Water heater T&P valve issue.
I’ve installed instant hot water circulating loops with no problems in homes with a basement. These used gravity flow (no pump) and had no problems.
My mother had one installed on her house, about a year ago, and now is experiencing a problem. Her house is on a slab, with the plumbing imbedded in the slab. This necessitated running a return line for the circuit through the attic, and installing a pump.
She now has the thermostat set somewhat higher than before. This week she called and said that the T&P valve was leaking. I installed the heater 4 years ago, and thought it odd that the T&P failed, but replaced it. The new valve leaked. That seemed odd, but I had another new valve, so I thought I’d see if that one leaked also. It did.
I’m wondering if anyone sells or rents some kind of data logger to see if we are actually getting a temp or pressure spike. She has fairly high WP, but these valves relieve at 150 psi.
I am perplexed.
Mike
Replies
sometimes they are dripping when the heat is set too high
Is there a check valve or pressure reducer in the system? If so, does the system have an expansion tank?
There is no exp tank but I know there is at least one check. I've put them in gravity systems with no problems, but this has a pump.
Temp is turned up , but well within parameters of the T&P valve. Also no problems for one year of operation-wierd.
Mike
Insert initially amusing but ultimately annoying catch phrase here.
Edited 11/19/2009 5:33 am ET by Junkman001
Mike when water rises in temp its volume expands, & since water does not compress it builds up pressure rather quickly.
You need to have an expansion tank on any closed water heating system wether you have a circulating pump or not.
The probable reason that it took a year to show this problem was trapped air in the system which compressed when the water expanded.
"You need to have an expansion tank on any closed water heating system wether you have a circulating pump or not."What are you talking about? In 60 years I have never lived in or even seen a house, supplied by a municipal water system, that had an expansion tank and I've never had a leaking P&T valve on any of the 6 water heaters in houses where I have lived, nor have any of my relatives or friends. I doubt that any house in California has an expansion tank unless its water is supplied by a well. Is there something very different in the Great North Wet that makes expansion tanks necessary?
BruceT
Are those systems "closed" due to a check valve or pressure regulator on the line coming into the house??
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
"Are those systems "closed" due to a check valve or pressure regulator on the line coming into the house??"Is THAT what you mean by closed? Nope. I'm glad I asked, 'cause I just learned something.ThanksBruceT
As Dan answered "closed" systems are now the norm & that water needs a place to expand when it heats up.
Sorry, I didn't notice that the answer to my question to you was from Dan instead.BruceT
No problem, I was just agreeing with Dan------ sshh don't tell him he might fall over if he found out we agree on something.
Bruce,
They are talking about a hot water space heating system, not a domestic hot water system. There in lies the difference.
Nope. We are talking about a domestic water system.
I've never heard of the need for an expansion tank in a domestic hot water system ... nor a closed loop.
If you have something restricting the backflow in a municipal system, then you need an expansion tank because there is simply no other place for the water to expand into when it is heated.
Most municipal systems don't require a pressure reducing valve or check valve ( at least not in my experience ) so there's no need for any expansion tank in most systems that I have seen.
If you have a well, you already have an expansion tank in the system.
I think there's some confusion here because most recirculating systems require a check valve in the loop to keep the water circulating the right way.
>>>Most municipal systems don't require a pressure reducing valve or check valve ( at least not in my experience ) so there's no need for any expansion tank in most systems that I have seen.<<<
Most codes that I'm aware of REQUIRE a pressure reducing valve if the incomming pressure is above 80psi.
A lot of the municipalities are now requiring an expansion tank whether you have a closed system or not, just info.
"If all else fails, read the directions"
It's very rare in this area to have incoming psi over 80#. I suppose if you are in the hilly areas, that could be a problem and would certainly have to be dealt with. We usually have the opposite problem...not enough water pressure in certain places.
I have never heard of anyone requiring an expansion tank on all systems. That makes absolutely no sense. Why would you want to do that??
