Seaward hot water tank

[Bob 04 H260]

The pressure relief valve on my hot water tank has a drip whenever the tank heater is turned on. Can it be replaced with one from Homedepot or do I need to order it from Defender ?

Thanks, Bob

 

[Chris Patterson]

Home Depot. There's no difference.

 

[Maine Sail]

Any plumbing supply house will have them. Be sure to write down the model and at least the temp and pressure rating. The temp side should be 210F. Some marine heaters often use lower T&P pressure rating than some home water heaters... Often they will be 75PSI or 100PSI as opposed to a 150PSI which is designed for a 300PSI ASME rated tank..

IMHO a 75 PSI / 210F T&P is the best choice on most boats otherwise you'll just blow hoses instead...

 

[Bob 04 H260]

Thanks, that makes sense, I'll look for a 75 psi rated valve. The valve on there now is 150 psi, 210*.

Bob

 

[wflowe2]

I put a new heating element in mine using one I got at Home Depot.

 

[Ralph Johnstone]

The pressure relief valve on my hot water tank has a drip whenever the tank heater is turned on. ?

From that, can I conclude that it doesn't drip if the heater isn't turned on ?

I had a similar problem after I first bought our boat in that the relief valve did leak when heat was first applied to the tank (either electric or engine hot water). This turned out to be due to the thermal expansion of the cold water in the tank exceeding the relief valve setting. The leakage disappeared after the tank was hot and any water (hot or cold) was drawn from the system. The problem disappeared after an expansion tank was installed.

Before installing a new relief valve, see if the leakage will stop after you draw some water from the system. No luck ? ................. try fully lifting the handle on the valve and snapping it shut to see if this will dislodge any dirt on the valve seat or disk. Still no luck ? ............ see the above poster's suggestions.

 

[Bob 04 H260]

From that, can I conclude that it doesn't drip if the heater isn't turned on ?

I had a similar problem after I first bought our boat in that the relief valve did leak when heat was first applied to the tank (either electric or engine hot water). This turned out to be due to the thermal expansion of the cold water in the tank exceeding the relief valve setting. The leakage disappeared after the tank was hot and any water (hot or cold) was drawn from the system. The problem disappeared after an expansion tank was installed.

Before installing a new relief valve, see if the leakage will stop after you draw some water from the system. No luck ? ................. try fully lifting the handle on the valve and snapping it shut to see if this will dislodge any dirt on the valve seat or disk. Still no luck ? ............ see the above poster's suggestions.

Ralph, as usual all good advice. It has been dripping for a week since recommisioned the boat and moved aboard. I first tried to open it and flush it out but no joy there. I think the solution is going to be a new one from HD.

I have a brand new expansion tank ready for installation. It came with the boat when we bought it. It's on my todo list but it never got to the top. I noticed the drip because I could hear the pump give two strokes about every 2 hours at night. That was how I realized I had a slight leak. I'm thinking with an expansion tank the leak might not have been noticed until I found something wet that should be dry !

Thanks again for the tips, all good stuff !
Bob

 

[Lee Hadjiosif]

The pressure relief valve on my hot water tank has a drip whenever the tank heater is turned on. Can it be replaced with one from Homedepot or do I need to order it from Defender ?

Thanks, Bob

Don't bother replacing it..it will drip again due to over-pressure. The only way to fix it is to install an expansion tank. If you already have an expansion tank with the proper air pressure in it, then you should replace the PRV. Got this straight from Seaward.
Lee

 

[Bob 04 H260]

Don't bother replacing it..it will drip again due to over-pressure. The only way to fix it is to install an expansion tank. If you already have an expansion tank with the proper air pressure in it, then you should replace the PRV. Got this straight from Seaward.
Lee

Thanks Lee, that makes sense and agrees with Ralph's experience too. Guess I'll add that pressure tank while I'm at it.

Bob

 

[Chris Patterson]

How is an expansion tank going to reduce the pressure?

 

[Bob 04 H260]

I think the idea is, if the hot water circuit is only water and it is heated so it expands the pressure generated will exceed the the pressure rating of the relief valve. If there is an expansion tank in the water circuit the air in the tank will be compressed the pressure will go up but not go high enough to open the pressure relief valve. The air can be compressed but the water can not.

Bob

 

[Davidasailor26]

I noticed the drip because I could hear the pump give two strokes about every 2 hours at night. That was how I realized I had a slight leak. I'm thinking with an expansion tank the leak might not have been noticed until I found something wet that should be dry ! Thanks again for the tips, all good stuff ! Bob

If the valve is leaking at such a low pressure that the drip is allowing the cold water pump to cycle, then an expansion tank won't solve the drip. The expansion tank will keep the pressure stable longer, but the pump will keep the pressure high enough that the valve will keep dripping. The pump pressure should be much lower than the relief pressure of the valve, so your report suggests that it's definitely time for a new valve. Of course it's also possible that you have a second leak elsewhere in the plumbing causing the pump cycling too.