Leaking Indirect Water Heater Relief Valve - stumped

agaisin

Hi - have a hydronic water system for heating house, and an indirect water heater for the hot water to the house. Noticed the Bock 30CT relief valve leaking and replaced with a similarly spec'd relief valve (was Watts LL100XL, replaced with Cash Acme NCLX-LS both 150psi/210F and ~100k BTU max input.
Now overnight have more water coming out of the new relief valve. Not a consistent drip but water definitely collected there (presumably when boiler had to run again maybe after heavy hot water use).
I assume the HW relief valve is good.
On well - checked the well pressure tank and the boiler expansion tank - both checked out without failed bladder (no water coming out of nipple and had plenty air in em. HFT-30 for the boiler expansion tank had >10 psi.
The water temperature coming out of system is ~118, so don't think it's thermostat failure or DHW would be too hot leading to too high pressure right?
What else could it be, what else do I need to check...

Thanks in advance!

mattmia2

Does the well tank have a pressure gauge on the water side? Is there anything like a thermostatic valve or a check valve or a recirculating pump between the well tank and the water heater?

Karl Reynolds

Could likely be a leak in the coil of the Bock tank, allowing house pressure DHW water into the storage tank blowing the relief. Should probably be a DHW expansion tank on the water heater too.

agaisin

mattmia2 said:

Does the well tank have a pressure gauge on the water side? Is there anything like a thermostatic valve or a check valve or a recirculating pump between the well tank and the water heater?

Yes - well tank has a pressure gauge on the water side.
No expert so I may not be answering to your satisfaction. Lake fed jet pump goes through filters and uv to cold water inlet for the indirect water heater. check valve between pump and lake intake. no check valve or circulation pump between well tanka and water heater at least not directly. There's a make up water feed from cold to boiler with a backflow preventer and pressure regulator. of course there's zone controls and a circulation pump on the boiler side but unless some other issue, as i understand the boiler system and DHW should be isolated.
Does that make sense/answer your q?

mattmia2

The relief valve is in the domestic hot water side of the tank, right?

agaisin

Karl Reynolds said:

Could likely be a leak in the coil of the Bock tank, allowing house pressure DHW water into the storage tank blowing the relief. Should probably be a DHW expansion tank on the water heater too.

So - my leak is on the Bock tank. My understanding is that since Bock tank pressure will always be higher than the boiler pressure. If there were a leak in the coil, as I understand it, the boiler's relief valve would go off well before the Indirect Water heater/Bock relief valve, right?
Also - I have an expansion tank on the boiler side and pressure tank for well water on the house side. Iiuc since I have a pressure tank on the well side, no need for a separate expansion tank? Those are the only two pressure tanks so if I need another then it's never had it and don't think we had leaking before at that point. (only live here seasonally and still < 2 years ownership but at least during that time...).

agaisin

mattmia2 said:

The relief valve is in the domestic hot water side of the tank, right?

Correct - relief valve that's leaking is on the DHW side of the tank, Bock 30CT.

nekdahl

Agree with Karl, if there is a backflow preventer on the water supply to the tank it could be over pressurizing and thus blowing relief valve. Adding a DHW thermal expansion tank such as a B&G PT-12 will give the water a place to expand before goes out the relief valve.

mattmia2

What does the gauge on the well tank say? Maybe look at it first thing in the morning before any fixtures are opened. Really the only options here are the well tank is bad/not properly charged, the pressuretrol is sometimes sticking and not shutting off the well pump, or the boiler is heating at least the part of the tank where the probe for the relief valve is up to 210 and it is blowing off on temp.

agaisin

nekdahl said:

Agree with Karl, if there is a backflow preventer on the water supply to the tank it could be over pressurizing and thus blowing relief valve. Adding a DHW thermal expansion tank such as a B&G PT-12 will give the water a place to expand before goes out the relief valve.

