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mkejp · Dec 9, 2009, 05:01 PM

I live in a 9 floor, 30 unit residential condo building and we have historically experienced intermittent problems with hot water getting to units or taking a long time to warm up. Recently the problems have gotten much worse and we are seeing complete outages on mid to high level floors. We have 2 gas water heaters (I believe installed in 2002)with one pump. The temp on the water heaters reads approx. 150 degrees so it seems as though that aspect might be o.k. We have been told that the pump is working fine. Units on the lower levels will receive hot water after running the water for 5 minutes or more but above approximately floor 4 no hot water is available to units. The current suggestion is that this could be an individual unit, fixture problem and that all units will need to be evaluated on a one-off basis. The contention is that a faulty valve may be causing a cross connection. Admittedly I have zero plumbing expertise but I have trouble thinking a single unit fixture could cause the entire system to malfunction. It would be an extremely timely and expensive undertaking to be checking unit by unit for each hook-up. My questions are does the above description fit the current diagnosis and are there any other troubleshooting methods that could be tested prior to the individual unit inspections? Hopefully that all makes sense... happy to provide clarification and thanks in advance for any suggestions.

ballengerb1 · Dec 9, 2009, 05:04 PM

Is there a property management company associated with this building? Individual owners or rents should normally not attempt repairs or alterations on what is considered common property.

Milo Dolezal · Dec 9, 2009, 09:51 PM

First: was there any plumbing work done at any of the condos in the building recently ? Or, is there any unit under remodeling now ?

Every time water is closed in the building the circulating system has to be bled. Otherwise, pumps won't function properly...

mkejp · Dec 10, 2009, 10:23 AM

We are working with the property management company; decisions are not made at an individual unit level regarding repair work.

No plumbing work done recently and the no units in the building are under remodeling.

ballengerb1 · Dec 10, 2009, 10:38 AM

The fix, whatever it will be, must be done by a licensed plumber so call 3 for their read on the situation and costs. Nothing can beat an onsite inspection which we can not do.

KISS · Dec 10, 2009, 10:43 AM

This is probably a recirculating loop that runs all the time. This the pump not being able to pump the required head makes the most sense.

If there are check valves in the system, these would be suspect too.

The flow rate needs to be checked even if it means cutting into the line to do so.

mkejp · Dec 11, 2009, 07:58 AM

I guess what is most odd and making it more difficult to figure out is the fact that the system seems to self correct. Starting yesterday the water was back to hot for all units. We have had a professional out but even they are struggling to understand why the problem seems to come and go every six to nine months. Of course now that the system is working again it is difficult to do any additional troubleshooting.

KISS · Dec 11, 2009, 02:06 PM

Do you have an automatic air bleeder on the system or an expansion tank?

cyberheater · Dec 11, 2009, 03:31 PM

When you have that fixed, correct your temperature on the hot water heaters, turning them up too high can cause someone to get scalded. Turning the water heaters up too high is not an answer to a problem either.

You say this happens every 6 -9 months. Your water heaters in this setting are usually flushed about this time, is it after doing this that this is happening? You do need a license professional, but I know it would be nice to try and figure out the problem.

speedball1 · Dec 12, 2009, 09:49 AM

The temp on the water heaters reads approx. 150 degrees so it seems as though that aspect might be o.k.

It wouldn't be OK for the person standing under a 150 degree shower.
The settings are way high. A common mistake is thinking the higher the temperature the more hot water.
The factory setting's 120F. I advise setting it back to 110F.
I don't recommend a 150 degree setting for two reasons.
1) It's a waste and a costly one because you have to temper it down with cold water, **and**
2) you could get scalded with a bad burn.
Check the recirculating system and reset the temperature. Regards, Tom

mkejp · Dec 15, 2009, 08:25 AM

We have an expansion tank.

I do not believe the problem occurs after the water heaters are flushed. Although I will need to check when the last time they were flushed. Could lack of regular flushing be causing the problem?

