Weird Water Heater Leak Question

[JOD]

Greetings, and thanks for the awesome forum! I have an odd plumbing question, along with quick backstory:

The water heater is also the supply for radiant heat--so it's running a lot. It's about 15 years old, no problems. It was installed by a general contractor who did the plumbing himself.

Suddenly I noticed some leaking water. The water is leaking from an uncapped elbow coming off of the cold water supply line? In hours of combing the interwebs, I have not seen anything ever plumbed in this manner? There IS an expansion tank, also plumbed in a manner that I've never seen. There is a mixing valve with the hot water supply, and then the expansion tank goes off of that. I'm including a picture--the tank is just out of sight to the left, but you can see how it's plumbed.

First off, I'm wondering how this uncapped elbow wasn't leaking all along? Secondly, I'm wondering what's causing the leak. Other notes:
-the pressure relief valve seems to be working
-the dripping slowed after a let out some water
-the expansion tank is now pressurized at 60psi, was showing 40 (60psi supply to the house)

Note: the smaller diameter tubing in the back from the mixing valve then goes to the expansion tank.

I would ask my friend who did the plumbing what he had in mind with the elbow vent, but sadly he's deceased. Any and all thoughts are welcome!

 

[Reach4]

Leak is at B on the picture I annotated? Mixing valve is at C?

G is the hot water coming up, and D is PVC carrying hot water?

 

[Sponsor]

 

[JOD]

Leak is at B on the picture I annotated? Mixing valve is at C?

G is the hot water coming up, and D is PVC carrying hot water?View attachment 33232

That is correct, leak is coming from B, mixing valve is C.
-Exiting C from the right, that PVC (E) goes to the expansion tank
-G is hot coming from the water heater, D is hot going out to the house

Thanks!

 

[Reach4]

If you turn off your water, and open a faucet to let the pressure out, the pressure tank should become empty (will sound empty when you knock on it). If it is not empty, replace it. If it does not become empty, you still may want to check and adjust the precharge pressure. With a tire pressure gauge, the precharge pressure should be at the water pressure (regulated by the PRV if you have one), or a little above. If it is not, add air.

Somebody may have some further comments on your mixing valve or other aspect.

 

[Smooky]

The "A" looks like a pressure relief valve. "B" looks like someone pluged the presure relief valve. "C" is a swing check. I think you are very confused just like the guy that installed that in the first place.

 

[JOD]

The "A" looks like a pressure relief valve. "B" looks like someone pluged the presure relief valve. "C" is a swing check. I think you are very confused just like the guy that installed that in the first place.

I'm certainly confused--no question there! There is no relief valve of any sort I've ever seen though. It's simply capped at the end with the elbow vent.

It looks to me as though A and B should be removed, and the expansion tank should be installed in that (normal) location. That said, everything was working fine until a couple of weeks ago when the leak started.

I'll try the test on the tank and see what happens.

 

[Smooky]

See if "A" looks like the Pressure Relief Valve in this link:

http://www.homedepot.com/p/3-4-in-Relief-Valve-No-Lead-RV75NL/203449579#.URle7qXLcbw

You could remove it and replace it with a thermal expansion tank as should have been done in the first place.

 

[JOD]

If you turn off your water, and open a faucet to let the pressure out, the pressure tank should become empty (will sound empty when you knock on it). If it is not empty, replace it. If it does not become empty, you still may want to check and adjust the precharge pressure. With a tire pressure gauge, the precharge pressure should be at the water pressure (regulated by the PRV if you have one), or a little above. If it is not, add air.

So, I just tried this test--no change at the expansion tank. So, I'm getting that the pressure is just backing out to the mystery elbow, which is inline before that actual pressure relieve valve. I'll replace the expansion tank and report back. One question question: do I really need to drain the tank completely prior to replacing, or just enough to release pressure?

Thanks all for the help!

 

[JOD]

See if "A" looks like the Pressure Relief Valve in this link:

http://www.homedepot.com/p/3-4-in-Relief-Valve-No-Lead-RV75NL/203449579#.URle7qXLcbw

You could remove it and replace it with a thermal expansion tank as should have been done in the first place.

Great eye! Yes, that's exactly what's there.

So, question:

obviously that's where expansion tanks normally are placed. I can install one there. What about the tank running off from C to E? Should I install that relief valve you posted in that location?

 

[Smooky]

I don't exactly know what all you got there. I would remove the pressure relief valve and throw it away. Then install a new thermal expansion tank in the cold water line before it goes into the hot water heater. It looks like the swing check separates the hot water heater from the water line marked "E" not quite sure why the expansion tank was put up there but I can not see every thing. You may need a licensed plumber to help you sort all that out.