Not sure I'm following. As I understand my system, there is a backflow preventer from the cold in on DHW heater to the boiler on the make up water line, presumably to prevent boiler water from backflowing to the DHW. But there is no backflow preventer I know of between my well system/pump/tank and the DHW Bock Tank.

mattmia2

Maybe the diaphragm in the well tank can stick to the inside of the outer tank well enough to not move.

agaisin

mattmia2 said:

Maybe the diaphragm in the well tank can stick to the inside of the outer tank well enough to not move.

Interesting - there's definitely air in the well tank. I didn't drain it before testing so the water was at 45 and the air pressure was also at 45. If the air is not to spec, then perhaps it's not having the necessary effect? What's next step, I should drain the house side to 0 psi water pressure and then recheck the tank psi and make sure it's spec (30-50 cutout so should be 28 iiuc)?

agaisin

mattmia2 said:

What does the gauge on the well tank say? Maybe look at it first thing in the morning before any fixtures are opened. Really the only options here are the well tank is bad/not properly charged, the pressuretrol is sometimes sticking and not shutting off the well pump, or the boiler is heating at least the part of the tank where the probe for the relief valve is up to 210 and it is blowing off on temp.

What's pressuretrol? sorry new to lingo so not sure if that's a thing or typo.
I will check first thing in am after overnight.
I will also get tank to 0psi water and re-check the tank's bladder psi.
I will also try to get a water pressure tester with the second pointer that shows max pressure (Do i connect to like an outdoor hose bib?). Thing I don't get is I think the well tank psi would be reading way higher than 50 first thing in the am.... if the pressure got that high?... Guess that's your point to check first thing in am?

mattmia2

The pressuretrol is the pressure switch that controls the well pump. A gauge with a garden hose connection could connect to an outdoor hose bib or any convienent boiler drain on the domestic water system.

agaisin

Well - I drained the well pressure tank and now the pressure reading was at best ~15 when it should be 28 (2 psi lower than cut in and it's a 30/50). Got two diff readings on the bike pump guage vs. a quality tire guage. I pumped it back up to 28 (more pumps than i expected lol). Perhaps that could explain it - if there wasn't enough pressure then it didn't have enough room for expansion. if it were completely failed i would have had more water, but if it were functioning as it should i shouldn't have had any?...

agaisin

mattmia2 said:

What does the gauge on the well tank say? Maybe look at it first thing in the morning before any fixtures are opened. Really the only options here are the well tank is bad/not properly charged, the pressuretrol is sometimes sticking and not shutting off the well pump, or the boiler is heating at least the part of the tank where the probe for the relief valve is up to 210 and it is blowing off on temp.

Thank you so much for the tips/advice!! At least problem #1 the well tank wasn't fully charged. I tried to charge it back up to 28 psi, will see if it holds and if the relief continues to leak or not. Thanks!!

How normal is it to have to recharge the tanks, is that a sign it's failed or over time they'll normally lose some charge?

Larry Weingarten

Hi, If you continue to have problems, get a pressure gauge, something like this one and leave it on the drain valve of the tank. It will tell you just how high the pressure got and help you to figure out what and when it happens.


Yours, Larry

mattmia2

agaisin said:

How normal is it to have to recharge the tanks, is that a sign it's failed or over time they'll normally lose some charge?

Some amount of gas can permeate through the diaphragm material and frequently schrader valves don't seal perfectly so it isn't unusual for a diaphragm tank to lose its charge over time. I think the manufacturer recommends it be checked once a year.

agaisin

Thanks all for your help - after updating charge on the pressure tank overnight (after 2 adult showers), no water in the pot and max pressure of 140. Will keep monitoring and see if there's water in there and what the max pressure was.
Some follow up questions:
1) Iiuc I have no backflow preventer or check valve b/w the well pressure tank and the Indirect DHW, so I would have expected that the current pressure on Indirect DHW and current water pressure at well pressure tank should always match (aside from gauge inaccuracy). Right?
2) If above is true, then if my max indirect was 140 and my whole house filters and other components in the plumbing aren't really designed for 140+ pressure right? Granted it's probably not sustained high pressure but will it damage anything?
3) following logic above, is it standard practice in my case with well pressure tank and indirect DHW, to still add a separate/purpose built expansion tank and maybe even a backflow preventer or check valve (difference?) on the cold water intake for indirect DHW to avoid high pressures damaging the plumbing on the cold side? I guess in the same vein even if i had a check valve on cold side the hot side could get to 140+ psi at times. Is this not an issue?

