Gas water heater - PRV problem?

Either a bad pressure relief valve or bad expansion tank if it has one. If it runs like that then a bad pressure relief valve is best guess. A check of the main water pressure wouldn't hurt to see if high water pressure helped the pop off go bad.

Are you on city water or well water?

Where is the water heater?

Unless it is on a concrete floor with a drain next to it, the drip pan is code required in most areas. The drip pan should have a drain running out of it. When you solve the problem dry out the water remaining in it.

If you have city water with a flow check where the water enters the house then a hot water tank needs an expansion tank on the cold water side to give the water a place to go when it expands from heating. It is just a small tank connected to a Tee some where close to the hot water tank.

Usually a bad expansion tank or lack of one will cause the pressure relief valve to drip for a while when the tank is heating the water, but only if you have the backflow preventer on a city water system. Yours sounds like it is running too much for that. Probably a bad pressure relief valve.

Gas `water Heater Problem

`
MERRY CHRISTMAS & HAPPY NEW YEAR ! !
your problems are caused by a couple differnt things,

#1. yes you need T & P valve changed out on your water heater,
these come with a pretensioned spring set at 150 psi. when they have been opened it weaken's the spring so it runs all the time,

#2. to solve the problem you need to have thermal expansion tank installed
above water heater, you can see this on display at most big box stores,
ever time your water heater runs it causes the water to expand. the tank
is 1/2 air that compresses and holds excess hot water till it is used,

#3. you need to get a water pressure guage to test your house water pressure, it should not exceed 80 psi. per your plumbing code, if it go's over 80 psi then you need to look where your main house shut off valve is located to see if you have a PRV. installed and needs replacement ? ? or a new one installed

#4. if you have problems with this then you need to call a "LIC" plumber to take care of problems,

JERRYMAC MASTERPLUMBER

P. S. if you fill you can do this work post back any qustions and we will you
any help we can.

We had a similar question recently. First, you need to understand the difference between pressure regulating valves (PRVs) and Temperature/Pressure relief valves (T/P). If the water supply to your home is too high, it can damage appliances and fixtures in time. The remedy for too high pressure is a PRV which is installed in the water supply line, usually where it comes into the house. This valve not only prevents your water pressure from being too high, it also is a check valve that prevents water from backing up from your house into the city water supply. Here's the reason that is important to know. When your water heater heats water, that water expands. If you do not have a PRV, that expansion is absorbed easily by the city water main. However, with a PRV in place, that water causes a sharp rise in pressure within your water heater. This in turn will trip the T/P valve so as to protect your heater from blowing up. The way this expansion is handled when a PRV is used, is with an expansion tank which is air charged to the same pressure as your PRV. End of problem. This is not to say the T/P valve can't fail, they can, and when they do they are easily and inexpensively replaced. I hope this will help you determine the actual problem in your home.

Prv Problem


Prv's Have A Bypass Built Into The Inside That Allows Water To Push Back Though The Prv.

The City Water Meter On The Other Hand Has A One Way Check Valve Built In To The Supply Valve And Will Not Allow Back Water
Into City Pipes,

So Even If You Do Not Have A Prv. Or Need One For Your House You
Can Still Need A Thermal Expansion Tank Above Your Water Heater
Per Plumbing Code And Mfg's Tank Warranty,



Jerrymac Masterplumber

No intent to start an argument here, but I went for years with a gas water heater, no PRV or expansion tank and had no problems. The very same day I installed a PRV, my TP began to leak. Not knowing any better at the time, I bought a new TP valve but the problem continued. I put a pressure gauge on the hot water line and found that as soon as the water began to heat, the pressure rose until it tripped the TP. As soon as I installed an expansion tank, the problems stopped. Now it is true that newer meters have a check valve built in, but not older ones, but in all of the past discussions, not one person has even suggested that there was a bypass in the PRV. On the contrary, everyone agrees that the PRV has a check valve. Certainly my own experience verifies that at least my PRV has a check valve.

Not all PRV's have a bypass feature...many do not.

The bypass feature of a PRV still allows house side pressure to rise until it equals street pressure, so if your street is over 110 or so, you will still see dripping from the TP.

Prv

It will not drip until the pressure reaches 150 psi, but any leakage caused by expansion will only be a very small amount, about a cupfull total. A leak that becomes a full flow has to be caused by a defective PRV valve and extreme city pressure.