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Heating & Air Conditioning

HW Heater Pressure Relief Valve Leaking

8 years ago

We just had a sprinkler system installed yesterday and I just noticed that the HW heater pressure relief valve is dripping hot water occasionally.

I had the boiler tech just come out and he said that I need to have an expansion tank installed on the HW heater and that he's certain that's the issue. He was unable to do it on the spot and suggested I find out why the sprinkler guys didn't do it.

Does that make sense?

Also, we are leaving on vacation tomorrow morning. I turned off the boiler and shut off the water to the boiler. But, I still want to run the sprinklers because we have a newly seeded lawn that will need water.

Will I be safe for the week that way? It's going to be 45-70 degrees out while we are gone.

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Comments (7)

PRO
Austin Air Companie
8 years ago
what is this a boiler as in boiler for heating the home? OR a hot water heater for heating water used for bathing and such?

These are not one in the same.

The sprinkler system should be tied into cold water supply before water shut off and is controlled via valves that are controlled typically by a low voltage controller. The sprinkler system is or should be a separate system that uses incoming cold water, not hot.

A pressure relief valve for a water heater's main purpose is to relieve pressure. If it is leaking occasionally it is doing it's job. If it leaks continuously you may need to replace the valve because sediment can get into the closing part of the valve and prevent it from closing properly.
mike_home
8 years ago
What probably happened is the sprinkler guy installed a back flow valve in the water supply going to the sprinkler and the hot water heater. It should only be installed on the feed to the sprinkler system. When the water is heated, it expands but the water can't expand past the back flow valve. If the back flow valve can't me move, then the fix is to add an expansion tank near the hot water heater.

The leaking pressure relief valve is a sign the pressure is building up. The relief valve should never leak in my opinion. It is there as a safety valve. You need to get this addressed soon otherwise you will be replacing the hot water heater some time in the near future.
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SORRRY (havoc) for the mis-use of terminology! I was told (by manufaturer) to close it back a hair to restrict the pressure since it was going to 30#plus. Thats when It was over flowing. Since I have adjusted it a bit it seems to drain allot less water. none the less still a quart or so per week. (Coolvt) it is getting up to 30#s at full heat 170. Which valve are you suggesting is leaking the Pressure relief valve is bad or the Pressure Reducing Valve?
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hi..your not going to like me..... I read your post and started chuckleing to myself back in the early to mid eighties..the tandom water heater hook up was the "deal" ..and then in the early 90's or late 80's..we started switching back the heaters..your not getting more than 45 --55 gallions of hot water.. do you know how the piping is piped in your house we used to go in the attic..cut the pipes loose and blow thru them [open allvalves] figure what pipe goes where split the house up..between the 2 heaters..master bath ,laundry on one heater and a bath and k-sink on the other
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Isn't the PRV spring loaded? Once the pressure is released, it should close and seal. In this case, when I flipped the test valve, the "plunger" pulled out but was not pulled back in. I think the spring is shot. I doubt its actualy due to high pressure, more likley the PRV has failed on its own. The only other thing could be the supply side pressure reducer failed and is allowing to much pressure into the system. Unfortunatley, there is no pressure gauge on the system to check. I may place a pressure gauge over a boiler drain and open the drain just to check the pressure is OK. I can isolate the boiler from the zones so repair is not an issue for me. Just a threaded 3/4 connection, so thats easy.
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Dave, Sounds like you may be confused between a PRV (pressure reducing valve or pressure regulating valve) installed at the water service entrance and the T&P (temp & pressure) relief valve installed on the WH. A PRV is installed at the service entrance to lower the street pressure to an acceptable PSI for the houses plumbing. Depending on water conditions they go bad and need to be replaced from time to time. They are usually set to around 60 psi. A T&P relief valve on the WH is a safety device and is installed so the water heater doesn't explode if pressure problems arise. When these T&P valves leak they MUST be replaced and with EXACTLY the same specification part or maybe... BOOM. The expansion tank should be check annually when you drain your water heater. You do drain your WH annually don't you?. To do that you put an air gauge on the air valve. If the bladder has failed then you'll get water out of the air valve. If you don't get water then you must drain all the water from the tank, which usually requires removal, and the air bladder needs to be pressurized to what the water pressure is when the tank is empty.
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PRO
Austin Air Companie
8 years ago
The back flow valve in my area is installed outdoors, areas that get colder in the winter I don't know where they would put this.

The pressure relief valve is there to relieve pressure, it can not relieve pressure without leaking some water in my opinion. With that said, most of the time they do not leak and sometimes if you catch it leaking you can manually open it to clear debris from it and if it's OK it should reset itself and stop leaking fairly quickly.

I'm not a licensed plumber so do not call me for plumbing problems, but back in my early years of maintenance I was forced to work on this stuff.
klem1
8 years ago
What Mike said is true,t&p probably started leaking after sprinkler co installed a back flow device. There are other possible explaninations but that is the most likly. You'll be fine until comeing back from vacation.
David
Original Author
7 years ago
No problem while I was away.

Came back and turned on boiler again and later that evening had a funny
mothball type smell in house. Called FD and they detected some low
levels of CO and thought that the burner was putting out some CO when
that kicked in. Does turning the boiler off for a week have anything to
do with that?

Boiler tech installed the expansion tank. Confident that will remedy
the problem with the overflow water dripping out. Now he's giving the
boiler/burner a thorough cleaning.

He also tested the water pressure and said we are at around 85-87 or so
and we should look into a plumber installing a pressure reducing valve.
Is that something that would be recommended?
klem1
7 years ago
Definatly need whole house regulator if city run's 80 plus. Most tanks develop odors if water stand's in them more than a few days. It's caused when heat destroy's the chemicals in water alowing crud to grow in tank. Worse on some supplies than others but it can be pretty rank.
mike_home
7 years ago
With pressure that high it is understandable why the hot water pressure release valve is leaking. I would recommend no higher than 70 psi, and 60 psi should be adequate. Reducing the pressure will save on water bills and not put so much stress on the plumbing.

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