hot water tank

[Maine Sail]

Please remember that your T&P valve is temperature & pressure. The most likely cause fro a T&P to pop, on a boat, is the engine overheating the water and it opens on TEMPERATURE. This does not exclude the 120V aqua-stat from also failing and these too are replaceable.

Once a T&P valve opens they rarely if ever seal properly again regardless of any tank sediment. On a similar note the bladders in thermal expansion tanks for hydronic heating systems have become so crappy that they leak within a few years allowing for zero expansion when the boiler water is heated to 180F.. Once the expansion tanks bladder leaks the boilers relief valve pops and it too gets replaced otherwise it weeps. The T&P on a boiler is very similar to a water heater in its operation though with different limits. I just did this job on Saturday, again... Arghh...... The gaskets for T&P's sit in one place for so long that when they pop they get torn or chunks fall off them making them rarely if ever to seal properly again.

Solve the over-temp issue and the T&P will stop blowing. A pressure issue is highly unlikely unless you plumbed your boat direct to city water. Buying a new water heater because the T&P blew is like buying a new car because you got a flat tire...

 

[gettinthere]

My engine isn't overheating, thermostat never gets above about 180. I think 170-something is normal. The new relief valve was put in about 6 months ago. It is popping from dockside elec.
You think the engine heating caused the valve to pop and it's one and done? I have no idea how to determine overheating when the engine isn't overheating.

 

[Capt jgw]

I'd look at the electric thermostat. Easily replaceable from any hardware store. Of its stuck ON its sure to pop the T&P. That's what the T&P is for.

 

[Maine Sail]

My engine isn't overheating, thermostat never gets above about 180. I think 170-something is normal. The new relief valve was put in about 6 months ago. It is popping from dockside elec.
You think the engine heating caused the valve to pop and it's one and done? I have no idea how to determine overheating when the engine isn't overheating.

Remember most T&P's pop at 210F. This is pretty close to 180F... Open the tap and measure the water temp that comes out. On dock power it should be below 130F... On engine it should remain below 180 even after hours of motoring.

 

[jlp0217]

If you have, as Raritan recommends, a check valve on the cold water input, then as the water heats and expands will cause pressure to overcome the pressure valve. The more this happens the weaker the valve and it's seals get and the more they leak. If you want a check valve you need an expansion chamber between it and the heater.

 

[gettinthere]

Cold water to check valve and then to expansion tank and then to hot water tank inlet?
Hmmmm. My check valve is at the hot water tank inlet.

 

[scottdube]

Remember most T&P's pop at 210F. This is pretty close to 180F... Open the tap and measure the water temp that comes out. On dock power it should be below 130F... On engine it should remain below 180 even after hours of motoring.

Hi Maine,

This is similar to what is happening with my boat, it started off that the water heater was popping the limit switch. I thought it was the thermostat on the tank replaced that. Still was popping replaced limit switch. Still popping yesterday the T&P valve was relieving into the bilge. Temp gauge shows normal engine temp. Assuming the engine is heating up what would be first troubleshooting steps? Thermostat?

Thanks in advance!

 

[bawlmer]

Anyone with reports on Seaward tanks?[/QUOTE]

I have a 19 year old Seaward and it works just fine.