Water in bottom of heater tank - and - hot water in cold lines

[SteveRiley]

I am unsure of whether my symptoms reveal two problems or if they're related. Anyway...

Friday morning, my wife complained of no hot water for the shower. When I went to investigate the water heater, I noticed a small puddle surrounding it, a circle approximately two inches wider than the base of the heater. I peeked into the pilot light viewport and saw that the light was out. I re-ignited it, waited a minute, then switched on the burner. The burner lit, and then extinguished, along with the pilot light.

Thinking I had a leak of some kind, I called the company that installed the system in January 2008. The plumber removed the door at the base of the heater and noticed standing water. He vaccuumed out about one third of a gallon, he estimated. He waited a bit and noticed no leaks. He lit the burner and let it run for a while. Again, no leaks. We discussed the situation, and he concluded that the problem is condensation, because the heater is sitting directly on a concrete floor and can't get enough air for combustion. He said to keep an eye on it, and if the problem returns, they'll come install a stand to raise the heater to improve airflow. This would not be covered by the heater's warranty, of course, and I'd have to "pay a little bit."

On Saturday I noticed some water around the heater again. And on Sunday, my wife's shower ran out of hot water. I opened the door on the heater and -- sure enough -- the problem had returned.

I have spent a few hours reading through various posts on several forums and have concluded that the condensation diagnosis is wrong. The volume of water just seems too great, and why would I just now have a condensation problem?

Possibly related (or not), for a few weeks now, I've noticed that very hot water will come out of our faucets when the cold side is opened. This happens if no water water has been flowing through the house plumbing system for a few hours. I mention this second symptom because I don't know if the two are related.


Here is a diagram of my hot water system:

The expansion tank, installed at the same as the water heater:

The check valve; this is the original valve that came with the house, built in early 2002:

And the tank itself. Note that the T&P valve is piped outside:

When I looked outside, there was no water where the pipe exits the house.


Now for my questions.

Why is hot water entering the cold water pipes? Isn't the check valve supposed to prevent that backflow? I'm wondering whether the valve is damaged. The valve is now 10 years old. When I tap the side of the expansion tank, it rings hollow for the upper 75% of its height. Water does not spurt out of the Schrader valve. The pressure at the valve is 65 psi. I have not depressurized the system to check the tank's pressure in that state. I suspect the tank is OK.

Where could the water in the bottom of the tank be coming from? Do T&P valves leak inside the space between the heater's jacket and internal tank?

I am somewhat reluctant to call this plumbing company again until I have a better understanding of possible causes. Thank you for reading this post, I know it's long, but I wanted to ensure I covered all the details.

 

[journeyman]

i doubt that it is because of condensation. If you are getting water inside burner and around outside of tank it is more than likley the tank. t&p valves can leak around threads and run down insde of jacket. also the tank could be leaking from the back where you can not see. i think the check valve is could be bad. If you are getting warm water than the cold is draining backwards in check valve. also depending on the local codes if your heater sits in a garage or closet where flamable materials are stored it might need to be on a water heater stand to prevent fires and explosions. It looks like there is calcium build up around top of t&p valve which indicates a prior leak. You get calcium growth from a leak. check top of heater to make sure it is dry also check to make sure drain bib is not dripping. also if i am right why do u even have a check valve after expansion tank and before heater. and expansion tank is used for thermal expansion of the heater if there is a check valve then the expansion tank is use less. no water is going to be able to enter expansion tank through check valve. remember heat rises so the hot water is at the top of the tank

 

[journeyman]

on the picture you drew is that the check calve on cold line before heater

 

[stevemachine]

And to add to journeyman's thread, if you have the expansion tank there and it's useless, the check valve makes the system closed and therefore no where for the hot water to go. It puts extra pressure on the tank and may have caused premature failure. If the expansion tank was in the right spot then a check valve is totally fine. Also the expansion and having no where for the hot water to go could have caused the check valve to fail.

 

[IFIXH20]

You could have a hair line crack which leaks when the water heater heats up. Take & post more photos of the water heater and piping standing back to get a complete picture of heater & piping . The water heater & pipe drawing show a check valve on the cold side ,if the system is pipe that way ,you have a close system. Take more photos for proper diagnosis.

 

[johnjh2o]

There should not be a check valve between the heater and the thermo expansion tank.
It may be that your getting condensation because of poor combustion do to a plugged filter on the bottom of the heater. Some of the manufactures had a problem with this. Call the heater manufacture for instructions on how to clean the filter.

John

 

[journeyman]

the expansion tank should be after the check valve. I think you have a crack in tank and that is what is causing the water under heater. And who ever you used as a plumber should have been aware of the check valve and where it should go.

 

[PioneerPlumber]

Is there a recirculating system? That's the only reason I can think of for a check valve on the cold inlet. Expansion tank should be after the ball valve, check valve and in the cold side. This way the heater is protected even if the ball valve is **** off.
Also, I would install a pressure gauge onto the drain bib and mark the needle while pressure is relieved. See What the pressure increases to while heating. I've seen pressure build up and blow the T&p within 5 min... You may have an intermittent leak directly associated with the pressure and temperature of the tank.