Thanks all for your inputs above, hopefully I've isolated the problem to well pressure tank charge and have a much better understanding of my systems. What an amazing/knowledgeable group.

mattmia2

where are you measuring the 140 psig?

agaisin

mattmia2 said:

where are you measuring the 140 psig?

Off the Indirect Water Heater drain

mattmia2

What if you put it somewhere else in the system on the cold water supply? I suspect it is a problem with the well controls. Either that or there is some sort of a check valve. My suspicion is the pump controls aren't working right and the relief valve on the water heater is where that pressure is being relieved.
Another way to test the well tank would be to open a faucet and let it run a moment and make sure the pressure doesn't fall much with only a small draw and the pump not running. If the tank isn't taking any water the pressure will plummet when you let a little bit of water out.

agaisin

In general the pump has been functioning well afaik - it's a 30/50 and cuts in at 30 and out at 50. Have never seen a current pressure above 50 on the pump side. Is it a problem that I reached 140psi overnight or after heater kicked in after showers or is 140psi totally normal? If that's normal i.e. <150 I'm good. If the psi should never be that high then I guess I need to keep looking and then the q is what's causing high pressures and where. Generally the current pressure on DHW and Pump guage are matching. They were off by a few psi maybe at most.

agaisin

mattmia2 said:

What if you put it somewhere else in the system on the cold water supply? I suspect it is a problem with the well controls. Either that or there is some sort of a check valve. My suspicion is the pump controls aren't working right and the relief valve on the water heater is where that pressure is being relieved.
Another way to test the well tank would be to open a faucet and let it run a moment and make sure the pressure doesn't fall much with only a small draw and the pump not running. If the tank isn't taking any water the pressure will plummet when you let a little bit of water out.

In general the pump/well controls seem to work great afaik. The pump isn't constantly running, only after a few flushes, during showering, after lots of sink use. Can double check though.

agaisin

So - is 140psi max on the red arm of gauge a problem? The temperature of lake water is 64, getting heated to ~120. The indirect DHW is a 30 gallon. Guess I'm not clear on whether there's a problem with max psi of 140 considering it could have been momentary...? between the pump and the indirect DHW is a manifold, uv viqua d4, two water filter cartridges, and the pump. No other check valve or hardware I'm aware of or can see. Will double check.

Jamie Hall

140 is getting to the point where things can be damaged. Hence the ppressure relief valve -- it's doing what it's supposed to do.

With your pressure switch set at 30/50, and a functioning well pump control tank, you should never see the pressure anywhere in the domestic water system much over 50, nor much under 30, when nothing is running. A very large draw -- greater than what the pump can manage alone, may drop the pressure below 30, and the pressure at the taps may be less simply due to friction losses.

Now all that said, the only way you can get pressure much over the pump cutout is either be a water hammer problem -- locally, when the flow is rapidly stopped -- which most likely would hear, or by there being a valve in the system which prevents water from flowing from the hot water heater and piping back to the well pump control tank. On a system with a well pump, there shouldn't be one. This valve might be a check valve or a backflow preventer -- for the purposes of this problem, they will cause the same difficulty.