Point taken on the 150 degree setting and we will adjust. Can you be more specific on what "check the recirculating system" means? Is this simply checking the pump or are there other aspects to the recirculating system that could be causing the problem?

KISS · Dec 15, 2009, 09:04 AM

I disagree with Tom, that a higher temperature does not give you a longer shower. I do agree with Tom that the temperature should be lowered.

It should be lowered by resetting or using a mixing valve and not the boiler. I think it's resonable to assume that say 0.75 times the number of units. Assuming they are all taking a shower at the same time to go to work in the morning, thus the temperature, mixing valve temperature, # of people showering at the same time and hot water storage are all inter-related and determine "How long can I take a shower for?"

Recirculating system checked:

1. Particulates in the shower can ruin things for the pump. At the very least strainers should be installed and designed such that they can be changed without impacting use. (Bypass valves).

2. Pumps have seals. Pumps are generally designed to be able to raise water a certain height, If the seals are bad, the pump is broken and cannot get the water high enough.

3. I can't remember by fluid mechanics well enough, but I think that if you had all the taps open on the first floor, it would be more difficult to get the water up three floors. Water takes the path of least resistance.

4. Water pressure should be checked on all floors.

5. The only real way to "check" the recirculatig system is to check the flow rate. If a flow meter is not installed, probably it should be.

6. Dp tubes. If there are any storage tanks at all, make sure the dip tubes are not deteriorated, New hot water should be introduced at the bottom of the tank.

7. Automatic air valves can/should be installed to reove air from the system.

8. I would imagine that some check valves are installed in the system although they don't have to be if the system is continuously re-circulating.

9. If you can imagine how a system like this could work.
1. You need a method to heat the water
2. You need a tank to store the water
3. You nned to introduce hot water in the storage tank at the bottom
4. You need an expansion tank
5. You probably need at least one check valve at the cold water supply and then the expansion tank.
6. Two Hot water lines are run: One is the hot and the other is the return.
7. For instant hot water, the system runs all the time.
8. For energy savings, the pump may run depending on temperatures. For even greater energy savings, the setpoint of the boiler can depend on outside temperature.
9. There may be two pumps that alternate for reliability reasons.

speedball1 · Dec 15, 2009, 12:31 PM

I disagree with Tom, that a higher temperature does not give you a longer shower.

And I disagree with that. Raising the temperature in your water heater won't increase the volume that comes out of the shower head. You can temper it down with cold water but when you're out you're out. There's a reason that the factory setting on water heaters are set at 120F. That's so people don't get scalded when they first turn the shower on. 150 F. is just too damm hot.
Want longer showers? Increase the capacity of the water heater. Tom

KISS · Dec 15, 2009, 01:49 PM

Nope, won't do anything to increase the volume of water (GPM), but 40 gallons of 150 deg water mixed with 55 deg water will last longer mixed at 120 deg, than 40 gallons of 110 deg water mixed with 55 deg water for the same discharge temperature. This assumes the same flow rate and discharge temperature.

The shower head limits the discharge flow and the hot water temperature limits the maximum temperature.

Assuming the shower mixing valve regulates the outgoing temp which mine does and any ADA valve should, showers will last longer.

The hot water storage tank essentially supplies a water supply whose temperature constantly decreases over time.

First hand, hotter water temps; longer showers and risk of getting burnt.

It may also depend on the thermostaic mixing valve that's use. There is a flow-temperature-valve position relationship

cyberheater · Dec 16, 2009, 08:48 AM

KISS, this is happening two times a year.

KISS · Dec 16, 2009, 10:22 AM

OK, if you want to assume that, then the hot water system isn' an isolated entity.

Say that so much cold water is used for some event, and the hot is taken faster than the cold can make up. You get AIR.

With no auto-air valves, you have stuck hot water.

