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Domestic water problem - how do I cure a pulsing pump?


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Our domestic water is pumped by a Jabsco Parmax 3.5; there's an accumulator on the hot side but not on the cold.

The cold runs fine to the first outlet (bath tap) but pulses badly at the basin and sink taps. Bath hot water is pretty good as are the hot outlets for the sink & basin - but when the accumulator pressure is 'used up' as it were and the pump is working alone there's pulsing again at the smaller hot feeds.

 

I've disconnected the sink cold tap and the water flows perfectly - the problem seems to be in the microbore connections between tap and 15mm piping. They are constricting the flow or causing back pressure on the pump I guess.

 

What's the solution? Do I need a bigger pump? New taps (expensive and fiddly to fit)? Another accumulator? I don't want to go randomly buying bits without a reasonable chance that I'm on the right road.

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Our domestic water is pumped by a Jabsco Parmax 3.5; there's an accumulator on the hot side but not on the cold.

The cold runs fine to the first outlet (bath tap) but pulses badly at the basin and sink taps. Bath hot water is pretty good as are the hot outlets for the sink & basin - but when the accumulator pressure is 'used up' as it were and the pump is working alone there's pulsing again at the smaller hot feeds.

 

I've disconnected the sink cold tap and the water flows perfectly - the problem seems to be in the microbore connections between tap and 15mm piping. They are constricting the flow or causing back pressure on the pump I guess.

 

What's the solution? Do I need a bigger pump? New taps (expensive and fiddly to fit)? Another accumulator? I don't want to go randomly buying bits without a reasonable chance that I'm on the right road.

I assume by pulsing you mean that the pump switches on and off quickly.

 

 

Another accumulator on the cold side will damp down any pulsing caused by pipes which are too small, but I'm not sure why the small pipes at the sink cause pulsing at the bath. Does the bath also have small pipes to the tap?

 

With a decent sized accumulator on the cold, at low flow rates the pump should run for quite a while, then shut off ( whilst the accumulator will then supply the flow), then come back on again after the accumulator is emptied. At full flow rates it may either run continuously, or run for a much longer period before it shuts off.

 

N

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Our domestic water is pumped by a Jabsco Parmax 3.5; there's an accumulator on the hot side but not on the cold.

The cold runs fine to the first outlet (bath tap) but pulses badly at the basin and sink taps. Bath hot water is pretty good as are the hot outlets for the sink & basin - but when the accumulator pressure is 'used up' as it were and the pump is working alone there's pulsing again at the smaller hot feeds.

 

I've disconnected the sink cold tap and the water flows perfectly - the problem seems to be in the microbore connections between tap and 15mm piping. They are constricting the flow or causing back pressure on the pump I guess.

 

What's the solution? Do I need a bigger pump? New taps (expensive and fiddly to fit)? Another accumulator? I don't want to go randomly buying bits without a reasonable chance that I'm on the right road.

I don't know what others think, but I reckon it would be unusual to have an accumulatore fitted to the hot water side only. Accumulators are normally fitted within a short distance of the pump. Bear in mind that the pump normally provides pressure to both hot and cold systems.

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There is quite possibly a non-retur nvalve on the feed to the calorifer. If this is the case the existing accumulator on the hot side will do nothing to help the cold side. Either fit another accumulator on the cold feed (and check pressure settings - can be lower than the hot side which needs to be a bit below the PRV pressure - probably 3 bar) or take out the NRV. Microbore pipe for the water system doen't help either - really you need at least 15mm and preferably 22mm pipe run with 15mm teed off for taps etc.

 

 

Accumulators are normally fitted within a short distance of the pump. Bear in mind that the pump normally provides pressure to both hot and cold systems.

 

They can be pretty well anywhere , allowing for NRVs. Mine are under the bed, about 10 metres from the pumps.

Edited by dor
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By all means fit an accumulator in the cold feed but it will only extend the puling period. If the greater the pump supply compared with the flow from the outlet the greater the pulsing. In my view you need a lower output pump. I am not even convinced that turning the pressure down will help because the pump will still have the same delivery volume.

 

My advice is to learn to accept the cycling as normal.

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Are you sure it's an accumulator on the hot leg of the system. It could be an expansion vessel, they look very similar and are basically the same but they are set up differently and do a different job.

 

An EV is set at a pressure below the PRV pressure on the calorifier but above the pump pressure. It can therefore absorb the expansion of the contents of the calorifier as it gets heated up, but can do little to smooth pressure fluctuations during pump operation. It's there to protect the calorifier from extreme pressure variations and so prolong its life.

 

If an EV is all you have on your system, adding an accumulator sounds like a worthwhile idea.

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By all means fit an accumulator in the cold feed but it will only extend the puling period. If the greater the pump supply compared with the flow from the outlet the greater the pulsing. In my view you need a lower output pump. I am not even convinced that turning the pressure down will help because the pump will still have the same delivery volume.

 

My advice is to learn to accept the cycling as normal.

Tony, I tried turning the bath cold tap on and then opening the sink cold - no pulsing - so maybe that proves your point?

And you're correct Trackman it's an expansion vessel in the hot side. Apologies.

