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:

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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.

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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:

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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 ?

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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:

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Originally Posted by Milo Dolezal

Do you have single control pad ? or 3 ?

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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:

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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

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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:

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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.

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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. ).