Water Heater leaks at very specific time of night

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wwhitney

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All of your data so far is consistent with (a) a check valve (or PRV or the like) between the outside hose bib and the water heater and (b) pressure increase from inadequately addressed thermal expansion. And (b) could be either a non-functioning or undersized expansion tank, or the water heater going nuts and overheating the water, like a thermostat failed closed.

Of course, that doesn't explain the 3:00 a.m. timing. If it's just approximately 3:00 a.m., then it could just be consistency on when your last hot water draw is, and the excess pressure taking 6 hours or whatever to build up. But if it's exactly 3:00 a.m. then there must be some timed effect occurring.

John's theory of the municipal water pressure spiking at a consistent time in the night is promising. But if it only spikes to 90 psi (per the one night's reading at the outside hose bib), I don't see how that could directly trigger the T&P. It could raise the baseline pressure to 90 psi, and subsequent uncompensated thermal expansion could get you to 150 psi. If the timing is consistent, that's possible.

Cheers, Wayne
 

John Gayewski

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*Note 6: Water district is Tennessee American Water per the link below. I am unaware of how they operate and could not comment on the existence of water towers, etc. I am within 5 miles of the Tennessee river. Water is plentiful in this area.

Hills and mountains make a big difference.
 

wwhitney

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If it is there the 150 reading last night would prove it is failing.
Not necessarily. If you have a non-bypass PRV set to 60 psi, say, then immediately after any water usage, you should see 60 psi on your gauges. But then when the system is closed, uncompensated thermal expansion could spike the pressure up to 150 psi.

Cheers, Wayne
 

nesappa

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I would still up the air precharge to 73 or 73. You saw 73 on your gauge while dribbling. And is that their max?

Consider talking to the water department about how much pressure they deliver to you. The technical people will like talking about their product.
I am reading about 73 PSI right now at the time of this post. My readings seem more stable inside at the WH drain valve. When it was outside, it seems like I was seeing greater fluctuation and the hold arm seemed more vulnerable to false reading as you described prior.

*Edit, PSI is around 70 right now WHILE dribbling. 73 above was while NO dribbling.
**Edit again, PSI is around 60 right now WHILE dribbling approximately 2 minutes later.

The ET says 150 psi max on the ET itself. The included instructions below do not mention a maximum precharge. Precharge unpacked is 40PSI. I have set this to 60 PSI. I feel like an increase to 73 PSI is safe in this instance.

 

nesappa

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Not necessarily. If you have a non-bypass PRV set to 60 psi, say, then immediately after any water usage, you should see 60 psi on your gauges. But then when the system is closed, uncompensated thermal expansion could spike the pressure up to 150 psi.

Cheers, Wayne
Got it, makes sense.
 

nesappa

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All of your data so far is consistent with (a) a check valve (or PRV or the like) between the outside hose bib and the water heater and (b) pressure increase from inadequately addressed thermal expansion. And (b) could be either a non-functioning or undersized expansion tank, or the water heater going nuts and overheating the water, like a thermostat failed closed.

Of course, that doesn't explain the 3:00 a.m. timing. If it's just approximately 3:00 a.m., then it could just be consistency on when your last hot water draw is, and the excess pressure taking 6 hours or whatever to build up. But if it's exactly 3:00 a.m. then there must be some timed effect occurring.

John's theory of the municipal water pressure spiking at a consistent time in the night is promising. But if it only spikes to 90 psi (per the one night's reading at the outside hose bib), I don't see how that could directly trigger the T&P. It could raise the baseline pressure to 90 psi, and subsequent uncompensated thermal expansion could get you to 150 psi. If the timing is consistent, that's possible.

Cheers, Wayne
For (a) in your post above: are you suggesting the check valve or PRV could be faulty and need replaced? What could a potential remedy be if (a) and (b) are the causes of my problem? Could it be a combination of PRV install or repair along with a larger expansion tank?

Thank You Sir,
 

wwhitney

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For (a) in your post above: are you suggesting the check valve or PRV could be faulty and need replaced?
(a) is not necessarily a problem (unless there's a faulty PRV), it's just a prerequisite for a pressure difference between the hose bib and water heater.

So if (a) isn't true, your T&P or your gauge must be sometimes faulty, since two nights ago you had a 90 psi max reading on the gauge, but the T&P discharged.

I assume you haven't seen unreasonably hot water in the morning? As the T&P could be discharging based on temperature, e.g. if one of your thermostats failed closed. If you have steady significant hot water usage during the day, significant overheating would only occur overnight. [Actually I don't know what temperature they discharge at, it could be a temperature that is only achievable with simultaneous overpressure.]

