Hi All,
My 1 year old 50gal Gas HW heater has been spewing water from the T&P valve – first an inconsistent dribble, then a consistent dribble… then it would stop. And now it’s gushing at a rate of 2 gal/minute!
Problem used to come and go, and seemed “controllable” by the temp setting, so I reasoned that I just set the T-stat too hot. But we like our water HOT so I kept edging it up past the warm mark.
Then it happened consistently – enough that I had a plumber come in and look, and got a quote for a pressure regulator and expansion tank for over $1200.00. I paused. The problem went away for a while, but now it’s back.
Again, gushing at a 2 gal/min rate, I did a test to see if I could point to either temp OR pressure as a cause: First I moved the temp dial to the lowest setting… after about 24 hours, no change – still gushing. Then I shut off the pilot entirely and let the tank cool. Sure enough, the flow stopped, which leads me to believe it’s temp-related and not pressure-related (so that $1200 investment in a regulator and expansion tank can wait…)
First, is this a fair deduction as to the cause? Secondly, if it IS temp related, and happens even when the dial is set to it’s lowest setting, it this evidence enough that I should replace the T&P valve?
Many thanks for any input and advice.
Jcd
Replies
The relief valve is set to open when either a certain temperature or pressure is reached. The settings are printed on the tag attached to the valve, typically 150 psi and 210°F. One of two things is happening, either you've reached that temperature or pressure, or the relief valve is bad.
Relief valves are cheap, so you could take a guess that the problem is a bad relief valve and change it out for a new one. Or, you could measure the temperature and pressure and see if the valve is reacting properly to elevated conditions.
To measure the temperature, put a thermometer in the water coming out of the relief valve. To measure the pressure, you could screw a pressure gauge to the drain valve (with the correct fittings, of course) and open the valve. If both the temperature and pressure are below the valve settings, but the valve is open, the valve is bad.
If the temperature is too high, the control of the water heater needs to be serviced. If the pressure is too high, but the rest of the house has normal pressure, then you've got a problem with the valving or flow blockage somewhere in your plumbing or with the water heater control.
Under no circumstances should you block off or disable the relief valve or operate without it, even while troubleshooting. It would be very dangerous to do so.
If the plumber recommended a tank and regulator without actually measuring the pressure anywhere to confirm what the problem might be I would be suspicious of his judgement or intentions.
" Then I shut off the pilot entirely and let the tank cool. Sure enough, the flow stopped, which leads me to believe it's temp-related and not pressure-related..."
Not exactly. As the water in the tank heats up, it also expands. And that pressure has to have somewhere to go. You probably have an anti-siphon valve in hour house, so the pressure can't back up into the water system. The only option is for it to blow off the pressure relief valve.
But if the valve is STAYING open - I suspect it's also defective. Was a new one installed when the water heater was put in? If it wasn't, I think that voids your warranty. (But I'm not sure)
I'm not a pro plumber, but this is the deal as far as I know. Hopefully WHW will stop in and offer his opinion.
If you want 1 year of prosperity, grow grain.
If you want 10 years of prosperity, grow trees.
If you want 100 years of prosperity, grow people [old Chinese proverb]
Thanks WAYNELS and Boss Hog for the replies...
On a whim, I went ahead and replaced the T&P valve hoping to eliminate that as a possible cause, well guess what: problem solved! The valve got corroded open I guess - it didn't look like it was in good shape at all.
I thought the new HWH came with a new valve, but if based on Boss Hog's comment they don't, and the old one was used when it was replaced, then that explains alot - the T&P valve was thus 15 years old and not 1!!
I ordered a pressure gauge, so I'll still check the house pressure and remedy with a PRV and expansion tank if needed, but at least for now I'm not spewing water at a 2gal/min rate anymore!
Thanks again,
Jcd
When fixing things that I think I know what's happening but not why, I have a simple rule. This applies to everything, but with vehicles with all the sensors and garbage they have these days, I first get a computer diagnosis. This normally shows either nothing or a half dozen things it could be. I get a complete list of what it could be from all the mechanics in the shop that speak english.
Then I start replacing components starting with the cheapest and work my way up to the most expensive. Sometimes I get lucky and don't have to work my way up very far.
This is the same technique mechanics use- except they start with the most expensive first and work toward the cheapest. Just like your plumber.
Clampman