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Water heater pressure relief valve leaking. Advice needed

10 years ago

Recently purchased a condo that has a gas water heater with power vent. I discovered a rubber hose connected to the pressure relief valve downspout and there has been water leaking from the valve.

What is the probable cause of this and what is required to fix this? I have never seen this happen in any other water heater.

Thanks,
Dave

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Comments (8)

User
10 years ago
The valve you are talking about is a pressure relief valve (PRV). It is a safety device to prevent WH explosions.

Either the valve is bad and needs to be replaced with EXACTLY the same spec valve despite what a vest wearing know it all at a box store says... "this one fits everything".

Or you have a closed plumbing system and you have a thermal expansion problem that needs to be corrected NOW.

If you have a closed plumbing system, and that has been code since the 90's, there should be a small thermal expansion tank installed proximate to the WH. These tanks have a bladder that may have failed and the tank must be replaced.

OR... you have a closed plumbing system and there is no thermal expansion device installed, which is not uncommon, and there needs to be one installed. In this case the PRV is acting as a thermal expansion device and it is NOT intended to.

Here's some light reading on thermal expansion... http://www.watts.com/pages/learnabout/thermalExpansion.asp

If this seems beyond your skill level call a plumber... and do it SOON.
User
10 years ago
Very common for sediment to get under the valve and cause leakage. Lifting the valve manually can cause the seat to clear, however it is also possible to scald oneself or have a major blowdown if the valve does not shut.

Some people manually lift the relief annually to prevent this very thing.

The thermal relief is required whether or not you have an expansion tank.
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The relief valve is made by others not Bradford White. I think the heaters now come with the valve installed. Ck to see if it is leaking from the relief tube or the threads. Either way this is a safety device & should be checked. If the heater is 1 year old or less your plumber can get some labor from Bradford White. Did you buy the heater or did the plumber. If you purchased it thinking to save money. You didnt. Most plumbing contractors will warranty their work for a year.
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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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While these are Âpressure relief valves,Â the acronym for that is PRV, which is reserved for Pressure Regulator Valve. So, the popular term for the one you mention is, T&P. That means Temperature and Pressure, and that is really not just more descriptive, but more about your question: "Are (these) valves likely to cause problems?" They are there to solve problems, but interestingly enough, they are a bit of a nuisance. The two conditions are both capable of opening the valve. But the valve is kept closed by a spring. It so happens, that Â especially with older installations Â once a valve is opened and allowed to close naturally, it is more likely to leak. The reason for that, is that the valve is installed in the new condition, with all forces at rest. But if the Temperature and/or the Pressure increase to the danger point, the valve is expected to open. This suggests that moderate over-heat or moderate over-pressure will partially change the spring position or its stored energy. Then, a small influence can open it. This is usually apparent in the appearance of a minor leak. It is the nature of a seat-type valve to have a ÂhomeÂ position. That is, once built, the rubber washer settles on the metal seat, forming a fit natural to the variety of parts and their tolerances. Disturbing this fit changes the nature of the valve, which tends to stay changed as long as the heater is under heat and line pressure. Conversely, if you were to shut OFF the water, remove, clean, chill and reinstall the valve, it should be in Âas newÂ condition and then operate that way. Of course, it could do that without all this. But when they become leakers after opening, it is for a good reason. The ordinary and reliable solution Â especially for professional service people Â is to replace the valve with new. This avoids call-backs and is less labor-intensive ($$.) Your other concern, "My wife is convinced it'll rust out in no time and we'll need a new one." Baloney. Women are just fickle that way. For instance, if she uses a Lawyers-page from the local telephone directory to bookmark her romance novels, you can be sure sheÂs like that. DonÂt worry, once it dries up sheÂll be very comfortable with it Â the water heater, that is. Pinoke
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Thanks. I am assuming given that I am not going to be using the air conditioner for 6 more months, I can drain it out and should be good? Wrong, during heating condensate is also produced. It needs to be fixed before both the cooling and heating season. I also suspect the condensate pump considering it is full, it will normally empty out once the float activates the pump but clearly there is something wrong with yours. The pump may have just quit working and need replaced. They are not that expensive.
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daven
Original Author
10 years ago
The heater is off so I will try lifting the valve tomorrow.
User
10 years ago
PRV valves are not designed for intermittent use. Whether the cause of the leak is dirt or excess pressure is irrelevant. For sediment to get under the valve (in the valve seat, the valve had to be opening and that is indicative of a bad valve or excess pressure in the plumbing system. The valve should be replaced and the cause of the valve failure identified and repaired.

Thermal expansion is one of the most ignored and misunderstood plumbing conditions by both homeowner and handyman(woman) types. Thermal expansion problems are common and easy to resolve.
User
10 years ago
Er, ah, OK... as I said, "Some people manually lift the relief annually to prevent this very thing." Note the words 'annually' and 'prevent.'

Additional, by design of this valve and its significant "blowdown" it is not dripping a few drops to prevent an overpressure situation due to a solid system.

This post was edited by saltidawg on Sat, Apr 19, 14 at 20:13
jakethewonderdog
10 years ago
Hey Dave,

As mentioned before, the expansion tank (or lack thereof) may be the source of your problem, as Lurker has mentioned. You will want to resolve that problem if you have it.

In any case, replace the valve. It's just not worth dinking with it.

But something that wasn't said - the hose on the outlet pipe really isn't kosher.

The pipe coming from the PRV must not be reduced in size from the outlet of the PRV (or have any kind of valve on it). It should terminate near a drain and it must be visible if there is a water discharge.
homebound
10 years ago
I just had a customer who's newly installed hot water heater began to leak after 3 months. (Turned out the Installer kept the existing expansion tank when he installed the new tank.). PRV was dripping about 1/2 gallon/day. New expansion remedied it. (Work done by a pro.)
User
10 years ago
daven,

what was the final determination?

SaltiDawg

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