Accumulator question?

[Jeff James]

Hi all,

I have just replaced a leaking water pump on my motorhome with the exact replacement, a Shurflo Trail King 7L 30psi pump (12v). I also purchased a Shurflo accumulator, as I have experienced some water hammer on the tap furthest from the pump. The accumulators used to be sold pre-pressurised to 20 or 30psi, but now they are sold discharged and you need to pump them to the "Correct" pressure. However there is no pressure guide in the installation instructions, but there is a comment that a 45psi pump usually kicks in at about 30psi, so the accumulator should be set to 30psi. I am assuming that the accumulator pressure needs to be about 2/3rds of the pump operating pressure, so for my pump, I should set the accumulator to 20psi? This is also one of the 2 pressures that the accumulators used to be sold pre-pressurised to.
Would appreciate some advice/guidance, if my reasoning is about right, before installing the accumulator?
Thanks
Jeff

 

[funflair]

Hi Jeff

I have done a bit of reading as I am sure you have and I would draw the same conclusion as you

Martin

 

[Jeff James]

Thanks Martin,

I have e mailed Shurflo, over a week ago, to pose the question to them, but no response as yet.
Think I will set it at 20psi, unless somebody else has any other ideas.
Jeff

 

[pappajohn]

Thanks Martin,

I have e mailed Shurflo, over a week ago, to pose the question to them, but no response as yet.
Think I will set it at 20psi, unless somebody else has any other ideas.
Jeff

Then if it still knocks crank the pressure up a bit... If it STILL hammers crank it some more.
Keep adjusting up and down until it stops knocking.... Simple.

 

[Jeff James]

Many thanks pappajohn! I`ll crack on, get it fitted and adjust the pressure until right.

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[two]

Shurflo reckon that you don't need an accumulator, but I disagree. I simply pumped mine up until happy with the result. The pressure you pump it to will be the 'at rest' pressure, it will be increased once the pump has operated and stay at that pressure. Pumping too high will prevent any accumulation. A lower pressure will provide a larger range of 'tolerance'.

 

[pappajohn]

Many thanks pappajohn! I`ll crack on, get it fitted and adjust the pressure until right.

Now I don't know how to take that reply.

 

[Jeff James]

Cheers two, I get what you are saying, that the pressure shouldn`t be too high or you wont create an accumulation effect, so on you outfit, what psi does your pump operate at, and what psi do you have your accumulator set at? The Shurflo instructions that came with the new pump does state that if you have long pipe runs, and suffer from water hammer/cycling pump, then you should fit an accumulator?

 

[andy63]

hi Jeff, I have had accumulators in two vans now.. both with the fairly standard shurflo 20psi pump..
on one the pressure is set at about 12psi and the pump runs very well with very little cycling over a good range..that was on a self build..
I thought id try an accumulator on a coach built I got... its plumbed with the semi rigid pipe and wasn't that bad.. got some water hammer type noises at times .. after fitting the accumulator and trying all sorts of pressures I couldn't get the pump to behave .. it seemed to cycle more frequently and run on as if there was a leak before shutting down...
I gave up but intend going back to it again,,, maybe even removing the accumulator to see if it is better without..
Andy

 

[Jeff James]

Thanks for the info Andy, really useful. The hammer I have isn`t really bad, and the plumbing set up is exactly as it came out of the factory, but I am a bit of a perfectionist, hence why I bought the accumulator. But there again, over the years of owning motorhomes I know their construction is far from "Perfection", so I sometimes think, if it was good enough to role out of the factory, then so be it!
The number of man hours I have spent replacing wall timbers/wall boards, insulation, window seals etc, to cure leaks doesn`t bear thinking about, but that`s another story!

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[two]

Cheers two, I get what you are saying, that the pressure shouldn`t be too high or you wont create an accumulation effect, so on you outfit, what psi does your pump operate at, and what psi do you have your accumulator set at? The Shurflo instructions that came with the new pump does state that if you have long pipe runs, and suffer from water hammer/cycling pump, then you should fit an accumulator?

I got mine to reduce rapid cycling of the pump, not water hammer. Not sure what pressures but assume 20psi for the pump and less for the accumulator.

The idea was to take water from the accumulator before the pump cuts in to recover what has been taken and return to full pressure. You can flush the loo at night without the pump stirring.

I assume your hammer problem is on the cold side? The water boiler will act as an accumulator but is isolated from the cold side by a NRV.

 

[Jeff James]

Spot on two, hot is fine, just some hammer on the cold.

 

[Jeff James]

Accumulator fitted last weekend. Set pressure to 20psi, and has sorted the problem. Can now run the furthest tap at a trickle with no hammer, and pump kicking in every 5/10 seconds. Sorted!!

 

[Happy1]

Always fit them as manufacturers don’t the whale version is a tiny bit of kit that works great