PRV Intermittent water dump

Hi everyone, Have a weird problem where I get a intermittent (~3-4 months) water dump from my water heater PRV. Usually it is a pint to quart of water. In between not even a drip. I have had 2 different plumbers to try and resolve the problem. This is a 2 year old water heater in a new house. To make matters worse the pipe from the PRV is stubbed out and dumps directly on to my garage floor. Past homes this line was always stubbed to the outside . The first gentleman came and did water pressure test and said the water pressure was too high. It was 65 PSI and he lowered it to 55PSI after spending an hour hour onsite. He said I have a 50/50 chance that its fixed. Not impressed as the even 65PSI is I believe within limits. I also asked that the PRV drain pipe be plumbed through the garage wall to the outside. His suggestion was to extend the pipe down the side of the inside garage wall and under the garage door, really? Bye.

So I placed a large bowl at the exit of the PRV drain pipe. A couple months after the bowl was full of water. I emptied it and decided to call another plumber and if he could not determine what's wrong just extend the PRV drain pipe to the outside. When he showed up I explained the problem and he went thru the steps of checking all the basics. Water pressure 55PSI, Hot water temp 133F, Expansion tank OK. Since the water dump via the PRV is so intermittent I stated that I can live with that and I would like the PRV drain plumbed to the outside through the adjacent garage wall. He did everything he could to sway me to not extend the PRV drain and suggested I lower the hot water temp to 120F as that could be the problem. When I questioned him he said since I seem to know everything he's done and left.

Am I missing something here? I have owned houses all my life and have had way higher water pressure of 55PSI and probably at least the 133F water temps, maybe higher and have never had problems. Perhaps I should call another plumber and just say I want my PRV drain line plumbed to the outside and NOT even mention the intermittent leak problem.

Any questions, suggestions, comments would be appreciated or should I try door number 3

Thanks!

Is your water heater electric? If so, you cannot lower temperature to 120f, as you may promote growth of legionella bacteria and get sick.

Without being there, I would check a few things.

I would get a gauge, and check your house pressure first thing in the morning before you run ANY water in the house. Your pressure reducing valve could be slowly seeping by, creating high pressures after hours and hours of no use.

I would also bring the size of the expansion tank into question.

Ask around to other neighbors to see if they have an issue. The main may be getting a spike in pressure. I believe you can get gauges before and after the prv that will register spikes.

As I understand it, the problem is with the water heaters P&T Relief valve.
Sounds like he does have a PRV (Pressure Reducing Valve) on his water service.

I guess the question to ask is whether there is an expansion tank in the picture. As well as its size and size of the water heater tank.

Matt30 said:

Is your water heater electric? If so, you cannot lower temperature to 120f, as you may promote growth of legionella bacteria and get sick.

Without being there, I would check a few things.

I would get a gauge, and check your house pressure first thing in the morning before you run ANY water in the house. Your pressure reducing valve could be slowly seeping by, creating high pressures after hours and hours of no use.

I would also bring the size of the expansion tank into question.

Click to expand...

Why do you ask if it's electric? Wouldn't a gas unit be the same if set to produce 120 degree F water?

Diehard said:

Why do you ask if it's electric? Wouldn't a gas unit be the same if set to produce 120 degree F water?

Click to expand...

No because oil/gas units heat directly on the bottom of the tank, where as heating elements and thermostat are inserted like 4” off the bottom, the temperature on the bottom may not be true. Legionella flourishes around 115-120f, so the tanks are set no less than 130f to make sure that space in the bottom doesn’t become a huge petrie dish of bacteria

is the water leaking from A or B ?

They way I understand it, he’s talking about the pressure relief valve. Pressure reducing valves don’t have discharge piping.

Matt30 said:

No because oil/gas units heat directly on the bottom of the tank, where as heating elements and thermostat are inserted like 4” off the bottom, the temperature on the bottom may not be true. Legionella flourishes around 115-120f, so the tanks are set no less than 130f to make sure that space in the bottom doesn’t become a huge petrie dish of bacteria

Click to expand...

