Pressure accumulation in the domestic water system issue

[mattonthesea]

I have a standard water pump with fitted switch, and a pressure accumulator, feeding the galley sink and heads basin. (There is also a T, before the pump, feeding a separate, filtered, hand pump but I don't think that this relevant.) The calorifier is a cuboid shape located in one of the saloon lockers. The pressure accumulator works well with the cold supply, the pump continuing on for a few seconds after tap is turned off and not always turning on when cold used. The variation in pressure is small over the cycles.

However, the pressure in hot taps (both) will vary a lot. The flow will drop to a trickle and maybe a drip before the pump cuts in again. I often turn the cold on momentarily to get the pump to operate again - out of frustration.

Obviously, there is something in the hot system that is back pressuring or accumulation pressure to fool the switch but I can't think what is causing this. If when the pump is operating the flow is full then there is no obstruction. If there were air in the system (calorifier) then would this not either work its way out or aid the flow of water when the pump is off?

I am planning to disconnect everything and inspect except the the calorifier was fitted in such a way that I cannot remove it without taking half the saloon and galley to pieces (I exaggerate). I should also add that the water temp is set to very hot and that I cannot get to the thermostat for the same reason! I will flush the system through and ensure no airlock after. Is there anything else I should be considering?

Thanks

Matt

 

[Wing Mark]

Is there a non return valve between the calorifier and the cold part of the system?
Could it be sticking?

Who makes cuboid shaped calorifiers, I might want one!

 

[mattonthesea]

Is there a non return valve between the calorifier and the cold part of the system?
Could it be sticking?

Who makes cuboid shaped calorifiers, I might want one!

No valve that I can see - but there is a chunk that I can't see :-(

I'll check the manufacturer next time. It is odd not having the boat a 10 min walk away!

 

[AndrewB]

If you have a non-return valve on the hot water supply, then an expansion tank should also be fitted, which should be obvious. As well as the non-return valve, there might be a sticky pressure reduction valve in the hot water circuit (fitted to stop drips from the calorifier pressure relief valve). These often cause trouble.

 

[SailingDog]

I have had a similar issue, finally came down to a filter between tank and pump being blocked with small stones and very fine particles, cleaned it out including gauze and water pressure back along with pump cycling normally.

Thinking of rigging up a portable filter on hose between shore tap and tank.