do i need an accumulator in the fresh water supply ?

The time an accumulator is useful is when you have more than one person on the boat and you have the potential for a hot shower that could vary if the pressure changes.

If you are alone or you can train the other occupants not to open a tap while you are showering no accumulator is required.
 
We have a similar pressure pump, a Jabsco IIRC, functions very well with no accumulator. If you need to then it’s dead easy to add one to the system later
 
We had an accumulator that was old and sprung a leak so I bypassed it. I notice the pressure pump comes on now after maybe 20 seconds running instead of over a minute but that's a very minor annoyance. I got a new accumulator fitted over the winter but it took me months to notice that the technician had left it bypassed.
 
Personally I like using an accumulator purely so you don't hear the pump going every time you run the tap just for a glass of water.
 
northcave said:
Personally I like using an accumulator purely so you don't hear the pump going every time you run the tap just for a glass of water.
Click to expand...

That depends on the size and complexity of your water system. With plastic pipes, three water tanks, hot water system and two heads/showers and an aft cockpit shower there is a lot of expansion in the system so bypassing the accumulator has made little practical difference (30 seconds silent flow rather than 2 minutes). Try bypassing yours as an experiment.
 
If your system works happily without an accumulator, and the pump doesn't come on very quckly when you turn on a tap, then you have an air space somewhere (calorifier?) which is doing the job of an accumulator. Or maybe a lot of flexible hoses?

On some systems, the accumulator is what allows the water in the calorifier to expand as it heats, without peeing out through the pressure relief valve.
 
lw395 said:
If your system works happily without an accumulator, and the pump doesn't come on very quckly when you turn on a tap, then you have an air space somewhere (calorifier?) which is doing the job of an accumulator. Or maybe a lot of flexible hoses?

On some systems, the accumulator is what allows the water in the calorifier to expand as it heats, without peeing out through the pressure relief valve.
Click to expand...

I think it's a lot of semi-flexible hoses - even the rigid plastic pipes will expand slightly with pressure - you don't need air in the picture.
 
RupertW said:
I think it's a lot of semi-flexible hoses - even the rigid plastic pipes will expand slightly with pressure - you don't need air in the picture.
Click to expand...
Boat domestic water systems are pressurised to what? less than 2 bar springs to mind, but I stand to be corrected.
At home I have a 35m garden hose, which when I turn it off at the wall, then release the pressure at the nozzle, I don't get much water from.
And that's cheap garden hose. Going down to zero pressure
I don't think the flexibility of boat plumbing is generally going to give you a pint of water between the pressures where the pump cuts in and the pump cutting out.
That's why many/most systems have an accumulator. If you don't need one though, you don't need one.

The other irritation of not having an accumulator can be the pump cycling at 4 AM as the calorifier cools enough to trip the switch.

My old boat went happily with a duff accumulator and air in the calorifier until we put it on its ear in the RTIR, then we started having water coming out of the PRV and the pump short-cycling.
 
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