Water heater T&P valve problems
- Thread starter Wanderwind
- Start date
That's why I'm encouraging him to take readings to confirm. I've studied his photo, and there doesn't appear to be a check valve in the cold water supply line to the water heater (where most would recommend placing one). There may be a trick fitting, or wafer insert, or some other sneaky install, but it's not obvious.
@Wanderwind seems pretty sharp. I think he would have found the check valve right off if it was even remotely evident.
@Wanderwind seems pretty sharp. I think he would have found the check valve right off if it was even remotely evident.
@Wanderwind,
Suggest putting the gauge on the water heater drain valve connection (hose threads). Open the valve to read the cold tank pressure, then turn on the heater. You can watch the pressure as the tank heats up. When it stabilizes (hopefully at a higher pressure), turn on a cold water faucet while someone watches the gauge. If the tank pressure doesn't change while the cold water is running, there is a check valve. However, if running cold water changes the tank pressure, there is no check valve and some other phenomenon is responsible for the flow difference you observed.
That one test will tell you what your regulator is supplying; whether you have a mystery check valve, and how high your system pressure is going during warm-up. You can then decide whether an additional expansion tank is necessary.
If you put a hose extension on the drain valve for convenience, make certain it is rated for the pressure you will expose it to. If your relief is popping at 150 or higher, that will bust a cheap garden hose and make a real mess of your boat. Keep any hose as short as possible to keep distortion of data to a minimum.
Suggest putting the gauge on the water heater drain valve connection (hose threads). Open the valve to read the cold tank pressure, then turn on the heater. You can watch the pressure as the tank heats up. When it stabilizes (hopefully at a higher pressure), turn on a cold water faucet while someone watches the gauge. If the tank pressure doesn't change while the cold water is running, there is a check valve. However, if running cold water changes the tank pressure, there is no check valve and some other phenomenon is responsible for the flow difference you observed.
That one test will tell you what your regulator is supplying; whether you have a mystery check valve, and how high your system pressure is going during warm-up. You can then decide whether an additional expansion tank is necessary.
If you put a hose extension on the drain valve for convenience, make certain it is rated for the pressure you will expose it to. If your relief is popping at 150 or higher, that will bust a cheap garden hose and make a real mess of your boat. Keep any hose as short as possible to keep distortion of data to a minimum.
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No T&P hose and no need for one here. Whatever comes out of it, if ever anything, will drain into the bilge through limber holes and discharged by the bilge pump.
There is something odd here, and you mentioned something in your post.
You said that the T&P hose was missing, and you added it.
Well, I can’t figure out why it’s connected into your cold water T. It should just be drained to bilge.
I’m going to go out on a limb here and suggest the reason it’s leaking is because of the system pressure being fed back into it.
Anybody wanna comment on this???
Thinking about this more, I believe your accumulator is putting a burst of pressure back through the T&P valve. Once the accumulator has dumped its bladder pressure, there is no more surge.
No hose on the T&P valve can result in spraying scalding water on persons and equipment nearby, if it ever opens.
Interesting thought. That device is installed to take the pulses out when running the pump, and to absorb minor volume variations. He wisely raised the bladder pressure to try to use it for an "expansion tank" duty while on city water. It just wasn't large enough for the application.
I agree that the accumulator might hold the pressure higher, momentarily, when flow starts. That is part of why it's there.
Your theory seems to support the existence of a check valve in the hot water, if the accumulator was installed behind the check valve (tank side). But if you look at the photo, the accumulator is on the water supply line BEFORE the tee. Based on position, it SEEMS he should see the same spurt on both hot and cold.
Also, the accumulator can only feedback pressure that has charged it. So if the dock is supplying 40 psi, the accumulator will only have 40psi available, and only briefly. The dock is supplying an endless amount of 40psi (or whatever it really is) water. Once flow starts, pressure drop through pipes and fittings comes into it. Even something as simple as different fittings/accessories on hot vs cold could account for the difference in flow he's seeing. But without knowing the piping and accessory layout, it's hard to diagnose.
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Think you misinterpreted what he wrote. The T&P discharge hose isn't connected back to the system.