Therefore I suggest that you go over the piping very carefully and locate any and all valves between the well pump control tank and the hot water heater. Somewhere in there -- it may be hard to find -- you may find the culprit. Check that UV Aqua very carefully -- there may be a backflow preventer or check valve in it, or it may (or the filters may) be arranged and built in such a way that they prevent backflow, just like a check valve, though without intending to.

agaisin

to be clear - on the indirect water heater, what’s the normal mac pressure when it’s reheating the full 30 gallons. and on the heater side what else would cause it to over pressurize? there’s a backflow preventer and a pressure regulator/autofill valve b/w the indirect dhw and boiler for makeup water iiuc.
if well pump side is fine, what else to look at on the heat side - thermostat on the indirect dhw, fill valve not fully closing letting more water in than it should? I guess maybe i can isolate pressure tank from the indirect dhw…

mattmia2

The max pressure should be around 50 psig if the cutout of the pressuretrol is 50 psig. The well tank should absorb the expansion of the water as it is heated.

If the pressure on the dhw side is getting to 150 psig that is the problem, the problem isn't on the domestic heating side. The well tank isn't absorbing the expansion from heating the water for some reason. It may be that the precharge in the well tank is still too low and the diaphragm is fully expanded when the well pump cuts out so that it can't absorb any more volume as the indirect heats.

agaisin

I'll recheck the well pressure tank charge. maybe it didn't hold pressure. Also - was wondering about that - unlike the normal expansion tank, the pressure tank can be in 2 states - water pressure at 31ps or water pressure at 50psi. If it's at 50psi, there's not as much room for expansion - is there enough?... But then in general with well systems, would expect that you should always have a separate expansion tank even though there's also a pressure tank. Can't find anything definitive about standard practice...

mattmia2

The well tank will act as the expansion tank if there is no check valve between the dhw tank and the well tank. It has been that way ever since water heaters existed.

agaisin

mattmia2 said:

The well tank will act as the expansion tank if there is no check valve between the dhw tank and the well tank. It has been that way ever since water heaters existed.

So I guess one thing i can do is add another water pressure tester to the well pressure tank and confirm that the highs on both Indirect Heater and Well Pressure tank match or not. If they match then there's no check valve or backflow preventer b/w them, still need to figure out what's causing the high pressure. Is it possible it could just be water hammer?

Jamie Hall

There is a remote chance that your well pump pressure tank isn't large enough. Its size is based -- or should be based -- on the well pump flow rating. Check it this way; Draw water off somewhere until the pump starts and immediately start timing and at the same time shut off the water flow completely. The pump should take at least a minute to bring the pressure up from 30 to 50 psi. If it takes less, either the tank is too small -- or it's waterlogged.

And it doesn't exist in two states. Assuming your start at 50 with the pump off, as you draw water the pressure drops (the water you are drawing is coming from the tank -- not the well). Eventually, the pressure drops to 30 and the pump turns on. Now the pressure will slowly rise, assuming the pump delivery is greater than your water flow, as the extra water from the pump is refilling the tank. When the pressure gets to 50, the pump shuts off.

agaisin

Jamie Hall said:

There is a remote chance that your well pump pressure tank isn't large enough. Its size is based -- or should be based -- on the well pump flow rating. Check it this way; Draw water off somewhere until the pump starts and immediately start timing and at the same time shut off the water flow completely. The pump should take at least a minute to bring the pressure up from 30 to 50 psi. If it takes less, either the tank is too small -- or it's waterlogged.

And it doesn't exist in two states. Assuming your start at 50 with the pump off, as you draw water the pressure drops (the water you are drawing is coming from the tank -- not the well). Eventually, the pressure drops to 30 and the pump turns on. Now the pressure will slowly rise, assuming the pump delivery is greater than your water flow, as the extra water from the pump is refilling the tank. When the pressure gets to 50, the pump shuts off.

Yep - it's a Gould's J5S with a Goulds V60 20 gallon pressure tank. I'm on the assumption that the problem with high pressure is either pressure tank's bladder is low/shot or something on the indirect hot water side overheating or overfilling the tank and reaching high pressure. I don't believe it's the well pump overpressurizing - it's never held higher than 50 the cutout set point...