Event examples:

Filling of the cooling towers
Fire hydrant testing

Pressure of the hot water should track the pressure of the cold. Make expansion tank bigger.

speedball1 · Dec 16, 2009, 12:33 PM

KISS,
You're making a major assumption that everybody has a thermostatic control on their shower valves. They don't. In my area none of the hundreds of condos we have built have thermostatic shower controls.
While it may b e true that you can stretch out your shower by tempering 150 degree water with cold it comes at a price.
1) Every time you temper hot water with cold it costs you money. First the cost of heating the water and second the cost to cool it.
2) With 150 degree water you stand a real chance of getting scalded with a regular shower valve.
In my home I've set my temperature for as hot as it's comfortable for me, (about 110 or 115F)so I don't have to spend money cooling it down.
Let me repeat, "as a rule 150F is just too damm hot!!"
Now let's look at from your side. In a high raise, even with a recirculating system the water will cool before it reaches the top floor unless they have a "booster heater" installed in a mid level mechanical room along with a booster pmp to maintain pressure. Is that the situation you're describing? Best regards Tom

KISS · Dec 16, 2009, 02:17 PM

150 F is too hot. Back to the problem

I dug this out about hot water piping design in high rises: Central Hot Water in High-Rise Buildings - Cover Story - PM Engineer

Note the mention of getting rid of the air at the top floor.
That makes a lot of sense.

Thanks Tom. I think it makes sense too.

It looks like th eprimary reason is air entrapment and the air comes from the water as the water is heated. A malfunctioning air release vale at the top of the hot water riser would be the first place to look. Air rises, so it makes sense that the upper floors would be affected. Air is compressable, water is not.

From the paper, it seemed that there should be check valves and flow meters at the horizontals with valves to balance the system.

Probably all that information has been lost.

You could guess that as you go further up, the balancing valves would be more open.

Th horizontals wouldn't count much unless a check valve is stuck open. Not sure exactly how one might detect that. Attempt to create a reverse flow condition with a pump and a pressure gauge? Inject air? If you can pump from say a laundry outlet without raising the pressure, then you have a broken check valve.

Using a stupid approach. Fill a janitor tub with cold water. Put a sump pump in it. Put pressure gauge and check valve on the outlet. Turn off all water and try to pump into system.

Just ideas. I really don't think it's related to a unit, but depending on how the system is engineered it might require sporatic outages for tennents to isolate.

I'd start with the automatic air valve.

There may have been a possibility that the air valve was located at the water heater and it was removed when replaced. Did I remember that? If it's generated at the heater, someone may have decided to put it there.

mkejp · Dec 18, 2009, 08:48 AM

Thanks for the article and other troubleshooting tips; we have requested the building plumbing plans and now I think we have several areas to explore.

Feedback from all has been much appreciated... happy holidays.

KISS · Dec 18, 2009, 12:14 PM

Let us know what you find and even how things are laid out.

An observation section Plast-O-Matic Valves, Inc. - Plastic sight glasses, double wall sight glasses, level indicators would be nice to install in the riser before the air release valve. It would also give a "proof positive" that it's working. Remember, that you can't use PVC for hot water.

Once you know the layout, you may have to have a PE re-engineer the flows, so the system can be balanced again.

There are programs that make the job a lot easier. About 18 years ago when my fluid mechanics was fresh in my mind, I could probably do it. Now, forget it. I had to write Fortran programs to do the analysis. A real pain.

My hunch at this point is when the heaters were replaced in 2002, the air eliminaters were inadvertently removed. The best place is the top of the highest riser, but having one installed at the boiler too would not be a bad idea.

Find the hot water riser and check for an Air Vent valve. See if you can arrange for the installation of an air vent valve if it's missing, and/or the installation of an observation section of pipe.

A building is an "engineered machine" which needs periodic maintenance and inspections. HVAC, security, water, sprinkers and fire alarms are part of those inspection.

Happy Holidays!