Gas water heater, Pressure relief valve changed out, still leaks from pipe

Hello all any plumbing experts out here? Noticed my PRV was leaking from the pipe into the pan, drained water heater and installed a new PRV, vacuumed remaining water in pan, few weeks pass and pan is dry, now a very slow drip coming from PRV pipe again, any ideas???? Gas water heater

 

Gas or electric? Whats the temperature set to?

 

Gas, heat set to normal setting, not any higher

 

I’m not a plumbing expert but I stayed at a Holiday Inn Express once, and the hot water almost worked.

I’d connect a pressure gauge on your system and check system pressure. Assuming you have a pressure regulator valve somewhere in the area of the main shut-off (interior / crawlspace), it may be malfunctioning and letting the pressure get too high, thus the leak at your new valve. Note that exterior hose bibs may be plumbed to the main before the regulator, so that might not be the place for a gauge.

Or, your new valve is made from low quality chinesium and might need to be melted down into a higher grade of chinesium. Lots of garbage parts out there these days. I had a new toilet supply line (braided SS) leaking at both crimps just recently.

 

Sorry, no pressure regulator at this house, I'm sure i need one, as for the part I got, it was Home Depot late night before closing hours

 

Sounds like either the gas valve is sticking and is not shutting off the burner once operating temp is reached, or the thermostat is bad.

 

Fairly new WH from HD not even 3 yrs old

 

Anything can happen. All parts are susceptible to go bad. Should be under warranty at least.

 

AI generated .... "The valve opens when the pressure inside the tank exceeds the preset limit, usually 150 psi (pounds per square inch), or the temperature goes above 210 degrees Fahrenheit. Once opened, it allows the excess heated water to flow out of the tank, lowering the internal pressure and temperature."

 

Hmm, yeah, another possibility. If @TXRailRoadBandit73 has a thermometer (meat thermometer works great), it would be easy to check at the tap if it’s getting too darn hot.

For a rough reference, my thermostat is set to the middle of the road, and temp is about 135 - 140F.

I’m still thinking it’s a high pressure issue.

 

This needs to be placed on the cold water line before the WH?

 

Installs on the drain line at the bottom of the tank. Install and open the valve.

 

Just looked at mine and fitting on discharge valve is larger than standard water pressure gauge. Ideally you would want to measure pressure at discharge valve. Gauge will hook up to drain valve but I'm not sure if pressure is different down there.

Probably just a bad valve, did you try opening and closing it a few times?

 

No I have not, I will do this shortly, for how long? Short spurts?

 

Couple of short spurts should do it

 

You have an expansion tank on the cold water supply side, right?

Assuming you do, because you should, the bladder probably failed and the PRV is relieving excess pressure as the water expands with temperature.

 

Check your expansion tank. If it’s lost air, the diaphragm will be flat against the opposite side from the water pressure, leaving no space for expansion when the water heater heats water, this overpressure and your PT valve releases it.

if you turn off your supply and then release water pressure (open a faucet), you should see around 40 lbs on the air valve for your expansion tank. If not, add more air.

 

I don't believe so, I was not at home while install took place

 

if you have an older house, you may not have one. As water utilities now require back flow preventers, homes are required by code to have an expansion tank on the supply side of a tank water heater.

Some jurisdictions don’t require it for tankless heaters, but that sounds like it doesn’t apply to you.

To add, it could be that your tank has a lot of scale or sediment that fouled the new PRV, or you got a defective unit. If your heater if more than 5–7 years old it may be time for replacing.

But if your plumbing system is building pressure because of a missing or failed expansion tank, that needs to be corrected.

 

Usually you don’t have one if you have a well because the supply already has a larger version that maintains pressure and turns the well pump on/off. That tank acts as an expansion tank for the water heater as well, but it can also lose air (some have disphrams, some just an air bubble on top). Again, you can check pressure. If it squirts water, you know there’s no air, so add some.

 

House was made in 60s, WH is in garage in corner on a stand with a drain pain, pipes come out from wall to WH, don't see anything else to it

 

Expansion tank not needed unless required by code.
Original owner of 31 year old house and changed 2 water heaters. The OEM water heater did not have an expansion tank and lasted years ... when it started leaking I had American Home Shield come and swap it out. Dude said I also need expansion tank, earthquake straps, and a gas line moisture trap that AHS won't cover (parts or labor). I said F that and went to Lowes and bought a water heater and all the other crap and installed it myself. AHS did cover the cost of water heater after I sent them the receipt. Then I dropped them.

Long story short, the expansion tank started to leak so I removed it and the water heater lasted for years after that. After the second water tank started to leak I swapped it out again without expansion tank no problems. I still have earthquake straps and moisture trap.

 

Expansion tanks were not required by code 30 years ago because the extra volume of heated water could flow back to the supply system. Now water utilities are required to prevent back flow to prevent contamination of the water supply.

Homes previously on an open system may now be on a closed system, which can cause issues like to OP is experiencing. Just because it’s not required by code doesn’t mean you don’t need one.

 

Thanks all for info

 

Even if the expansion tank or lack thereof is the problem, that will show up on a pressure gauge on the tank, though you might have to watch it until you go crosseyed to see it. The highest pressure would be when the temp gets to the highest just before the burner shuts off.

 

So what you're saying is that water pressure is building up to PRV cracking pressure (150psi) and starting to vent? Since water pressure to a home should be 70-80 psi and slightly higher when heated in the tank. If that was the case the hot water pressure would be remarkably higher coming out of the faucet? I don't know, but we do have back flow prevention on outdoor faucets.

 

You are correct. Doesn't take much expansion in a closed system for water pressure to rise enough to open the relief valve. In fact had this happen recently on my heater, checked the expansion tank pressure, and got water instead of air. Telltale was higher than normal pressure out of the refrigerator water dispenser a week or two before the relief valve started leaking. $40 and 15min to replace expansion tank.

Your outdoor faucets probably have anti-siphon vacuum breakers. Those were required before back flow preventers were mainstream on water supply systems.

 

Makes sense, obviously we have an open loop.

https://youtu.be/S2HVSogYELM?si=-DE5JHUUgG1SLM_9