That's very interesting and makes sense.

frodo said:

View attachment 20770 is the water leaking from A or B ?

Click to expand...

Its B...but as I said the 1 pint to quart dump is very intermittent. Once every few months. The water heater relief valve does not even drip a drop between events. The unit is gas and about 2 1/2 years old. Bradford White and do have an expansion tank and a previous plumber checked it put and said it was a-ok.

tecwerks said:

Its B...but as I said the 1 pint to quart dump is very intermittent. Once every few months. The water heater relief valve does not even drip a drop between events. The unit is gas and about 2 1/2 years old. Bradford White and do have an expansion tank and a previous plumber checked it put and said it was a-ok.

Click to expand...

Hopefully it wasn't that first plumber you had that checked the expansion tank. The air in the tank must be brought up to the incoming water service pressure while there is no pressure being exerted from the water side.
In other words, close cold water valve feeding the water heater tank, then open the lowest hot water valve to release any pressure while pumping air into tank. It is important to get the maximum amount of air volume into that tank so as to allow the maximum amount of water expansion. Otherwise it's like having an undersized expansion tank. You should also double check that you have the appropriate size tank based on the following...
1. water heater tank size
2. water heater highest temperature setting
3. typical incoming water pressure

I always suspected that but all the 2 plumbers I had come over just checked to see if air was in the tank. I am not able to check it myself as I have mobility issues so I have to rely on $$$ help. I never had an expansion tank ever in my life on any house I owned and the water heaters lasted just fine and I had way better pressure. Why an Expansion tank since there is a Pressure Reducing Valve on the incoming supply from the city? I personally think they are nonsense and nothing but trouble.

Neither of the plumbers used a pressure gauge. They just let some air out to check that air was present. When I questioned this method they got an attitude and left. I am starting to think the plumbers here in North Carolina are incompetent or I am just having bad luck with who i call. Very frustrating.

You can get this gauge at home depot, I included the sku # for easy reference
this gauge will move the red arrow to the highest reading so if you are experiencing a spike in pressure
or if your prv is leaking by, this will let you know that
I suggest that you install this gauge on the boiler drain behind your washing machine
and record the pressure readings in a 24 hour period

Thanks, I will go and purchase one. Does it matter if I put it on the hot or cold line?

try the cold line first

Matt30 said:

No because oil/gas units heat directly on the bottom of the tank, where as heating elements and thermostat are inserted like 4” off the bottom, the temperature on the bottom may not be true. Legionella flourishes around 115-120f, so the tanks are set no less than 130f to make sure that space in the bottom doesn’t become a huge petrie dish of bacteria

Click to expand...

the WHO (World Health Organization) has written a 276 page report on Legionella and is available on-line as a pdf. Legionella thrives (grows) best between about 98 and 107 degF. At about 120 degF, its growth is very limited starting at about 118-122 degF. It also does not grow below about 77 degF. The report also notes that most problems with Legionella growth is with complex water systems, such as in hotels and hospitals. The National Plumbing Code was changed some time back to require ALL water heaters to be set to a minimum of 140 degF, to kill any potential Legionella. Since that temperature is a burn hazard, the code also requires a mixing valve to bring the temperature back down to 120 degF, mixing the "treated" water with the potential source of the Legionella. To kill the Legionella, the water temperature has to be at least 140 degF for 2 minutes (which doesn't work for tankless water heaters). Since a water tank loses heat at a rate directly proportional to the temperature difference, raising the temperature in the tank from 120 to 140 degF will increase the rate of heat loss by about 30%. That is a lot of wasted energy to maybe reduce the unlikely chance of contracting Legionnaire's Disease by a very small amount. The report recommends maintaining water temperature either below 68 degF or above 122 degF.

My code book is my bible. Those are the numbers we go by.

Matt30 said:

My code book is my bible. Those are the numbers we go by.

Click to expand...

I agree with you Matt, The world health org is not an accepted source listed in my code book