Seaward S-600 Water Heater Popping Pressure Relief Valve

[Rortega46]

My Seaward S-600 hot water heater is popping the pressure relief valve.  Some prior posts suggest changing the thermostat and pressure relief valve.  I have the parts and am now ready to install.  It looks like the water heater will need to be removed to install them.  Is this correct? I'd appreciate suggested detail instructions from anyone who has changed water heater parts.  Do I need to remove it?  What about the water lines?  Any tricks or things to keep in mind?

[Ken Juul]

Not sure about the MK2, on the MK1 they both can be changed in place.  Turn the water pump off, turn off the water heater electrical circuit, open the drain, disconnect the wires and unscrew.  There are wrenches/sockets availabe at Home Depot/Ace if you cant get a standard wrench/socket on it.  Disconnect the pressure relief drain hose if install and unscrew.

[KWKloeber]

When one changes out multiple things you don't know the underlying culprit.   If the water temp is ok why the thermostat?  Most likely its just a bad valve.   Maybe its not important to isolate the root cause but not knowing would make me crazy 

[Jim Hardesty]

I changed the pressure relief valve on my MKll with the tank in place.  Have not changed the thermostat in place.  If it were me I'd just change the relief valve and see.  IMHO the less plumbing work the better.  FWIW  I think my relief valve failed due to the PO opening the valve when he winterized.  Two seasons ago had to replace my water heater.  It was a PITA.  Got the old tank out with quite a bit of effort.  Could not get the replacement in with the batteries in place.  So had to remove the batteries and the battery tray.  PITA

[Ron Hill]

Randy : I'd try changing the pressure relief valve. 

[Footloose]

FWIW-I had the pressure relief valve go bad on my furnace this year.  It just unscrews.  As others have said, I would replace just the valve and leave the thermostat alone.

[Stu Jackson]

From earlier posts about this issue:

If your PRV is popping, then your water could be too hot from electric heating. There is NO need to keep the electric working all the time; heat the water, turn the power off; it only takes about 15-20 minutes to heat the water. PRVs have been known to fail when "exercised," which is why there is no reason to do so; crud gets in and keeps it open. If you have crud, it means your heater could be failing; 15 years is usually at the end of its useful service life.

[Rortega46]

Thanks everyone for your replies and suggestions.  This weekend I will try changing just the thermostat.  I think it will work in there without removing the entire water heater, and it sounds like a good idea to isolate the problem.  To change the thermostat you remove a cover and then some sort of secondary cover which I can't figure out how to remove without taking the whole *!***! water heater out.  Hopefully changing the PRV will solve the problem and there will be no need to change the thermostat.  Thanks again to everyone!

[Stu Jackson]

Could I be the only one who doesn't understand your post?

Are you changing the thermostat (which we recommended as unnecessary) or the PRV?

[Rortega46]

I am changing the PRV.  The prior post was a typo.

[Ron Hill]

Randy : The PRV change out should take care of the engine heated water. 
I found that if a PRV is ever manually opened (even to check it) that crud/sediment tends to get caught in the valve gasket and it will always tend to seep a bit.

However, if your shore power is overheating the water and causing the PRV to open - I wrote a Mainsheet tech note article a couple of years ago on changing that AC thermostat out.  Not that difficult !!

A few thoughts

[Stu Jackson]

However, if your shore power is overheating the water and causing the PRV to open - I wrote a Mainsheet tech note article a couple of years ago on changing that AC thermostat out. 

Not that difficult !!

And not at all necessary.  Read my earlier post.  Just don't keep the power ON all the time.

There:  just saved you some time and $$.

Betcha have better things to do on your boat.

Good luck.

[Rortega46]

I will try changing the PRV this weekend and will let you know how it goes.   I look forward to getting this one behind me and moving on to the next project.

[Rortega46]

Ron

Thanks for letting me know there's a Mainsheet article on changing the AC thermostat.  I am hoping it's not necessary. 

[J_Sail]

And not at all necessary.  Read my earlier post.  Just don't keep the power ON all the time.

There:  just saved you some time and $$.

Betcha have better things to do on your boat.

I disagree with Stu. The thermostat is an important safety item and if it is not functioning MUST be replaced. It is not acceptable/responsible safe practice to operate a water heater with a malfunctioning thermostat and simply plan on remembering to turn of the breaker after 15 minutes. If one forgets there is risk of scalding, failure of plumbing components due to excessive heat, and in the extreme case a fire should the water boil and get released thru the PRV, leaving the heating element energized in a dry environment. AND, if the PRV was stuck (not applicable in this case where it is already leaking, but could be true otherwise) the whole thing could explode.  That said I concur that it is not the most likely cause of your problem, so is probably a moot point to you.