T&P valve draining frequently

[twogooses]

I am having issues with my Water Heater. It's a slantfin tankless boiler (TR-30 PT). It's running on a 4 zone setup. I typically only use one of the zones though. We've been in the home for a year and a half. Towards the end of this winter I started finding a few gallons of water draining from the T&P valve every few days.

I tested the expansion tank and found it to be leaking water from gauge, leading me to believe the diaphram has ruptured and we needed a new one. I bought the same model replacement. An Amtrol #60 and gauges to test our home water pressure and PSI on tank. I attached the water meter to our outside hose line and read about 56 PSI. I then took the precharged (to 12 PSI) new tank and charged it further up to about 55 PSI before installing it. I then removed the old expansion tank to find it almost completely filled with water. Replaced it with the new tank. Turned water line back on and power to water heater. Gave it a day or so.

Now I'm still seeing water, perhaps more. So, even though the exp tank was shot, what else could be causing this? Autofill valve? I don't think the T&P valve is bad as it is draining water once the meter reaches the max level on the valve which is 30 PSI. The slantfin temp range was set at 160 - 180. I lowered this to 140-160 and still same issue.

I then turned on the water from my faucet for a while, and the pressure on slantfin was hovering between 2 and 10. Got the temp on slantfin below 140, down to 120ish. It didn't seem to instantly turn back on, but then turned on the first floor of our home (ZONE 1 of 4), slantfin initiated and watched the gauge on the unit. As it heated the water from 120 to 140 (where min is set) it gradually increased pressure until right about hitting 140 the pressure then hit 30 PSI and T&P valve started draining.

Should I not have charged the new tank? I was under the understanding this needed to be same if not a few PSI below water pressure. Does this change if on a multi-zone house. If using a tankless system?

Should my T&P valve be rated to take on more pressure than 30 PSI?

Should the precharge be the same as the water supply line even if the tank will be placed after a "water pressure regulator valve" set between 12-25 PSI?

Any information would be greatly appreciated. I'm stumped...

 

[Reach4]

You appear to have two systems-- the potable water system, and the boiler system that delivers heat. If the pressure tank you are referring to is part of the boiler system and only sees pressures up to 30 PSI, your precharge should be much less than 55 PSI. I think it should be set to about the point where the system starts refilling, and that may be 12 PSI if I interpret correctly.

 

[Sponsor]

 

[twogooses]

Hey Reach4,

Thanks for your reply. We only have the one system that covers our potable water as well. I've included a picture of our setup that might help.

 

[Reach4]

Since the pressure tank is on the low pressure side of the 12 to 15 PSI regulator, the precharge should be 15 PSI.

 

[twogooses]

silly me...

Should I just shut the system down and relieve pressure on tank until it reads 12-13 or should I remove the tank to do this?

Much appreciated Reach4!

 

[Reach4]

You should bring the water pressure below 12. Then start letting air out. 13 PSI might be better. Ideal would be whatever pressure exists when the regulator starts adding more water.

 

[twogooses]

sorry - re-read your last response. I meant to say relieve pressure until it reads 15 PSI

 

[Reach4]

12, 13, 14... each will be fine. The point is to maximize how much water the tank can accept as the pressure rises due to increased water temperature. I was thinking 14 would do that if the regulator sometimes added water at 13.9 PSI.

 

[twogooses]

Okay - I'm not sure I know how to tell when the regulator starts adding water - I can do some reading up on that. And to think this came pre-charged to 12... ugh - my own fault.

 

[twogooses]

And just to get your 2 cents. From what I described above, do you think that once this is adjusted to the correct level that I shouldn't see any more water on a frequent basis?

Once again, thanks so much - my headache is starting to go away

 

[twogooses]

Okay - I'm not sure I know how to tell when the regulator starts adding water - I can do some reading up on that. And to think this came pre-charged to 12... ugh - my own fault.

Oh right, the regulator in the lineup is set 12-15 so it will add somewhere in-between there. I'm a bit slow on the uptake with plumbing issues.

 

[Reach4]

It is not that critical. If you have a gauge in the boiler water system, and you could look it right after you turn on the water. If you do not have a gauge, but you want to know, you could precharge to 12. Then turn on the water. Measure the pre-charge then. It will have risen to a higher pressure if the regulator delivers a higher pressure. Remember that pressure. That is the pressure your regulator delivers at the current temperature. If the pressure you read is higher than 14, rethink stuff before acting. Do not release air unless the water pressure has first been released to below 12 first.

 

[Jadnashua]

You want your expansion tank precharge to be just below the normal water pressure...when you do that, the bladder is essentially at the resting position, neither pushing out or being pushed in once the boiler is pressurized, and it has the max range to accommodate any expansion.

 

[twogooses]

Hi jadnashua, Thanks for your reply.

Yeah, that's what I originally thought and what I did by setting it just below what our water pressure reading was, but I'm now convinced that is wrong in my setup. Not sure if you looked at my picture/diagram but as it falls in line right after a watts regulator set to 12-15 PSI, it needs to be right around that PSI as Reach4 said. I've changed it to 14 or so (hard to tell exactly on my gauge) and I've had no more T&P draining - although its only been a day, but so far so good. Thanks again for your reply.