Help needed - water pump does not prime / stays on

[EugeneR]

I drained the pipework for winter; now, having re-filled the water tank, the water system is not working. The symptoms are:

- At first, the pump refuses to prime unless I suck some water into the system manually. The pump is around 30cm above tank level, fwiw.
- Once it gets going, the flow is OK but not as much as it used to - enough for one tap, nothing more.
- Cold water has a constant stream; hot water is there but splutters a little.
- Once going, the pump stays on even after all taps are closed - yet it does not sound like much water is going through pump i.e. not the usual pumping noise. And it does not achieve switch-off pressure, it seems.
- No obvious leaks except for a slow drop from the pump or around it - around 1 drop every 30 seconds - which was there last season already so unlikely to be the cause here.

My initial diagnosis was air in the system, most probably in the calorifier , but after keeping the hot water tap open for 10 minutes, it continued to splutter. Clearly, the air is not coming out by itself and, after closing all taps, the pump continues to run until I switch it off manually.

What could be the issues and what should I do? I'm not familiar with this type of plumbing connections (yet, the other boat has push-fit connections which are easier) so don't want to start taking things apart just yet - I bet there's a simple solution for this...?

 

[rafiki_]

It could be that the system is still building up pressure? I used to turn the taps on and off on my old Sunline that was also a little reluctant to build up pressure after being drained in the winter. I put it down to filling the calorifier, which took time.

 

[EugeneR]

I was thinking the same however I've had 10+ minutes of water coming out the hot-water tap already, plus 3+ minutes of pumping with all taps closed when it also sounded different than it's normal "getting up the pressure".

It's a Shureflo Aqua King Standard made in 99 so perhaps it needs a service kit / replacement; however the fact that it stopped working while being drained seems a bit coincidental. For now, I'm assuming there may be a trick I don't know and hoping that someone will tell me what is or an easy way to troubleshoot...

On the other side, when pumping, it's slower than usual so there may be an issue with the pump which also causes the other effects.

 

[rafiki_]

Is your accumulator working ok?

 

[Spi D]

If you work systematically you'll be able to detect the culprit. Remove the hose from the pump outgoin line, block it and start the pump. Following steps would be steps would be after the next device/joint and so on.

If no apparent leaks, I'd expect the pump or pressure switch to be bad. While available as spare parts it might prove wiser to replace the whole pump.

This may be of use in getting to understand the internals and or select a replacement (plenty available from more manufacturers)
http://www.shurflo.com/files/Educat...s/pds-Aqua King Standard 12v 3901-0206 16.pdf

 

[henryf]

I suspect there is a leak somewhere on the input side of the pump.

If you have a plastic pre-filter that would be the first place I would look. Failing that I have seen times when the head of the pump has been damage by ice when allowed to freeze.

There is an internal pump membrane as well.

15 years is a long time for a water pump and the fact it was leaking last season is not a good sign.

I doubt it would be a faulty accumulator tank, that would normally manifest it's self as a pump which ran every time the tap was opened, as opposed to water flowing for a while and then the pump running once the accumulators store had been depleted.

Henry

 

[Spi D]

If you have a plastic pre-filter that would be the first place I would look. Failing that I have seen times when the head of the pump has been damage by ice when allowed to freeze.

Good point. Actually happened to me on a previous boat without actuator tank.

 

[superheat6k]

I fitted a new multi diaphragm Shurflo style pump a few months ago to replace an ancient Par belt driven pump (free to a good home anyone who wants it for spares but needs new diaphragm).

But the new pump developed a small drip when running, and seemed to always have air spitting from the taps. The supplier immediately replaced the pump, and not only was the leak cured, but also the spitting, so I suspect it had a misaligned bearing or seal on the drive shaft. A worn bearing or seal could have the same effect.

 

[cryan]

It could be a damaged diaphragm or sticky pump valve? You should be able to check and replace these quite simply.
Is the pump not making the cut out pressure or is the switch not sensing the pressure? It is not unknown for pressure switches to slip out of calibration so if you don't have a system pressure gauge it might be an idea to fit one. However I'm not sure you can adjust it on those Shurflo pumps?
If you didn't flood your system properly when you re-commissioned it you may have large pockets of air in places like the calorifier. If your able to vent that locally at the calorifier do so. It is sometimes also worth making sure your accumulator bag is topped up with air via a bicycle pump although as stated above no air pressure would tend to lead to instant pump cut in.

 

[volvopaul]

If you drained the hot tank have you twisted the blow off valve to vent the cylinder? Try this as it may be the system is trying to pressurise compressed air at the top of the cylinder.

 

[stelican]

Check for airleak or blockage at inlet filter on pump

 

[EugeneR]

I found the issue - the pump is leaking water but also air on the vacuum side, preventing it from priming unless the water level in the tank is near that of the pump.

Given its year of manufacture - strangely, a few years older than the boat - I've ordered a new one. I was surprised to see how much cheaper ASAP was compared to others!

The new one comes in 30 and 45 PSI flavors whereas the old one was 20 PSI... hope the rest of the system can cope with the increase to 30...

 

[volvopaul]

I found the issue - the pump is leaking water but also air on the vacuum side, preventing it from priming unless the water level in the tank is near that of the pump.

Given its year of manufacture - strangely, a few years older than the boat - I've ordered a new one. I was surprised to see how much cheaper ASAP was compared to others!

The new one comes in 30 and 45 PSI flavors whereas the old one was 20 PSI... hope the rest of the system can cope with the increase to 30...

By increasing the pressure you may find the tank blow off valve needs replacing . I'd gave stuck with 30 psi one.

 

[mad_boater]

I found the issue - the pump is leaking water but also air on the vacuum side, preventing it from priming unless the water level in the tank is near that of the pump.

Given its year of manufacture - strangely, a few years older than the boat - I've ordered a new one. I was surprised to see how much cheaper ASAP was compared to others!

The new one comes in 30 and 45 PSI flavors whereas the old one was 20 PSI... hope the rest of the system can cope with the increase to 30...

+1 For ASAP prices

 

[EugeneR]

By increasing the pressure you may find the tank blow off valve needs replacing . I'd gave stuck with 30 psi one.

Turns out this is exactly what happened. New pump is 30psi I.e. 2 bar, calorifier valve is meant to be 2.5 bar but blows open. Is the valve likely to be old and more easy to blow open?

New valve seems to be 2/3 the pump's price... I guess I could test the pressure first. Any idea how, without spending money first?

 

[stelican]

valve

Turns out this is exactly what happened. New pump is 30psi I.e. 2 bar, calorifier valve is meant to be 2.5 bar but blows open. Is the valve likely to be old and more easy to blow open?

New valve seems to be 2/3 the pump's price... I guess I could test the pressure first. Any idea how, without spending money first?

look on line ebay trianco boiler spares, blow off valves from £12.50

 

[David2452]

look on line ebay trianco boiler spares, blow off valves from £12.50

That's over 50% more than I charge retail for a 3 bar PRV :surprise: Must put my prices up.

 

[David2452]

I guess I could test the pressure first. Any idea how, without spending money first?

Simple, remove the hose from the output side of the pump and connect it to a Rothenberger pressure tester, at least that's what I do, if you know a plumber he/she will have one, you could probably use a radiator pressure tester too if you know somebody who has one, possibly even a tyre inflator pump with a gauge. In the absence of the right kit and for what a PRV costs (under a tenner retail) you may as well just change it.