Using accumulator when pump has bypass valve

[Sam T]

My water pump (flojet R4405144A) recently developed a leak. It's been perfect for the 3 years I've had the boat and I imagine a long time before that too so decided to replace with the same model.

 

When it arrived it had a very specific warning on the box that is has a bypass valve and shouldn't be used with an accumulator tank.

 

My system does have an accumulator and i'd like to keep it if I can (no need for the pump to kick in if using water in the night etc).

 

Even if the pump works well without an accumulator, I struggle to see how having one would be an issue, but wanted to sense check this first.

 

I suspect my old pump had the bypass valve too and it isn't an issue(although this may have been added in the more recent versions of the same model). Before I installed it I wondered if anyone knew the logic or what kind of issues leaving the pressurised accumulator could cause theoretically?

Thanks in advance!

[pearley]

We have same pump but no accumulator. We have found that 3 1/2 years of liveaboard use before the diaphragm leaks is par for the course. I just put a note in the diary to replace on its 3rd birthday.

[Tony Brooks]

I had a phone chat with their technical department about this and the justification they gave made no scientific sense to me. In fact I think Jabsco make no such stipulation for their bypass pumps. I suspect a translation error from "there is no needs for an accumulator". The pump can have no idea if its flow is filling an accumulator or flowing form  tap.

[Sam T]

43 minutes ago, Tony Brooks said:

I had a phone chat with their technical department about this and the justification they gave made no scientific sense to me. In fact I think Jabsco make no such stipulation for their bypass pumps. I suspect a translation error from "there is no needs for an accumulator". The pump can have no idea if its flow is filling an accumulator or flowing form  tap.

Perfect, thank you! Exactly what I was hoping the answer would be. Thought that was the case but really reassuring to have it confirmed.

[dor]

Seems a bit pointless as most horizontal  calorifiers will have a bit of air in them so will act as an accumulator.

Edited October 26, 2020 by dor

[ditchcrawler]

1 hour ago, dor said:

Seems a bit pointless as most horizontal  calorifiers will have a bit of air in them so will act as an accumulator.

How does that help the cold water system?

[Tony Brooks]

31 minutes ago, ditchcrawler said:

How does that help the cold water system?

Only if the NRV is in a not normal locations.

[dor]

48 minutes ago, ditchcrawler said:

How does that help the cold water system?

A lot (most?) of calorifiers don’t have a NRV on the CW inlet.

[Tony Brooks]

23 minutes ago, dor said:

A lot (most?) of calorifiers don’t have a NRV on the CW inlet.

I would suggest that if there is no NRV as part of the calorifier assembly then one should be on the calorifier in let. If this is not done you can get hot/warm water out of the cold taps.  Especial if you have an expansion vessel. I would only deviate from this for a specific purpose.

[blackrose]

Put an isolator valve in the pipe to the accumulator. Simple to do and it gives you the option of "switching" the accumulator off or having it on to see which works better. The ability to isolate an accumulator is also useful when trying to identify if you have a leak in the system by listening to the pump activating.

Edited October 26, 2020 by blackrose