Fresh water pump pulsing

[dawntreader]

My 2005 model Shurflo fresh water pump gave up recently (ate the bearing) and I replaced it with a Jabsco 2.9 GPM type 31395 pump on a like-for-like basis. Although the Jabsco model claims 'smooth flow and hassle-free' operation it pulses water at the far end of the distribution system (in the heads). Is there anything I could do to reduce/stop this?

[Yngmar]

You can add a small (caravan/boat sized) pressure accumulator between the pump and the rest of the system. It'll store pressure by way of compressing an air bladder and keep the pressure more balanced and the pump working less too.

I've split the topic, as your question had nothing to do with the other thread

[dawntreader]

Thanks for the info Yngmar but I've already got a pressure accumulator in the system. I will check to make sure it's working ok     but this was a 'swap out' and the pressure/flow was fine before. I am beginning to suspect that despite the increased rating - was 2.8gpm now 2.9gpm - the pump may not be up to the job 

[ITIL MAN]

This may not be the same issue but when my pump started to leak (PAR-MAX 2.9) I bought a new one from Force 4 and i noticed that the shower did not seems as powerful and it also started to pulse the water more frequently.  I checked it again aganist the old one and noticed it was not 40 PSI but lower, despite all the other flow and ratings were the same.  It looked identical but when checked with force 4 they did have two types.  Replaced it witht he 40PSI and all is well.

The only other time i have heard the water pulse is if the transom shower was leaking slightly or not turned off properly.

Sorry if this doesnt help you.

[dawntreader]

OK, done some more research and it appears my problem is that the pressure accumulator is full of water whereas information I have read suggests that it should only be 2/3rds full to stop it pulsing. I cannot find any installation instructions for the accumulator (model is "Comet Pressure Equalizer") so I would appreciate some help on how to set this up 

I ought to add that I didn't fill it with water and seem to remember that there was an 'air pocket' in the bottle with the old pump.

[Yngmar]

It's supposed to be full of air when the system is depressurized, then fill with water from the bottom, so the air at the top is compressed and starts acting as a spring on the water below.

Larger ones have a membrane to keep water and air separate. The Comet type does not, so when the boat heels the air can sometimes escape into the outlet. Ours needs "resetting" every few weeks or months.

To reset it, I switch off the freshwater pump, depressurize the system by opening a tap until no more water runs (and leaving it open!), then slowly unscrewing the cylinder from its fitting until it's nearly empty. Air will bubble in while the water drains out through the outlet, at least on our boat, as the cylinder is above the tap. When enough air is back in there, close everything, turn the pump back on and it should work now.

[dawntreader]

Thanks Yngmar, that appears to have sorted it out. It was made difficult due to the following: the installation is under a shelf and under a bunk (working upside down in the dark); the bottle is below the tap (but didn't drain the system once removed); the bottle and attached pipework were fitted too high to the underside of the shelf so the clearance when trying to remove the bottle was very small. Anyway, emptied it completely and then ran the taps to clear any air in the system. Not pulsing now  I have put a pencil mark on the bottle at the current water/air interface to monitor change.
Thanks, Jim

[PEA-JAY]

Easy way to drain accumulator; switch off pressure pump, open a tap to release pressure, place a suitable recipient under an elbow which is beneath the accumulator and release pipe from the elbow. Gently squeeze the accumulator a number of times until it’s empty and re-seal system.

[dawntreader]

Thanks pea-jay but just unscrewing the bottle did the trick even though it was a bit fiddly. What I do not understand is how the air got out in the first place. The bottle is inverted so 'heeling' would not affect it. To rub it in, I am still trying to get a small bubble out of my fuel filter - it's not causing any problems but it just won't go away 

[Spirit of Mary]

Water under pressure can contain more air in solution than water under atmospheric pressure (water under vacuum will release air).This means the water very very slowly will absorb the air in the accumulator. It helps when the water tank is used to complete empty. The pump then will pump air in the accululator and after the tank is filled with water again, the air in the accumulator will be compressed to the normal level. If you do so you never need to manual fill the accumulator wth air.

[PEA-JAY]

Well done Spirit of Mary you’re correct. No way can you get air normally out of the bottle unless you’re in the habit of rolling the boat over once a year!
 
Please  allow me to pass another useful tip once we’re on the subject of a fresh water system problem.
I was told by a knowledgeable friend, whenever possible, to cycle the hot water from the calorifier, as we tend to prefer using cold water (it takes a while for hot to arrive anyway). The reason being that the stainless steel calorifier will oxidise with stagnant water and consequently weld seams will rust and leak.

[Salty]

Please  allow me to pass another useful tip once we’re on the subject of a fresh water system problem.
I was told by a knowledgeable friend, whenever possible, to cycle the hot water from the calorifier, as we tend to prefer using cold water (it takes a while for hot to arrive anyway). The reason being that the stainless steel calorifier will oxidise with stagnant water and consequently weld seams will rust and leak.

That’s a really good point Pea-Jay, too often stainless steel seems to be considered as some kind of wonder material, but it’s Achilles heel is being immersed in stagnant water for long periods of time and where the consequent lack of oxygen results in accelerated rates of corrosion.

[Kibo]

Anyone know if there is an accumulator fitted to a 2014 Vision 46?

I cant seem to find one despite tracing all the fresh water lines so I'm pretty sure I don't have one. Are the ones you guys talked about an after market fit?

My pump doesn't pulse under full load but does a little under lower load when the tap isn't fully turned on so I am thinking I could fit one.

Any tips on where best to fit it? eg does it need to be higher than the pump itself? 

Thanks

[PEA-JAY]

I cannot reply to your first question. We’re talking about Bavaria standard fit accumulator unit. You could fit one anywhere convenienty close to the pump outlet and I’d suggest you buy one with an internal diaphragm and a schrader valve (car tyre type) so you can vary internal pressure if necessary. On my B39C.05 the unit is fitted beneath the pump.

[Salty]

Anyone know if there is an accumulator fitted to a 2014 Vision 46?

I cant seem to find one despite tracing all the fresh water lines so I'm pretty sure I don't have one. Are the ones you guys talked about an after market fit?

Thanks

Some friends of mine had a slightly smaller Vision than yours, but of the same age, and they also did not have an accumulator fitted. I suspect the circuitry on the newer pumps has obviated the need for such a tank, and their pump did not pulse either.

[Kibo]

Thanks Salty and Pea-Jay   I will investigate further