Does it have to make sense when you are dealing with a bureaucracy? LOL
"If all else fails, read the directions"
Most codes are changing so that there is some sort of backflow prevention to protect the public water supply from private hook-ups.
In those cases that makes for a "closed system" then an expansion tank is warranted.
Hmm never heard of that, but I'm not really a plumbing expert. I put a PRV in my house ... required as my incoming pressure was like 80+ ... but the BO never mentioned anything about an expansion tank ... which I have on my hydronic heating, but not the domestic side. I don't have a check valve in my hydronic recirc line ... I don't think I've ever seen one in those, either. The pump keeps the water going in the right direction, I think. Not sure why you would need one in a domestic hot water recirc. line, either; the pump should ensure proper water flow and direction, doesn't it? (assuming it is installed in the right location).
Without a check valve in the recirculating line (the check valve is usually located at the bottom of the water heater where the return line is located) you could draw water off the bottom of the tank when you open a hot water faucet.
Sometimes PRVs don't seem to block water from backing up into the water supply. I can't explain it, but I have seen quite a few setups like yours with no expansion tank. I think it has a lot to do with how much hot water you have in the whole system too.
> Sometimes PRVs don't seem to block water from backing up into the water supply. I can't explain it, but I have seen quite a few setups like yours with no expansion tank. I think it has a lot to do with how much hot water you have in the whole system too.I suspect it has more to do with what the pressure is on the other side. Clearly a PRV can't let pressure bleed off if the "high" side is higher than the (overpressure) "low" side.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
Put a pressure gauge on drain cock on Friday. Fluctuates between 90-150. Time for a PRV I think.
MikeInsert initially amusing but ultimately annoying catch phrase here.
You need that tank.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
As noted above over 80psi you need the PRV.
Since it's fluctuating up to 150 means the water has nowhere to expand to, you need an expansion tank.
"As noted above over 80psi you need the PRV."NEED? or suppose to have one.IIRC you are as "guilty" as I am on this one..
William the Geezer, the sequel to Billy the Kid - Shoe
Bill: If you keep putting your criminal activities on the net "THEY" will get you! LOL
"If all else fails, read the directions"
LOL
Well should have one by code anyway.
Also a number of cities and water districts have programs to install check valves at the meter. And often don't warn the residents..
William the Geezer, the sequel to Billy the Kid - Shoe
Probably someone fixed the toilet. Install the expansion tank.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
I agree with the others that you need an expansion tank.
If your dog is barking at the back door and your wife is yelling at the front door, who do you let in first?
The dog, of course, at least he'll shut up after you let him in
I agree that the high likelihood is that you need an expansion tank. But I'd check it with a gauge. If the pressure pops back up right after you run a faucet and then shut it off, then I'd look at the pressure reducing valve on the line into the house. High pressure from water heating on a closed system will be a little more gradual as the pressure runs up.
You can get an inexpensive water pressure gauge to see what the peak pressure is in the system. The one I use is similar to one you can buy at Lowes or HD. The red pointed will indicate the peak pressure. I think you will be surprised at how much the pressure in the system goes up, especially if she already has high water pressure and the temp set high. I have seen a 40 psi increase in a closed system with the heater set to a normal level.
The gauge I've seen at the big box stores is like this one:
http://www.watts.com/pdf/is-276h.pdf
Like has already been said, an expansion tank will probably solve the problem.
Steve
Yep, expansion tank.
Agree with the other posts, expansion tank.
Thanks much for all the replies. I'll be there on Sat doing a chimney repair. Will take a gauge by tomorrow on my way to work, and a exp. tank and sweating stuff on Sat.
I'll post back how it works out.
MikeInsert initially amusing but ultimately annoying catch phrase here.
Check the temps first. P&T valves are designed to dribble on high temp and open on high pressure.
Is the check valve on the recirc line or on the cold water feed line. If it is on the recirc line, it might not be an expansion problem. Take a relief valve too.
We are installing a new h20 heater once or twice a month
I've seen brand new ones leak from the pressure relief valve
Cause was someone setting the temp too high - we turn it down and the leak stops
Good luck!