Periodic release from (I think) the T&P valve on the water heater

alexz

Hello all,

About once every 4 to 6 weeks, I notice water in the basement coming from the hot water heater. I'm never present when it happens, I just find water running from the heater to my drain. I do not see any noticable leaks and since this is not a constant problem, I cannot think of where else it could be coming from but the T&P value. The first time it happened, I had taken a long shower after working in the yard. But there seems to be no rhyme or reason to what's causing these other incidents. I use the shower and sinks daily and the clothes washer about twice a week.


What could the cause be? The manual to my hot water heater says: "If the T-P valve weeps or discharges periodically, this may be due to thermal expansion. Your water heater may have a check value installed in the line or a water meter with a check valve. Consult your local sears service center for further info."


I see no type of valve in the line leading to the heater. I tried looking at the water meter, but it's mostly covered in soil. The water supply line coming into this 56 year old house looks fairly new. It also mentions that the T-V value should be operated manually each year. It's been 8 months since I've lived in this house and I haven't done so yet. Would this help to solve the problem?

There's more in the manual for the heater, in bolded letters. "The temperature pressure relief valve is not intended for constant relief of thermal expansion. This is an unacceptable condition and must be corrected."

However, the following website reads: "The relief valve relieves this pressure by discharging sufficient water to bring the pressure down to acceptable levels. If you don't want a pressure relief valve to release this water, you would need to install a thermal expansion tank in the water line to absorb the expansion." (From http://www.keidel.com/mech/heaters.htm) This website makes it sound like a choice or a preference. The water from the heater doesn't bother me - I can live with periodic draining of water from the heater to the basement's drain. All of the items I store in the basement are nowhere near the heater and are off of the ground anyway. To me, it's no big deal if it's not a safety concern. And installing one of these thermal expansion tanks seems like it would be expensive since most of the supply plumbing in this house is galvanized iron.


The 'handbook' that the home inspector gave me notes that "TPR valves sometime discharge a little bit of water when the tank is heating" This could explain the first occurrance after that long shower. The dicharges I've seen in my house probably exceed a pint and a half of water, but nowhere close to a half gallon.

The water heater looks fairly new. It's a Sears model and when I called them they said nobody would talk to me over the phone and that I would have to schedule a service call. Nice.
What's the next step? Thanks for taking the time to reply.

Alex

Ron The Plumber

Thermo expansion takes place on a water heater if pressure reaches 150 psi, at this point the T&P trips allowing water to discharge, this is a safty device, it's not suppose to happen all the time, you should test the pressure on your house, and install an expansion tank as soon as possible. There not that expensive and easy to install. What happens is your house probable has a pressure reducing valve on the water service, this creates a closed system, this not allow water to expand but towards the street that it comes from, when the water heats it expands, if it has no place to expand to, it triggers the T&P, over time if you leave it like it is, the T&P could fail and cause water to always flow from the valve, not good for the pocket book.

Ron

redline

Expansion tank will help. The tank should be less then $75 and then add a few other fittings.

What is the temperature that the water heater is set at? Check the temp as it comes out of the nearest faucet.

If the temperature is excessive (well above 130 degrees) then you may be able to turn the temperature down to the proper level and this may diminish the t/p from draining as often. The higher that the water temp is set then the more expansion will take place in the water heater. Lower temp = less expansion.

Do you know what pressure that your local water dept sends the water out at?

You also have to remember that the pressure from the water dept will fluctuate and may cause this to occur more often.

If you feel that the water heater is older then you could change the t/p valve and see what results from that.

scorrpio

Your TPR valve has a discharge pipe, right? Put a bucket directly under the pipe. While at it, put some kind of pan under the drain cock. Next time you see water, if it's in the bucket, it's from TPR. If in pan, the drain cock is bad. Otherwise, your tank is leaking someplace.

Say, you determined it's from the TPR. Buy a Watts pressure gauge from HD. Costs about $10 and has a red arrow that'll hold highest pressure observed. Connect it to drain cock, open the drain.

Test 1. Turn heater off, open any hot water faucet, let it run for a minute, then close. Watch the gauge. Should come up to about 60-80psi. If goes over 100, you need your pressure regulating valve checked.

Test 2. Leave the gauge on, and use heater as normal. Next time you see water in bucket, check top pressure observed. If it is well under 100, your TPR valve is faulty and needs to be replaced. If around 150psi, TPR is fine.

If you get ~150psi in test 2, but only 60-80 in test 1, looks like you got a backflow preventer and need an expansion tank. Installation is easy - cut a tee into the cold line before the heater, and attach the tank. A 2.2 gal Therm-X-Trol will cost about $40 by itself - not sure what a plumber will charge for the work.