If you don't have a more important test lined up, it would be useful to do the test of shutting off the water heater overnight, while leaving the gauge at the water heater. That could rule out some corner cases.

Cheers, Wayne
 

nesappa

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(a) is not necessarily a problem (unless there's a faulty PRV), it's just a prerequisite for a pressure difference between the hose bib and water heater.

So if (a) isn't true, your T&P or your gauge must be sometimes faulty, since two nights ago you had a 90 psi max reading on the gauge, but the T&P discharged.

I assume you haven't seen unreasonably hot water in the morning? As the T&P could be discharging based on temperature, e.g. if one of your thermostats failed closed. If you have steady significant hot water usage during the day, significant overheating would only occur overnight. [Actually I don't know what temperature they discharge at, it could be a temperature that is only achievable with simultaneous overpressure.]

If you don't have a more important test lined up, it would be useful to do the test of shutting off the water heater overnight, while leaving the gauge at the water heater. That could rule out some corner cases.

Cheers, Wayne
I will perform this test tonight as it was on the checklist per a prior recommendation as well.

I have not seen particularly hot water in the AM.

Thank You Sir,
 

Reach4

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Watts offers several alternatives for pressure relief. While unlike an expansion tank such products do not prevent against loss of water, they do limit high pressure and prevent issues associated with thermal expansion.

Products include:
  • The 530C calibrated pressure relief valve
  • The LFBRVM1 combination ball valve and relief valve
 

jadnashua

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A PRV with an internal bypass is useless if there's a checkvalve at the meter. It's another failure point. Plus, say your incoming pressure gets to 100psi, your PRV is set to 60, it can't push any water back until it gets to 100psi in your system...defeating the whole purpose of having a PRV in the first place (trying to keep the pressure to a proper level).

Since it's so regular, if your WH isn't on a timer than might turn it on/off, unless you're REALLY anally regular about when and how much hot water you use, it would not be running the WH at exactly 3AM causing that expansion and resulting pressure rise, so it certainly seems like an external force.

If you're up at the time, you could monitor your power meter to verify the WH isn't heating around that time. No water heating going on, any pressure rise would NOT be caused by thermal expansion. Or, flip the breaker off and see if it still happens. If the water was hot when you went to bed, it should still be hot enough for a shower in the morning, just maybe not multiple ones unless you turn it back on first.

Pressure due to elevation change is approximately 0.43#/foot change. If there are hills around, and they are trying to refill a water tower, say the tower was 100' tall, they'd need 43 more pounds of pressure to push water up there than what would normally be supplied during that refill process. If you're at the bottom of a hill, your pressure may be significantly higher than that of a friend that is higher up from the same supply.
 

nesappa

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A PRV with an internal bypass is useless if there's a checkvalve at the meter. It's another failure point. Plus, say your incoming pressure gets to 100psi, your PRV is set to 60, it can't push any water back until it gets to 100psi in your system...defeating the whole purpose of having a PRV in the first place (trying to keep the pressure to a proper level).

Since it's so regular, if your WH isn't on a timer than might turn it on/off, unless you're REALLY anally regular about when and how much hot water you use, it would not be running the WH at exactly 3AM causing that expansion and resulting pressure rise, so it certainly seems like an external force.

If you're up at the time, you could monitor your power meter to verify the WH isn't heating around that time. No water heating going on, any pressure rise would NOT be caused by thermal expansion. Or, flip the breaker off and see if it still happens. If the water was hot when you went to bed, it should still be hot enough for a shower in the morning, just maybe not multiple ones unless you turn it back on first.

Pressure due to elevation change is approximately 0.43#/foot change. If there are hills around, and they are trying to refill a water tower, say the tower was 100' tall, they'd need 43 more pounds of pressure to push water up there than what would normally be supplied during that refill process. If you're at the bottom of a hill, your pressure may be significantly higher than that of a friend that is higher up from the same supply.
Got it, this all is logical to me.

Of note, our water usage is fairly predictable, but not to the standard to cause such specific timing of discharge so I agree there is a high likelihood of external force it would seem to me.
Pressure all day today since 3 AM has been at a cool 60 - 80 PSI. Granted, very little hot water usage. Not a drop of discharge all day. Not one drop. Bucket is 100% dry. You can bet there will be some discharge tonight at 3:01 AM though. (just realized the WH heater will be off tonight so this is not necessarily true. I assume no discharge and excess pressure tonight would indicate I have an ET or WH problem, but hopefully you guys have a good idea there)

*Further note here, I am at the lowest point in this area in terms of elevation.

I am going to safely flip the breaker off after our showers tonight.
This should give us something new to go by here.

Thanks a ton for your insight.
 
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Reach4

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I am going to safely flip the breaker off after our showers tonight.
This should give us something new to go by here.
Leave the gauge in place through the night.

