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Should I reduce my calorier pressure when I leave the boat?

When I leave my boat I switch off the battery isolator. This, among other things, turns off the water pump.
But the calorifier system remains pressurised, so to reassure myself I run the hot tap to release the pint or two of water that the pressure forces out.
My question: Does this make any difference? And does the pressure remaining make the water less or more likely to freeze were an unexpected frost to strike?

Asked by: Andrew Denny  | 9.47am, Wednesday 2 November

WW says:

Relieving the pressure will reduce unnecessary strain on the calorifier. As to whether water under pressure will freeze more or less readily I am not sure, however the potential frost damage may be slightly higher under pressure. Water is in fact not compressible, it is the air dissolved in the water that compresses. It has been experimentally proved that hot water will freeze faster than cold due to higher molecular activity.

Rupert Smedley  | 2.23PM, Wednesday 2 November

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