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Accumulator and expansion tanks

I bought these as advised by the people I bought the calorifier off but the guy who put it in said I wouldn't need either of them so didn't plumb them in. I think I want to have them in really so am planning to install them myself. Am I right in thinking the accumulator needs to be after the pump as in water tank,pump,then accumulator.......and the the expansion tank at other end of boat : calorifier the expansion tank before pipe work?

Asked by: estelle lomax  | 10.24am, Saturday 14 October

WW says:

The accumulator tank, as you say, needs to go just after the water pump. The expansion tank should go on the hot water side after the calorifier (hot water tank)- usually just in the pipework after the hot water outlet from the tank- this will reduce stress on the tank and then the pressure relief valve is unlikely to have to operate...
Ensure that there is an non-return valve in the cold water feed to the calorifier- this will reduce the risk of warm water (and associated legionella risk) back-flowing along the cold water line, with the risk of drinking water contamination. The expansion vessel has to be downstream of this connection (which it is why it is placed in the hot water pipework) as if it is placed before the NRV it wouldn't function as an expansion vessel- but another pressure accumulator!

Mark Langley  | 11.02AM, Saturday 14 October

Also I should add the most common reason for calorifier failure is the stress caused by the expansion of water as its heated. If the pressure becomes too high then the pressure relieved valve will vent excess water, but by that point a large amount of mechanical stress has been placed in the cylinder. Using an expansion vessel on the hot water side will prolong the life of a calorifier substantially- and usually avoid the pressure relief valve having to operate at all.
It is worrying that some people who install water systems on boats give wrong advice!

Mark Langley  | 11.05AM, Saturday 14 October

Readers say:

Am going to have a go today 😊

estelle lomax  | 10.59AM, Sunday 15 October

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