 handled faucets in the house on (no mixing valves, and there are 5 sinks) I get 7.5 gpm which is exactly what they are rated for. If I put a demand on the Rinnais greater than 10.5 gpm (going through the actual plumbing in the house, the rinnais will max out at 10.5 gpm which I can't for the life of me figure out.

I did the hazen williams equation and got cold side - 9.08 ft/sec - 9.5 psi/ft h2o - 4.1 psi head loss through 100 ft of pipe to the aster shower. Hot side - 9.08 ft/sec - 15.7 psi/ft h2o - 6.8 psi head loss through 160 feet of pipe, but I have no idea what these numbers tell me.

I have ordered an ecostat mixer which may help, but I won't get that for a week or so.

Regarding a separate run to the rinnais. Do you think it would be OK to run a 1" pex line directly to the rinnais using unregulated water (upstream of the regulator) and if so and I install a recirc system using the cold water side for the return, will there be a problem since the hot water side would be unregulated and the cold side would.

The Instantaneous Gas water heaters have a flow control valve that modulates to reduce the flow rate through the water heater in order to maintain the required outlet temperature. This is one of the drawbacks of instantaneous water heaters. If the flows change the outlet temperatures change. To counter this newer models have controls to modulate the outlet HW flow to help maintain the temperature. In the winter time the incoming cold water temperatures drop especially in northern climates. In order for the instantaneous water heater to maintain the hot water outlet temperature it has to slow the flow of water down to allow enough heat to be added to raise the cold water temperature from 40 degrees up to the desired temperature.
I find it much easier and cheaper to just purchase a 50 gallon storage type water heater for less than one-third the cost of one instantaneous heater (about one tenth the cost of three instantaneous gas heaters) Then there will be plenty of hot water and no hassles.

Ron George

Quote:

---

Originally Posted by Plumbing Expert

The Instantaneous Gas water heaters have a flow control valve that modulates to reduce the flow rate through the water heater in order to maintain the required outlet temperature. This is one of the drawbacks of instantaneous water heaters. If the flows change the outlet temperatures change. To counter this newer models have controls to modulate the outlet HW flow to help maintain the temperature. In the winter time the incoming cold water temperatures drop especially in northern climates. In order for the instantaneous water heater to maintain the hot water outlet temperature it has to slow the flow of water down to allow enough heat to be added to raise the cold water temperature from 40 degrees up to the desired temperature.
I find it much easier and cheaper to just purchase a 50 gallon storage type water heater for less than one-third the cost of one instantaneous heater (about one tenth the cost of three instantaneous gas heaters) Then there will be plenty of hot water and no hassles.

Ron George

---

The problem is, even with reduced flow the shower uses about 8 gpm, so a 50 gallon storage tank doesn't provide enough water. I looked into larger hot water heaters but the unit being replaced was a 50 gallon power vent model, a 75 gallon unit was $3500 for the unit alone, definitely not 1/10th the cost of the rinnais and it would still run out of hot water pretty quick .Also if you read my previous post, the rinnais will put out their respective rated flows when I open the drain valves and run the water directly out that way. It is only when I run through the plumbing that I start getting flow loss.

I am going to swap out the regulator on Mon. The local plumbing distributor said the conbraco is limiting the flow considerably and with a different unit (he recommended the watts 223) which is a super capacity unit should increase flow as well as maintain a more constant pressure as demand is added. I will let you know how it works out.

Here are the pics

Jimbo: thank you for posting the photos. With your permission, I will print them out and show them to the Rep. I will let you know what he had to say.

Btw: Nice and clean job... Keep the plumber ! :D