Also, I've seen condensation lines connected to flue pipes on the roof before... Just sayin.

As stated before, please take some photos of the entire installation!

 

[Beni]

As others have said the expansion tank goes after the check valve. If you had water at the air valve the bladder would have failed.

I'm assuming you don't have a high efficient condensing water heater, but a regular water heater and a metal flue.

My guess if it was fine before but now there's water inside and outside the heater, its a pinhole failure in a weld seam that breaks open when hot and pressurized and once the heater cools down the seam closes and water does not leak, Not much anyway.

It's NOT condensation. The seam would have failed as the water in the tank had no where to go, the T&P relief did not pop, and the expansion tank was on the wrong side of the check valve.

The hot water on the cold side was caused by the high pressure in the tank pushing water past the check valve seat into the lower pressure cold water line. Hot water rises and I'm betting your H&C water lines are in the ceiling.. It did not fill the expansion tank as the cold side and tank were at the same pressure..

Was the very hot water on the cold side steaming hot??? If so the thermostat could have gone bad

Lucky you, the seam failed. The T&P should have popped before a seam let go. Did the water heater installer also install the expansion tank???. If so and the water heater is under warranty, have it replaced and the expansion tank located to after the check valve. The seam failure was caused by the expansion tank being before the check valve.

Really if you don't have a recirc system with a pump by the water heater, the check valve can be left out.

Beni Bacon, PE, CIPE

 

[SteveRiley]

Wanted to follow-up. The installation company decided to do a full warranty replacement. New tank and no charge for equipment or labor. They agreed that the earlier suggestion of condensation was incorrect.

Both the old heater and the new one are regular water heaters with metal flues, but direct vent.

The system is in a small room in the back of the garage, on the first floor of the house. The first floor also has one bedroom with a sink/toilet/shower. All the rest of the house is on floors two and three, which is where the majority of the plumbing exists -- so yes, nearly all hot and cold lines are above the heater.

I simplified my earlier diagram to try to keep the post from getting too long or complicated. Because this curious check valve has aroused suspicion here and on another forum, it seems important to provide more detail. Here's a complete diagram:

The water heater heats the house by sending hot water to six fan coil radiators. Cold water enters the system and hits a tee (1). One output goes to a mixing valve, the other output passes through the curious check valve and into the water heater. Hot water exits the heater and hits a tee (2). One output goes to the mixing valve, the other output goes to the fan coils (via an electric circulator). Water from the fan coils re-enters the water heater via a tee (3) in the cold line after the curious check valve. Since this system requires a higher water temperature, the mixing valve combines some cold water with the hot water to reduce the temperature of the water that goes to faucets.

The question mark points to the curious check valve. I can see why this valve would impede expanding water from getting to the tank. Perhaps this valve is installed to ensure that return water from the fan coils flows only into the water heater and not back into the cold water supply? This is the original design -- including the placement of the expansion tank and the curious check valve -- as configured by the builder of my house in 2002, not something done during the tank replacement in 2008.

Also: I close the ball valves near tees 1 and 3 until winter sets in because water rises through the piping into the fan coils even when the circulator isn't running. The house has many south and east facing windows and it simply gets too hot if I don't shut off the water. Recall the second problem: hot water coming out of faucets in the cold position -- hot water is forcing its way through, as you say. To experiment, I opened the ball valves before the replacement tank was installed and plugged in the circulator. Hot water flowed through the fan coils as usual. Interestingly, hot water no longer appeared when the faucets were opened to cold. It's as if the additional piping for the fan coils provided sufficient additional expansion space.

I had never really researched how this system works before, and have learned a lot about closed heating systems and what expansion tanks are for. It would seem that the system has a design flaw -- I suspect I need to move the expansion tank to a place in the cold water line after the check valve. I'll probably replace the valve at the same time I relocate the expansion tank -- that valve has been under stress for many years, it's likely not to be in very good shape now

 

[Beni]

Yes the check valve on the cold water is to prevent the pumped hot water from going into the cold water line.

Where there is a check valve on the cold water to the water heater, such as in your case. The expansion tank always goes after the check valve on the cold water side.

 

[PioneerPlumber]

I'd love to see the actual photos of the installation. Just sayin

 

[journeyman]

it will be easier for us to fix problem to see photos instead of a drawing

 

[SteveRiley]

Sorry for the late reply. I was away on business travel.

Additional photos below.

 

[Beni]

Ah, so the expansion tank being on the wrong side of the check valve was part of the original installation. The installer should have noted that and made the fix when they put the new water heater in. But took the easy way out.

The trick is the check valve is in the right location in relationship to the tempering valve and manifold. So the expansion tank needs to be moved and connected to the cold water piping after the manifold connection with a tee in the short section of copper labeled cold... You'll going to want to anchor the tank to the wall too as the short piece of copper will not be ridged enough to support the expansion tank.