 

The Jabsco doesn't seem to me to be the 'quiet running' pump they claim - pretty noisy I would say even when not pulsing. Maybe my imagination but our Sureflo was quieter. Has anyone tried this fancy Jabsco Sensor-Max which claims to be silent running 'under normal use' ...whatever that means.

Edited by starman
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The problem seems to be down to me fitting monobloc taps which have very small bore flexible connectors and small internal diameters which restrict the supply and 'trick' the pump into thinking it's reached shut-off pressure so it pulses on and off repeatedly. (Tried a temporary old school single tap and water runs fine!)

What to do about it is the problem - even the taps that claim to work on low as well as high pressure - e.g. they are less restrictive in bore - seem to come with narrow flexible connectors.

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I have a Jabsco. It used to pulse. I adjusted the screw. It stopped. 5 of us shower daily (sometimes). There is plenty of pressure. Try adjust the screw on the top of the pump.

 

 

ETA. If it pulses while all taps are closed, you have a leak.

If it pulses when one tap is open, tweak the screw,

Edited by DeanS
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Problem solved! Have fitted Jabsco Sensor-Max electronic pump which speeds up and slows down delivery to suit demand. And needs no accumulator. Taps now running well - smooth and fast delivery - and and pump is also very quiet. Expensive pump but worth it.

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Problem solved! Have fitted Jabsco Sensor-Max electronic pump which speeds up and slows down delivery to suit demand. And needs no accumulator. Taps now running well - smooth and fast delivery - and and pump is also very quiet. Expensive pump but worth it.

 

Glad you're sorted.

My screwdriver cost £2 :) (tongue in cheek cause Im jealous)

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  • 4 years later...

Hi all .

And how' Dean? .

I recently had my jabsco pump running on after the tap was turned off and cycling when not in use took me weeks to work out I have no leaks .I have just bought a shurflo and now have pulsing on the kitchen tap and the washing machine . The toilet ,shower ,and bathroom basin are all fine . I have had to half close the stop valve to shop the pulsing . Not sure if that is the ideal answer to it though ? 

Regards Greg 

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3 minutes ago, Greg & Jax said:

Hi all .

And how' Dean? .

I recently had my jabsco pump running on after the tap was turned off and cycling when not in use took me weeks to work out I have no leaks .I have just bought a shurflo and now have pulsing on the kitchen tap and the washing machine . The toilet ,shower ,and bathroom basin are all fine . I have had to half close the stop valve to shop the pulsing . Not sure if that is the ideal answer to it though ? 

Regards Greg 

An old thread. Seems odd that the pump would do that unless you have a leak, even if its an internal pump leak.

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Fit a lower output pump?. If the pump delivers more water than can escape through the tap then the pressure will continue top build and the pump will cycle. You can extend the on-off period by fitting a correctly pressurised accumulator. Sometimes messing with the pressure switch can elp. However I think its situation normal and not worth worrying about.

1 minute ago, rusty69 said:

An old thread. Seems odd that the pump would do that unless you have a leak, even if its an internal pump leak.

I think they are talking about cycling when an outlet is open. Not random running with everything closed.

Edited by Tony Brooks
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1 minute ago, Tony Brooks said:

A lower output pump. If the pump delivers more water than can escape through the tap then the pressure will continue top build and the pump will cycle. You can extend the on-off period by fitting a correctly pressurised accumulator. Sometimes messing with the pressure switch can elp. However I think its situation normal and not worth worrying about.

I think they are talking about cycling when an outlet is open. Not random running with everything closed.

Ah ok. I thought "cycling when not in use" meant taps closed. Perhaps Greg could clarify? 

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Thanks for replying .

Yes the jabsco problem was very odd it's about 3 years old and  over the last few weeks got gradually worse.  Caused no end of trouble trying to find the none existent leak .it would over run after the tap was turned off then cycle while nothing was being used not fully pumping but a short run every minute or so for hours .

Edited by Greg & Jax
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4 minutes ago, rusty69 said:

Ah ok. I thought "cycling when not in use" meant taps closed. Perhaps Greg could clarify? 

Yes, that is why he bought a new pump, then he had the pulsing on certain outlets.

 

3 minutes ago, Greg & Jax said:

Thanks for replying .

Yes the jabsco problem was very odd it's about 3 years old and  over the last few weeks got gradually worse.  Caused no end of trouble trying to find the none existent leak .

And a plumbers one way valve on the inlet side between strainer and pump may well have solved the issue without a new pump. The lower output (no cycling with tap open) on the old pump suggest there may have been a loss of outlet volume and the running with no leaks suggests leaking valves in the pump. I fit such a valve as standard if I ever have to fit a new pump. (Along with a remote pressure switch but that’s another topic!).

Did you check the PRV on the calorifier for leaking before buying a new pump? In your case it would have been OK but they do scale up and weep giving the random pump running.

Edited by Tony Brooks
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13 minutes ago, Greg & Jax said:

Thankyou for the quick reply,s .

I will look into fitting the valve .

Regards Greg. 

No need to while the pump is staying off with the taps closed, especially as many strainers fit onto the pump inlet, Just bear it in mind the next time the pump runs at odd times and there are no leaks.

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