Water System

[Graysailing]

Hi
Wonder if anyone else has had this Problem, Just recently Launched and re filled my Water Tanks

The System Pressurises ok but when the Pump Turns off, there is a Loud Banging of Pipes form Under the Rear Cabin, on Investigation one of the Cold Water Pipe is Moving backward and Forwards, Made sure there are no Air Locks
A friend has suggested it may be to do with the  Accumulator

Any Help Appreciated

Last Chance 38

[Yngmar]

Sounds like you have a pressure wave (aka "water hammer"), which indeed does indicate that the accumulator isn't working. If it's the type with a membrane, it'll have a valve and you can pump it up to the nominal pressure with a bicycle pump, while the fresh water system is depressurized. That should sort it. If it's the type without a membrane, check if it has air at the top - if it doesn't, just empty it out and reconnect and it should start working.

[Salty]

My boat is a B36/2002, and it has a whitish translucent accumulator/pressure vessel located to port of the pump. This pressure vessel will unscrew (anti-clockwise when viewed from above) when the securing band around its middle has been released by undoing one screw at one or other end of the band. Being translucent you can with a suitable flashlight see the level of water within it. Note where the level is when the system is pressurised. If it’s at, or near to the top of the accumulator, then you will need to drain much of the water out. This is achieved by turning the pump off at the switch panel, then unscrewing the accumulator from its cap which is secured to the pipework just below the accumulator. Sometimes when unscrewed the accumulator tends to airlock such that no water, or very little comes out, but by shaking it up and down the water can be persuaded to run out. Let the level go down to a point somewhere around one third of its capacity, nearer the bottom than the top, then screw the accumulator back, clockwise, until it’s hand tight. Switch the pump back on, and the water level inside will rise as the air inside at the top gets compressed. With luck you will end up with a new level roughly one third of the way down from the top of the accumulator. Assuming you have been successful resecure the securing band and try it for a day or so until you are happy with the adjustment and then maybe mark the side of the accumulator so you know roughly where the level should be while the system is under pressure. Note that if you empty a tank and allow the pump to run on, that you will lose this setting and will then have to do it again. Yep, every time 🤬

[Graysailing]

Thanks for the Help

[dawntreader]

If you completely empty the accumulator bottle, once refitted, the pump will refill the bottle with water to a point that is equal to the inverse fraction of the pump working pressure + ambient air pressure (Boyle’s Law). Simply put it means that if your pump is rated at 3 bar you add 1 bar normal air pressure (3 + 1 = 4) then the bottle will be 3/4 water and 1/4 air. This is because water (for practical purposes) cannot be pressurized whilst the trapped air can. It should do this every time, on its own, from empty.

This explains how to charge your system but doesn't really cure your problem which is probably an air lock. Try turning on every tap then closing them down nearest to the pump first, furthest last, to try and clear it.