Hi, I'm going to describe this problem with as much detail as possible. Any help would be appreciated.

We have a 28 room motel. Basically, we have to run the cold water for a few minutes and wait for the hot water to stop coming through. Eventually, cold water starts coming.

We have 2 large water heaters which are running in series and both are pretty old. The cold supply goes into the bottom of the water heaters, and hot comes out of the top. The cold water from the city splits and goes into the first water heater and also feeds the rest of the building. The city cold water pipe which goes towards the rooms gets very hot (just as hot as the "out" side from both water heaters). We are thinking that the water is backfeeding from the first water into the cold side.

Today, we turned off the supply to both water heaters (even though they are in series). We opened the "hot" side in several rooms and the flow of water never stopped (was hot at first and eventually become cold, but not ice cold like the cold side).

We have single lever sinks faucets and showers. We tried to close the supply to as many sinks as possible, but the "hot" side always kept flowing in the rooms we were using to test. We didn't test 8 sinks. For the tubs, it is a lot more difficult to shut off supply since they are tub/shower combos with no access to shut the water off to them.

What could be the problem? Is it a cross connection issue? Is it a backflow issue from the water heater into the cold lines?

If its cross connection, how can we easily isolate this at such a large property? How would a 100 room hotel go about doing something like this? I can't imagine they would test each shower and sink one-by-one.

Thanks in advance.

IT is a backflow through the single handle valves, but we cannot tell you which ones or how many. Do you have Mixet tub/shower valves, because that is a know problem with them. IF not, then you probably have Moen faucets which can also cause the problem but not as often as the Mixets.

HJ, do you mean a cross connection?

How can we determine which one easily (whether sink or shower) ? The showers also have single handle valves, but we don't have access to shut supply just to one shower.

Why is the cold water pipe going into the first water heater getting so hot so quickly when the water is not in use? Its hotter towards the water heater at first, then gradually gets hotter further away from the water heater.

Not really a "cross connection" because the valves ALWAYS have a hot/cold connection, but the mechanism keeps them separated. What is the make and model of the shower valves, or give us a picture so we have a better idea of what you are working with. NOT ALL single handle valves can mix the hot and cold piping.

The heat radiates through the cold water inlet and some water backs out of the tank when it gets heated. BUT, that is NOT your problem since the hot water keeps flowing with cold water when the heater is shut off. Once we know what kind of valves you have we should be able to give you a diagnosis.



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you probably have to round and round feeling the cold water pipes going to the showers.
the problem is that if it is a backflow issue, it could be one or many of the showers???
so, get out your sherlock holmes hat and start feeling the cold pipes to each shower. none of them, i repeat, none of them should be hot..

So a failed mechanism on one or more single handle faucet can create a cross connection?

I can post pictures, but we have many variations of faucets for the sinks which have been changed by different owners/managers over the years.

For the shower, we have all Moen faucets, but we have replaced a lot of cartridges with off the shelve generic brand cartridges from home depot. Previous managers/owners probably did similar repairs.

Packy,

We have tub/shower combos with the single handle faucets. Is there enough room to feel the cold water pipe in these setups? We don't have access panels behind the showers.

You have bad Moen cartridges, but it is almost impossible to tell WHICH ones are bad. You may have to replace all of them and possibly any Moen sink faucets as well, because it is probably several of them that have gone bad.

The pipes he has to feel are inside the walls and he would have to remove the trim rings to feel them. The problem is that when he repairs the ones that have "high" flow, he will have to do it again because some of the ones that were okay to start with will probably now demosnstrate a crossover pattern.

given that you have no access to the pipes behind each tub, it might be better and cheaper in the long run to invest in a 18V oscillating tool and 28 inexpensive plastic access panels and cut them in.

Try using a cheap IR thermometer. Remove the escucheon, in say, room #1. Take a reading on the hot and cold side of the valve body. Running the water in room #2, should not make those readings change. This technique has been used in hotels to find bad cartridges.

Thanks, Packy. Our rooms are back to back (14 rooms in the front and 14 in back) since we have exterior corridors. That's how things were done back then to save money.

Plumbing runs in the center of the building between rooms so can't make panels even though I would love to. One tub/shower backs up to another on the other side.

Thinking I will have to to use HJ's and Paul's recommendations to isolate the bad cartridge.

Changing all of them will be a very costly endeavor.



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Folks,

I'm reading somewhere that I can shut off the supply to the hot water heaters, and also turn off the circulation pump.

Then, i need to turn on all my faucets to the hot side. When I turn on the bad one to the hot side, all others should turn off since the crossover will break when the bad one is turned on and in the hot position. Seems like a good (and cheap) approach.

Thoughts?

No one has asked if the recirculation line has a dedicated return line. If not, then the cold water line acts as the hot water return. That's the drawback to that type of hot water circulation system.

The hot water return line is dedicated. There are two lines joining at the inflow side of the recirculation pump since the water heaters are in the middle of the building.

Does the problem appear at the very end of the line? If the last unit at the end of the hot water distribution/ beginning of the return line has cold water to start, then check for the crossover in the next unit toward the tanks. Wherever the hot in the cold line starts is probably the culprit, but as hj said, it may be multiple connections causing the problem.

The problem is that ONE valve would not cause your problem. You have several, or many, and that complicates the process of finding them.

The "retro" circulations system would NOT be used in a motel. They have a dedicated return line and pump.