Pump Runs Mysteriously!

[Alanka]

My friend's loft conversion has a pumped water system. For the last 6 months the pump has been starting for no apparent reason about once every 15 -20 minutes, running for about 30 seconds, then stopping!

Other, possibly connected, problems are that sometimes the water supply to the loft is intermittent, and also the cold shower on the floor below (1st floor) fails if water is being used in loft.

Anyone out there got any ideas?

 

[BLOD]

Could be a small leak from one of the loft outlets, dripping tap etc.
If you can't find a leak try isolating the hot & cold to and from the pump and see if it still does it.

The problem with the shower n the floor below sounds like something could be piped up wrongly, would also check the storage tank is large enough

 

[fuzzy]

check its not desinged to do that, must be something to do with pressure switch otherwise id have thought

 

[Alanka]

Thanks for your inputs, gentlemen! I'm taking a look at the situation over the weekend, and will report back to the forum next week.

 

[Alanka]

As promised, here's an update.

Could find no leaks, and the cold water cisterns in the roof were fine and full. Looking at the pump (a Stuart Turner negative head model) made me want to check the air pressure in the little pressure vessel (that kick-starts the pump under negative head conditions -- which he's got in the loft). He had retained the installation booklet which specified the air pressure as 0.9bar. I undid the schraeder valve and fitted on his bicycle pump, which indicated zero pressure on its gauge. Tried to pump up the pressure, to no effect. Removed the bike pump and tried pressing in the central pin in the schraeder valve -- great fountain of water shot out of the valve! Fault diagnosed! The diaphragm in the pressure vessel had evidently broken, filling it with water.

My friend has ordered a new vessel and hopes to fit it in the week. Should solve the problem -- but if not, I'll report further to the forum.

 

[BLOD]

Sounds to me like one or both of the non return valves built into the pump outlets need replacing.
If the expansion vessel needs replacing as well, then depending on the age of the pump it might be
worth putting these costs towards a new pump.

It would be worth calling the stuart turner tech help line - they're very helpful.

 

[Alanka]

New pressure vessel fitted to pump -- everything works again 100%.

Apart from wear and tear, a possible failure mode for the diaphragm could be that if the air pressure has gradually been falling (due to an air leak via the schraeder valve, say), the diaphragm would be stretched more and more by the water pressure on the other side, without the correct pressure of air to oppose this. That would overstretch it , possibly to the point of destruction.

The instructions with the pump do indeed tell you to check the air pressure every 6 months (I think it said). Nobody does, of course!

It's a thought.