Did you look into time lapse photography for your cellphone?
 

nesappa

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Leave the gauge in place through the night.

Did you look into time lapse photography for your cellphone?
Got it, will leave the guage.

I will have to look into time lapse and see what I have.

Thanks again for the feedback.
 

jadnashua

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I'd wait until the WH has heated the stored water before I shut it off...then, you'll have a full tank in the morning unless you can wait for it to heat up what's left before needing much hot water then. A decent, modern electric WH has decent insulation, and shouldn't lose much temperature overnight. IOW, it shouldn't need to run to bring the water back up to temp unless it might be sitting in a cold garage.

While the WH is heating water, and there's no water use, if the pressure doesn't rise much, it is NOT rising from thermal expansion. If you have an open system with no check valve (a PRV effectively has an internal check valve), the ET wouldn't be needed, and the expanding water would just push back out into the supply system.
 

nesappa

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*Update 01/22/2021.
Water Heater was turned off at the breaker at 8PM.


See below photos taken at 3AM:

1. Pressure rise to 150 PSI indicated. Approximately 1/4 gallon of water discharge.
2. Pressure after 20 seconds or so of dribbling water.
3. Amount of water discharge.

I will be checking they system today for PRV and check valves and will report back at some point.

Does this mean the water heater is not responsible for the thermal expansion?
What implications does this data have?

Thanks,


thumbnail_IMG_1855.jpg
thumbnail_IMG_1856.jpg
thumbnail_IMG_1857.jpg
 

wwhitney

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Does this mean the water heater is not responsible for the thermal expansion?
What implications does this data have?
It certainly means that that water heater is not responsible for the overpressure via thermal expansion. So either it's external, which fits with the timing regularity, or you have a hidden water heater somewhere on a timer. : - ) That is, it's external to the house.

The one piece of data that is inconsistent with the above theory is the night that you got a 90 psi max reading outside at the hose bib. Maybe repeat that test, you should get 150 psi. If so, chalk it up to a fluke.

Then given all of the above, the solution is to install a PRV, or locate and fix the failed PRV that you have.

Cheers, Wayne
 

Reach4

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Amazing! I this is something you will have to deal with, then a PRV is the answer. The PRVs you list in post #20 would be good IMO if you have a good section of 3/4 inch copper to insert the PRV. You might consider having the PRV after where the outdoor spigots connect.

BUT, I would have a priority talk with the water department/company. They may have had a failure and should never have been sending these pressure spikes. Yes, their answer could be tough, deal with it, but they might thank you for the info and fix it.

Your neighbors that are at about your altitude would probably have been seeing this symptom too.

Each of the PRVs will have a debris screen, and for the ones you selected the screen is part of the cartridge. Typically that screen can be cleaned. It is possible to put a wye filter as a pre-screen, and that might be easier to clean. But also you will want a valve as the first thing in the path. I expect you have the valve in a good spot already.
 
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wwhitney

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BTW, if you need complete proof that the pressure spike is coming in from the water supply (e.g. in dealing with the water company), you can try the test of shutting off your main water supply overnight, keeping the gauge at the water heater. You just have to be sure not to use any water during the test. The pressure at the end of the test should match the starting pressure, possibly with some change up or down due to the water heater running a little, or some of the hot water pipes cooling off. But no spike to 150 psi.

Cheers, Wayne
 

Jeff H Young

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great solved it you need a prv. 150 psi with no water heater isnt thermal expansion. so 150 means you n eed a reg..
 

nesappa

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*Update #2 01/22/2022

Thanks again for all of the feedback guys it means a lot to my family and myself. I am very grateful to you all.

I verified today that there IS in fact a PRV. It is after the water meter and before every single thing in the house it appears. It is the first thing I see where my water line comes into my crawlspace.

It is a zurn. It appears to be relatively recent, maybe installed this decade.

Per Reach4 post above I may look into cleaning or rebuilding one, or just installing new.

per wwhitney above I believe I will shut the water main off and test the pressure one of these nights this weekend. This is a great idea and can help confirm the source of the increase in pressure so i understand what you mean here. I will also retest at the outside faucet. I do suspect a fluke here as the "hold" hand of the gauge is very easily affected by vibration as Reach4 suggested also.

Since there is a PRV, I am tentatively concluding that this was the true failure that led to all of the symptoms that resulted in the new T&P and ET unnecessarily. They were old enough so I am not sweating that and I feel much better about the walls, floors, and general installation of the things I replaced along the way.

Hope I am in the home stretch here.

Thanks again everyone and please hang around as I hope to land this one with a rebuilt or new PRV.

Have a great weekend!
 
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