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Old 02-16-2020, 02:43 PM   #1
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Water Heater Pressure/Temp Relief Valve Discharge

Recently our three year old Seaward Model 2050 240v water heater started having releases from pressure relief valve. Replaced valve, still discharging. Made sure water system accumulator tank had a 30psi charge (the cut in point of our water pump as accumulator instructions indicate) to provide the "cushion" needed on the cold water side. Still discharging. This one is now getting past my pay grade. Any suggestions? Thanks.
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Old 02-16-2020, 04:18 PM   #2
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I am not much of a plumber but maybe the thermostat has gone bad and is overheating the water. That would cause the pressure to go up and the relief valve to vent. Check the temperature of the water coming out of the heater and see if it is too hot.
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Old 02-16-2020, 04:21 PM   #3
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Is the water heater have an engine heat coil? Maybe the engine is running hotter than before?
Also the T&P valve is easy to replace with decent access, a pipe wrench and pipe dope.
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Old 02-16-2020, 04:52 PM   #4
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Is the water heater have an engine heat coil? Maybe the engine is running hotter than before?
Also the T&P valve is easy to replace with decent access, a pipe wrench and pipe dope.
I have heard of this happening many times... I have also heard of hot water heaters making the engine run hotter. Sooooo, the obvious trouble shooting is to isolate the tank from the main engine after you make sure the tank's thermostat is operating properly.

On my AT, I have had isolation, in and out, valves installed. Plus it will make it easier to change the HW tank.
Also, when underway it is not necessary to have the electric side of the water heater turned on.
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Old 02-16-2020, 04:59 PM   #5
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P/T Relief valves have a finite lifespan. Replace it.

Be careful though. Things have changed over the years and it's entirely possibly that the new one will be set for a lower temperature. Especially if you use an engine coolant loop in the tank, it may be set too low.
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Old 02-16-2020, 05:26 PM   #6
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P/T Relief valves have a finite lifespan. Replace it.

Be careful though. Things have changed over the years and it's entirely possibly that the new one will be set for a lower temperature. Especially if you use an engine coolant loop in the tank, it may be set too low.
We’ve replaced ours twice and the replacement fixed the problem. Watts makes most of the pr valves but they make many models. I’d check with Seward for the right one.
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Old 02-16-2020, 07:01 PM   #7
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Thanks for all the suggestions.
-I have already replaced the valve with the specified valve.
-We do not have an engine heating loop, electric only model.
-Water is normal 140 degrees (thermostat spec) so thermostat does not seem to be the issue.
Still searching for the solution....
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Old 02-16-2020, 07:28 PM   #8
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Thanks for all the suggestions.
-I have already replaced the valve with the specified valve.
-We do not have an engine heating loop, electric only model.
-Water is normal 140 degrees (thermostat spec) so thermostat does not seem to be the issue.
Still searching for the solution....
Turn it down to 120 and see makes a difference. The reason the house temp is so high is, it has to be hot at the furthest faucet. On the boat, the pipe to the most distance faucet is not that far.
One additional question, do you have a separate expansion tank for the HW heater? When I replaced my HW heater at home, the code required a separate copper expansion tank on the top of HW tank. That may be an option too.
I would start by turning the thermostat down first.
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Old 02-16-2020, 07:42 PM   #9
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Turn it down to 120 and see makes a difference. The reason the house temp is so high is, it has to be hot at the furthest faucet. On the boat, the pipe to the most distance faucet is not that far.
One additional question, do you have a separate expansion tank for the HW heater? When I replaced my HW heater at home, the code required a separate copper expansion tank on the top of HW tank. That may be an option too.
I would start by turning the thermostat down first.
Thanks for these additional suggestions.
The thermostat is set to 140 by the factory. Non adjustable (Seaward model H2050EW). I do not have a hot water side accumulator. Nothing in the manuals suggest a hot water side accumulator. The unit worked fine for 3 plus years. I am going to try customer service at Seaward tomorrow....
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Old 02-16-2020, 07:48 PM   #10
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Thanks for these additional suggestions.
The thermostat is set to 140 by the factory. Non adjustable (Seaward model H2050EW). I do not have a hot water side accumulator. Nothing in the manuals suggest a hot water side accumulator. The unit worked fine for 3 plus years. I am going to try customer service at Seaward tomorrow....
LOL should have done that first.
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Old 02-16-2020, 08:03 PM   #11
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Is the weeping or is it popping?

Do you have a tempering valve upstream of where you are measuring the hot water temperature?

Do you have a check valve on the cold water inlet?

