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pezvela's avatar
pezvela
Explorer
Jun 05, 2013

RV-type water heater modification for my boat?????

I purchased a Seaward S-600 water heater and I am having a dickens of a time getting it to fit into the space of the old one on my boat. This is one intended for use in a boat.

It appears to be a conventional RV water heater tank. Six gallons, pressure and temperature relief valve with the same values, same ID on the hot and cold fittings. It uses coolant from the engine to heat the water.

My main problem is that the P/T relief valve sticks out so far that I am hitting a bulkhead. BUT IF I COULD SWAP THE P/T RELIEF VALVE WITH THE SACRIFICIAL ANODE PORT, I COULD MAKE IT FIT. They are both the same size.

Is there anything about the sacrificial anode port that would make this unfeasible/unsafe?

Just thought I'd throw this out there as I am working on it right now and the mfgr is closed for the evening. But I will be calling to make sure.

5 Replies

  • Reelescape1 wrote:
    If you have to replace it why not an on-demand unit?


    Because to my knowledge, on demand doesn't work when trying to make hot water from engine heat via heat exchange.
  • Just got a reply from Seaward tech dept. They say it is no problem swapping them, although the anode port is slightly closer to the heat exchanger and may be triggered slightly earlier.
  • Just curious - what would be the reason the P/T valve needs to be high in the tank? The pressure is constant from top to bottom, and I would expect with normal mixing during heating that the temp would be fairly constant as well.

    The P/T valve is below the air pocket anyway, if any exists. This is why they seep during continued usage - the air pocket is eventually absorbed.

    My initial question about this swap - do both ports have the same thread size?
  • Relief valve needs to be on the top of the tank, either via the side face or the very top, if both the anode and the relief are on the very top of the tank, swapping them should make no difference.

    If the relief is on the top and the anode lower down, then swapping is not possible.