Hmm. Interesting. Are our water heaters in different places? Mine is under the port side settee, just forward of the locker next to the nav station. Below the side of the water heater with the T&P valve is teak/holly cabin sole. (As in the picture I posted earlier)
When I had no hose, any water that came out of the T&P valve would run out on the cabin sole under the edge of the settee.
Right, it's not. The "cold T" I was referring to is where the pressurized cold water from the pump/accumulator splits and one side goes to the water heater and the other to the rest of the cold fixtures on the boat.
Daniel.
I’ve read this thread and it seems that there is a lot going on in what should be a simple system. Here is a basic diagram for a water system.
You state that
If this was my problem I’d simplify the issues. I would try to isolate the problem by adding one thing at a time.
Hope this helps.
I’ve read this thread and it seems that there is a lot going on in what should be a simple system. Here is a basic diagram for a water system.
You state that
- your system has not worked right for 3 years.
- That the boat and system is 25 years old.
- You replaced a bad thermostat (assumption is it was on the water heater not your engine)
- You have a cheap “RV water regulator”
- You pumped up the accumulator to 45psi
- That your T&P valve leaks
- That the hot water side of the system spurts water on the hot side not the cold side in the sink.
- That your worried about possible check valves.
If this was my problem I’d simplify the issues. I would try to isolate the problem by adding one thing at a time.
- That Remove the city water hook up from the system after being sure the onboard water tank is full.
- Turn off the heater on the water heater. Run only cold water in the system.
- Turn off the water pressure pump.
- Open up all the faucets to 0 the pressure in the system.
- Close all the faucets.
- Now your system should be at Zero pressure and cold with water in the system.
- Turn in the boats water pump to pressure the system. Then go to each sink one at a time and open first the hot water faucet . Examine the way the water flows. Shut the faucet. Let the pump bring the pressure up till it stops. Then open the cold water faucet. Compare the two water streams. Check the T&P valve on the water heater. Has there been any leaking.
- Now you have a base line.
- Next add the city water line to the system. Follow the testing in step 7.
- Next add the water heater electrical system. Follow the testing in step 7.
- Finally turn off the electrical system to the water heater and start your engine to test the engine heating of the water. When the engine has heated the water for about an hour (time enough to take the boat out and practicing your docking skills). Follow the testing in step 7.
Hope this helps.
Thanks to all of you for encouraging me to be more scientific about this... I did an experiment this morning.
Frankly, I aborted the test because the readings started to scare me...
Yesterday I got a pressure gauge with a GHT connector, and a adapter from 1/2" MIP to GHT (male). I first used the GHT to the hose bib after the pressure regulator to check pressure coming into the boat and got 36psi. Then I attached the adapter and connected it to the 1/2" hose that connects the shower spray nozzle. This way I can easily test the pressure on the hot and cold side by using the shower valves. I know I'll lose some pressure by taking the reading this way, so it may affect the integrity of the test.
First, with the WH off, I ran the galley hot tap until the water coming out was completely cold. Then I took my first baseline measurements and turned on the WH. Planned to check the pressure every 10 minutes.
I always tested the cold first because I wanted to test the hypothesis that the high pressure on the hot side was absent on the cold side.
Time Cold Hot
T0:00 35 35
T0:10 35 70
T0:20 35 35
T0:30 35 96
The T0:20 reading seems like an anomaly. All I can think is that I may have fudged up the reading somehow by relieving the pressure accidentally when I was taking the reading.
At T0:30, I aborted the test because the shower hose flexed violently when I opened the shower valve. Made me think it was at risk of bursting. So, if I want to test further I'll need to plumb the pressure gauge into the plumbing more directly. I'm not sure further testing is necessary, however.
The water is fairly hot. I don't have a thermometer but my completely unscientific "hand test" says somewhere around 130F. (I should get a thermometer.)
Also, no water leaked from the T&P valve during this test.
So... Still confused... Still don't see a check valve, but clearly the pressure is different. Attached is a diagram of the components I can see and their connections.
The "Boat Fixtures" box is basically the rest of the boat -- the stuff I can't see. As far as I can tell, there cannot be a check valve anywhere in there as water comes both ways via the line marked "C" depending on if running on city water or using the tanks.
I'm not really sure what the next step is here. All I can think of doing is disassembling the cold side to find the check valve, (or confirm that there isn't one).
Frankly, I aborted the test because the readings started to scare me...