Larry Weingarten

Hi, I’m not sure anyone has explained the source of the high pressure. It’s almost certainly thermal expansion caused by heating water in the tank. It’s pretty much an unstoppable force. The water gets bigger and needs a place to flow back to. That’s why you need an unobstructed path back to the well tank. 140 psi will damage things, or at a minimum, shorten their life. Supply lines under sinks just love to burst as Mad Dog will tell you 😉

Yours, Larry

agaisin

So - emptied the well pressure tank again and confirmed it had air, don’t think it lost any air since yesterday. It definitely isn’t collapsed or anything based on holding air pressure and of course knock test. Also - when i emptied the well pressure tank down to 0 psi water pressure the indirect water heater pressure also went down to 0. isn’t that a proof point thT there is not a backflow preventer or check valve bc of there was i would have expected the pressure on the heater to stay at status quo until the hot water gets used, not from cold side pressure coming down… So if i have functional pressure tank what could allow heater pressure to rise so high to 140psi? Hot Water out of faucet temp is only going to 118. Could it be that if well pressure tank is at 50 psi there’s not enough room for the indirect hot water’s 30 gallon tank’s thermal expansion (bock 30ct)? the pressure tank is 20 gallon but that translates to 6 gallon drawdown at 30/50…

mattmia2

If the precharge is too low in the well tank the diaphragm will be completely full when the well pump cuts out so there will be no room for expansion when the water in the water heater expands. i think it needs to be at or close to the cutout pressure but i was hoping someone that knows more about well tanks would answer that. you could always resort to reading the instructions.

agaisin

mattmia2 said:

If the precharge is too low in the well tank the diaphragm will be completely full when the well pump cuts out so there will be no room for expansion when the water in the water heater expands. i think it needs to be at or close to the cutout pressure but i was hoping someone that knows more about well tanks would answer that. you could always resort to reading the instructions.

the instructions for what - for the well pressure tank the instructions are 2 psi lower than cutin pressure. im at 30/50 so precharge is 28. thing is that is accounting for well pump use not expansion tank use for heater. i’m not finding any formal guidance on using pressure tank also as the expansion tank… so i question if tank is full at cutout pressure is there really room fir it to be used as expansion tank fir the (30g) indirect heater? i believe that is not a documented use case…and now i question if it’s officially supported/designed for it.

Jamie Hall

The well tank must be precharged to the pump cutin pressure less 2 psi, as you said. That precharge must be done with the tank drained and disconnected from the system (you can use a tire pump or air compressor). Pressure tanks for well pumps can and indeed usually are used without difficulty on water systems containing hot water heaters (of any kind). You can -- and should -- check the air pressure in the tank both at cutout and cutin. You can use a regular tire pressure gauge on the Schrader valve at the air end. The air pressure you read should be exactly the same as the water pressure in the system.

Now. It seems to me you are missing something in the logic. The pump cutout pressure is 50 psi, and you have verified that. There is absolutely no way that the pump can create a higher pressure in your system. In fact, as I recall that pump can't reach that pressure even with the outlet completely closed off. So the pressure is coming from somewhere else, and the only source you have is the expansion of the hot water.

agaisin

i’m back to stumped. the pressure tank has correct precharge of 28 when empty. no check valve or backflow be the pressure tank and indirect water heater, yet the water pressure teat gauge registered a max of 140 overnight presumably from thermal expansion when large volume of water was being reheated (after 2 showers). pressure tank should have ’absorbed’ the expansion. hot water out of faucet is 118 (not too hot). i looked at manual for my filter cartridges and viqua d4 and no mention of check valve or backflow built in, and saw that when well tank was 0 the indirect water heater pressure went down to 0 so also evidence of no check valve preventing backflow… not sure what else to check.

mattmia2

Move the gauge with the max reading pointer to a boiler drain or faucet near the well tank and wait overnight again.

Jamie Hall

mattmia2 said:

Move the gauge with the max reading pointer to a boiler drain or faucet near the well tank and wait overnight again.

And make sure there are no valves or widgets of any kind between the gauge and the well pressure tank.