 

[JOD]

I don't exactly know what all you got there. I would remove the pressure relief valve and throw it away. Then install a new thermal expansion tank in the cold water line before it goes into the hot water heater. It looks like the swing check separates the hot water heater from the water line marked "E" not quite sure why the expansion tank was put up there but I can not see every thing. You may need a licensed plumber to help you sort all that out.

Yeah, I was actually thinking that at some point that would probably be necessary. One additional bit of info into the mix, I did see this schematic, which may explain the positioning of the expansion tank: http://www.radiantcompany.com/system/opensystem/

This is the heating system in use, and it's an open system.

 

[Smooky]

That seems strange that cold water supply is mixed in with the hot water cirulating for the heating system. I would think it should be piped to the cold side and go through the heater first. I'm not sure if that is normal or not. There are others that know a lot about this type of heating system. I just don't have much experence with this type heat system.

 

[Reach4]

One question question: do I really need to drain the tank completely prior to replacing, or just enough to release pressure?

Just release the pressure. With the water off, I would a open a lower faucet to let water drain to lower than the connection level of the tank you are removing to minimize dribbling during the change. You could open a higher faucet to admit air, but I think that will not be so important.

While draining is not needed for changing the thermal expansion tank, if you have not flushed the water heater in several years, you might want to consider that. That is a little more complicated than draining the tank, but not much. At a minimum, drain completely. Turn the water back on full as quickly as you can to cause turbulence. Maybe 30 seconds or so. Repeat a few times times.

 

[Smooky]

"A" is a pressure relief valve as discussed above. When cold water heats up it expands and the pressure relief valve lets a little water out each time it expands. They should not be installed in a location that cannot get wet unless piped to a drain etc. They use to be used a lot as an alternative to installing a thermal expansion tank. The price now isn't that much different so I like to use the tanks. There is no water released with a tank. With a pressure relief valve customers often think something is wrong when it is working as it should. There is nothing wrong with having a pressure relief valve if you don’t mind a little water being relieved each time water is heated up and it is in a location where the water leaking out will not matter. They do fail over time and have to be replaced. You could replace it with a new pressure relief valve or a thermal expansion tank. I would not just remove it or plug it up as you have done.

 

[JOD]

"A" is a pressure relief valve as discussed above. When cold water heats up it expands and the pressure relief valve lets a little water out each time it expands. They should not be installed in a location that cannot get wet unless piped to a drain etc. They use to be used a lot as an alternative to installing a thermal expansion tank. The price now isn't that much different so I like to use the tanks. There is no water released with a tank. With a pressure relief valve customers often think something is wrong when it is working as it should. There is nothing wrong with having a pressure relief valve if you don’t mind a little water being relieved each time water is heated up and it is in a location where the water leaking out will not matter. They do fail over time and have to be replaced. You could replace it with a new pressure relief valve or a thermal expansion tank. I would not just remove it or plug it up as you have done.

Gotcha. So, I'll replace that valve with an expansion tank. Here's the thing though: it didn't leak at all (at least any amount that didn't quickly evaporate) for the 15 years of installation. So, I'm wondering if the expansion tank plumbed in after "C" has failed--leading to the pressure relieve valve then leaking. It now almost seemed that A was plumbed as a fail safe in front of the pressure relief valve on the tank?

I do wish I could ask the guy who plumbed it, but alas...not an option...

 

[Reach4]

Gotcha. So, I'll replace that valve with an expansion tank.

You have an expansion tank, but it failed. So while that was good, there was not enough excess pressure to drip water out of B.

 

[Smooky]

That makes sense Reach4. JOD, If you never had any problem before and you know the expansion tank has failed, you may only need to replace that.

 

[JOD]

That makes sense Reach4. JOD, If you never had any problem before and you know the expansion tank has failed, you may only need to replace that.

Makes sense. Thanks Reach4 and Smooky, the help is much appreciated! I'm picking up the expansion tank shortly and I'm going to tackle it tomorrow morning. I'll flush the water heater at that time as well. I need to depressurize the system anyway for an unrelated PEX connection repair, so I'll get it done tomorrow. I'll report back to close the loop. Thanks again guys.

 

[JOD]

OK, so I changed out the expansion tank and the drip went from about 2-3 qts a day to a couple of ounces overnight. So, the overflow tank was the original cause. However, the pressure relieve valve on the cold supply (A) is definitely not functioning correctly, so I'm going to replace that as well (I have a pressure regulator and gauge coming off of the main, and pressure is set to 55PSI, that relieve valve is 75PSI). My guess it that it's just not completely closing the entire way and a tiny bit of water is leaking out of it.

Looking a bit more at how this is plumbed, it does look like this was put in as an extra fail safe if the expansion tank goes south. This may have been recommended by the radiant heat company, as I know the guy who did the plumbing was in contact with them during the install.

Thanks again for the help!