Yesterday I got a pressure gauge with a GHT connector, and a adapter from 1/2" MIP to GHT (male). I first used the GHT to the hose bib after the pressure regulator to check pressure coming into the boat and got 36psi. Then I attached the adapter and connected it to the 1/2" hose that connects the shower spray nozzle. This way I can easily test the pressure on the hot and cold side by using the shower valves. I know I'll lose some pressure by taking the reading this way, so it may affect the integrity of the test.
First, with the WH off, I ran the galley hot tap until the water coming out was completely cold. Then I took my first baseline measurements and turned on the WH. Planned to check the pressure every 10 minutes.
I always tested the cold first because I wanted to test the hypothesis that the high pressure on the hot side was absent on the cold side.
Time Cold Hot
T0:00 35 35
T0:10 35 70
T0:20 35 35
T0:30 35 96
The T0:20 reading seems like an anomaly. All I can think is that I may have fudged up the reading somehow by relieving the pressure accidentally when I was taking the reading.
At T0:30, I aborted the test because the shower hose flexed violently when I opened the shower valve. Made me think it was at risk of bursting. So, if I want to test further I'll need to plumb the pressure gauge into the plumbing more directly. I'm not sure further testing is necessary, however.
The water is fairly hot. I don't have a thermometer but my completely unscientific "hand test" says somewhere around 130F. (I should get a thermometer.)
Also, no water leaked from the T&P valve during this test.
So... Still confused... Still don't see a check valve, but clearly the pressure is different. Attached is a diagram of the components I can see and their connections.
The "Boat Fixtures" box is basically the rest of the boat -- the stuff I can't see. As far as I can tell, there cannot be a check valve anywhere in there as water comes both ways via the line marked "C" depending on if running on city water or using the tanks.
I'm not really sure what the next step is here. All I can think of doing is disassembling the cold side to find the check valve, (or confirm that there isn't one).
Attachments
Holy crap. I really appreciate you taking the time to come up with this diagnostic procedure. It's going to take me some time to work through...
I hadn't thought about the engine heat exchanger. As far as I know, the engine heating the water has never caused the T&P valve to leak. We motored 8-10 hours down the ICW about a month ago, had hot water, no T&P drips...
Two things I noticed about the system diagram you posted:
1) It shows a check-valve where I cannot find one. So, maybe they are typically there and I just haven't looked hard enough. If I have a check-valve where your diagram shows one, that would explain the hot/cold pressure differences.
2) City water connection is in a completely different place. Not sure it matters, but mine is T-d off the transom shower, so it is coming in on the other side of the accumulator.
This is perfect. It looks just like it should based on your earlier observations. I'm glad it's simple and not on the twilight zone end. You have confirmed that there is a check valve in the system, and that it is in the vicinity of @jssailem 's diagram indication. You can fix it by adding an expansion tank of adequate volume. If it were mine, I'd want to find the check valve. First, because I'm nerdy as hell, but second to make sure I didn't get the expansion tank connection wrong. I'd pull the fittings at the inlet to the water heater.
The reason your accumulator idea didn't help is due to the fact that it's likely outside of the check valve.
Agree that the TO 20 reading is probably hosed...
Good work!
As @jssailem states above, running it on the onboard pump will give you a dataset without city water pressure. Wouldn't take that long and might give some good additional info.
How is your pump controlled? The fact that it worked ok underway using engine heat is interesting. You were using on-board pump pressure, and the temperature may have been slightly different. Makes @jssailem 's test that much more enticing. It could be that your on board pump is producing a lower starting pressure than your regulated city water.
Very true. The fact that he said it only pukes 10oz of water, then stops, leads me to believe this is not the case, though. If it was boiling, it would relieve steam, which he would have noticed.
Since his system is so small, a few degrees difference, or a few ounces of relief make the difference between tripping the T&P or not. So, if his pump produces lower pressure than city, and his engine heater produces slightly cooler water, that easily explains why it doesn't trip underway.
Your point is well made. He should verify that the thermostats are controlling to set point before he calls it all done. These systems can fail catastrophically. I think that's why we are encouraging testing, in lieu of just parts swapping. He has a new T&P installed in the tank directly. That should protect him from a catastrophic failure. If he leaves the city water pressure on and the T&P trips, and his bilge pump goes bad, he may have a problem, though.
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