Is it happening when a tap is turned on or off?
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Old 02-17-2020, 10:33 AM   #12
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So, additional checking this morning. I first looked at the specs on the tag of the new relief valve I had installed. They must have sent the wrong one even though I ordered by manufacturer part number! Only 100psi valve and specs say min 127.5 to max 150 psi. Reordered and will install correct valve and report back....fingers crossed but seems logical.
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Old 02-18-2020, 03:33 AM   #13
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So, additional checking this morning. I first looked at the specs on the tag of the new relief valve I had installed. They must have sent the wrong one even though I ordered by manufacturer part number! Only 100psi valve and specs say min 127.5 to max 150 psi. Reordered and will install correct valve and report back....fingers crossed but seems logical.


Those pressures seem high, dose your water cylinder run at over 100 psi during normal operation?.
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Old 02-18-2020, 04:03 AM   #14
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Just a footnote, your accumulalor pressure should be set at 2psi BELOW the cut-in pressure of your pump. At least that is what every reference I have read says. I'm surprised your instructions said differently.
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Recently our three year old Seaward Model 2050 240v water heater started having releases from pressure relief valve. Replaced valve, still discharging. Made sure water system accumulator tank had a 30psi charge (the cut in point of our water pump as accumulator instructions indicate) to provide the "cushion" needed on the cold water side. Still discharging. This one is now getting past my pay grade. Any suggestions? Thanks.
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Old 02-21-2020, 12:24 PM   #15
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Closing out this thread....new properly spec'd pressure relief valve solved the issue. Thanks to all for the inputs.
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Old 02-22-2020, 02:12 AM   #16
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I am having the same leak/weep problem with the same new unit. Based on your experience I checked the tag on my valve. Yup, it's a 100psi valve. I already called the factory once and was told that new valves sometimes take a while to seat and finally seal. Seems apparent that they produced a run of heaters with incorrect valves. I'll be calling on Monday to get a 127.5psi valve sent.
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Closing out this thread....new properly spec'd pressure relief valve solved the issue. Thanks to all for the inputs.
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Old 02-22-2020, 06:19 AM   #17
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Now the question is why your water pressure is exceeding 100 psi? That's super high.

I suspect you have a check valve in the flow path of the cold water feeding the HW tank such that when all the hot water taps are turned off, the HW has no expansion path back to the accumulator. My Grand Banks had a similar plumbing error.
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Old 02-22-2020, 08:15 AM   #18
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Now the question is why your water pressure is exceeding 100 psi? That's super high.

I suspect you have a check valve in the flow path of the cold water feeding the HW tank such that when all the hot water taps are turned off, the HW has no expansion path back to the accumulator. My Grand Banks had a similar plumbing error.
The new check valve with the originally specified 127.5 to 150 psi works fine. Talked to Seaward and they were not surprised the 100 psi valve leaked so apparently 100 plus psi is not abnormal for the heating cycle. All is well now (as it was for 4 years prior). Just a worn out valve….
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Old 02-22-2020, 08:49 AM   #19
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Now the question is why your water pressure is exceeding 100 psi? That's super high.

I suspect you have a check valve in the flow path of the cold water feeding the HW tank such that when all the hot water taps are turned off, the HW has no expansion path back to the accumulator. My Grand Banks had a similar plumbing error.
Your suspicion is correct. However, I did not use a check valve on the original install but the pressure valve leaked both before and after the installation of the check valve. An expansion tank is likely to solve the problem but no way am I going to bother with more plumbing and additional space consumption. Since Seaward specs a 127.5 psi valve for my unit, I will use one and solve the problem. It would seem apparent that Seaward does not have a problem with pressures approaching 100 psi although that does seem very high. Oddly, the hot water outlet pressure in the galley is rather anemic until the water pump (Grundfos MQ3-45, 120VAC) kicks in. Cold water pressure there is just fine. The Grundfos provides gobs of volume and steady pressure. Hot water pressure in the two heads and in the shower is strong so the galley pressure issue is likely something that can be solved.

BTW, your old Manson Supreme anchor still sits proudly on my bow. Never a failure so far.
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Old 02-23-2020, 08:52 PM   #20
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Well, it's never over till it's over. I actually have another problem now. After a couple days went into ER and had water. No leaking relief valve so pulled cabinet off heater and pulled back sopping wet insulation blanket. Yep, a weep at one of the welds in the top of the tank. Leaked with cold water only in the tank (somewhere between 30 and 55 psi, the pressures of our fresh water pump operation.
Twisted Tree, you are also correct there is a check valve in the cold water supply line so that does cut off the ability of the fresh cold water accumulator tank to absorb the water pressure from heating. I will be removing it before I install the new heater that is on order. Even though the Seward tank is a 150 psi rated tank, there is no reason to "test" the new tank constantly without a relief path. Hopefully this new heater lasts longer than the last one...
Thanks to all for all the suggestions along the way to solving this.
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