Hot water coming out of cold taps after running engine (non-return valve?)

[B40-Lefkas]

When using the engine, we are getting scolding hot water when running either the hot or the cold water taps. If we run the cold for a minute or two then it clears through the pipe and come out cold. It seems there might be a non-return valve in the calorifier that is broken and allowing hot water to exapnd/flow back into the cold water intake.

Has anyone experienced this before? Do you know if it's something in the calorifier that is replaceable? What do you think about just adding a non-return valve inline in the cold water supply?

Thanks for your help.

Chris

[Salty]

I think before we can give any advice, or make suggestions, that you need to do a little investigation of the situation.
You say that the cold water taps run hot, but then cools off after a minute or two. This suggests to me that you have a leak somewhere, or that the cool water that enters your hot water system as you draw off hot water is expanding as it heats up and is able to travel back towards the the pump and your cold water storage tank. So lift the cushions above where your fresh water pump is located, and after your engine has been running for a while but before you draw off any water, feel the pipes and determine how far towards the cold water storage tank the hot water in your cold pipes has travelled. Determine whether the hot water has reached your pressure tank, or has it gone further towards the pump, or possibly on beyond the pump almost to your cold water storage tank, and then let us know. While you are checking things in that area, look for any water leaks and advise us if water is present in areas that should normally be dry.

[MarkTheBike]

Does the cold pipe run above the hot pipe with the hot pipe heating the cold pipe? I appreciate 'scalding' hot water indicates something a bit more direct than that but it's just a thought...

[Earlvis]

I assume you fixed this....for the other people that are looking and have a similar problem...this is caused by a faulty one way valve between the inlet and outlet of the calorifier. The one way valve looks just like a short piece of water pipe...could be white or copper coloured....usually has an arrow on it.

Make a note of it's orientation..turn off the water pump....Disconnect it from the whale couplings at both ends...and inside is a small plastic "slug"....there should be an O ring on one end....if yours is not working it's because the O ring is missing....put a new O ring on and re-assemble.

[B40-Lefkas]

Many thanks for the responses, I feel sure it is the non-return valve. I will look at it when I am on the boat next (it's in Greece) and will update this thread.