Accumulator pressure

[Ian_Edwards]

I'm about to install a new fresh water pump.
It starts pumping at less than 30psi and turns off at 40psi.
The accumulator, and I'm assume that's what it is, because it's fitted directly after the pump, needs to have the pressure in the bladder set. the label say that it is set at 40psi.
That seem to high to me, because with a max pressure of 40psi, the bladder isn't going to move.
Setting it to 35psi, seems superficially, to be the right thing to do, then as soon as the pump starts, and the pressure increase above 35psi, the air will start to compress and store water under pressure.
I'm I on the right track?

 

[vyv_cox]

I have written this several times previously, must put it on the website!

With water in the tank and the accumulator in line, turn on a tap. Note that the pump runs constantly. Begin to pump air into the accumulator. The water pump will run more intermittently, remaining off for longer periods as more air is pumped in. Eventually this will reverse and the 'off' periods will reduce in time as air pressure exceeds water pump pressure. Let a little air out until the maximum 'off' is regained. Job done.

 

[Boater Sam]

Or.
Switch off the pump, open a tap.
Pump up the accumulator to over the cut out pressure of the pump, 45 psi will do.
Close the tap.
Switch on the pump, let it run till it stops.
Very slowly let the air pressure down until the pump just restarts.
Job done.

 

[VicS]

I'm about to install a new fresh water pump.
It starts pumping at less than 35psi and turns off at 40psi.
The accumulator, and I'm assume that's what it is, because it's fitted directly after the pump, needs to have the pressure in the bladder set. the label say that it is set at 40psi.
That seem to high to me, because with a max pressure of 40psi, the bladder isn't going to move.
Setting it to 35psi, seems superficially, to be the right thing to do, then as soon as the pump starts, and the pressure increase above 35psi, the air will start to compress and store water under pressure.
I'm I on the right track?

A good practical method is as Vyv describes

If you want to set the "recommended" pressure by measurement it is 2-3 psi below the pump cut in pressure

A good explanation of accumulator and expansion tank theory, sizing, installation and pressure settings can be found at
https://www.jabscoshop.com/files/Accumulator and Expansion Tank Instructions ZPWL4 doc595.pdf

.

 

[VicS]

If you like videos here's one from Jabsco Technical Support

 

[superheat6k]

Can I suggest when fitting a new pump you check what the original pressure the pump being replaced was set at.

I fitted a 3 bar pump on my last boat and blew out the base of the water calorifier, so it formed an external dome. It worked for a while but eventually split along a seam. The Safety valve also had to be replaced to cope with the increased pressure.

 

[Ian_Edwards]

The old pump was 35psi switch off.
I guess that 40psi wasn't enough to cause a serious issue.
I've tried a old 25psi pump which I had in the garage, and that's not enough to push the water the carbon filter I use, and give useful flow.

 

[VicS]

A good explanation of accumulator and expansion tank theory, sizing, installation and pressure settings can be found at
https://www.jabscoshop.com/files/Accumulator and Expansion Tank Instructions ZPWL4 doc595.pdf

Whoops wrong link. Should have been

https://www.jabscoshop.com/files/Accumulator and Expansion Tank Instructions ZPWL4 doc595.pdf

.