Is it time to buy a new pump?

Griffiths 1 Posts 1 Karma
Griffiths posted this 08 January 2018
We have a Monsoon Universal Twin 3 bar pump in the loft pumping water for our 5 bedroom, 3 bathroom home. Serial number is 0937018-075 Part 46410. The level of the water in our header tank in the loft is about 1.6m above the pump.
I bought this pump as a used item on eBay about 4 years ago after a succession of new Salamander pumps leaked. I am so impressed by this Stuart Turner pump; it is so much quieter, switches on faster and is far better constructed than the plastic Salamanders we had before.
However, in the last 6 months, our Monsoon pump has started to turn itself on every 30 minutes or so for about 5 seconds and occasionally for as long as 10 seconds. But I don't think it is pumping water. I think it is re-pressurising itself. There are no leaks from any taps or cisterns. I have taken the pump apart as far as I can, checked action of the valves, cleaned things up and used PTFE tape around the pressure vessel and switch threads but it continues to switch on every 30 minutes or so.
As you can probably guess, if someone is having a shower and someone else flushes the loo, the person showering gets scalded.  And 2 people cannot shower at the same time. So I realise 3 bar is probably not strong enough for our home.
My questions are;
1. Is there a DIY fix for the fault our pump has today? Or is it towards the end of its useful life? How old is it?
2. If I purchase a new Stuart Turner pump, should I go for 4.5 bar? Would this mean 2 people could shower at the same time and not be scalded when someone flushes the loo? 
3. If I purchase a new pump, should I buy the Universal version with the pressure vessel or would the standard version be just as good (we have a 1.6m head of water above the pump). Does the Universal pump switch on faster than the standard in response to water flow? I would not want to lose the instant response we enjoy today with our Universal pump.
Thanks for your advice
PumpAssist 256 Posts 187 Karma
PumpAssist posted this 09 January 2018

You need to close the isolation valves on the two hoses above the flow switches (outlet side) and see if the pump still cycles on and off. If it does then the non return valves in the pump have failed. If the pump stays silent for at least 30 minutes, then it's not a pump fault and something on your system is losing pressure.

The pump was manufactured September 2009 and so at that age we would recommend replacing the pump.

Turn off the pump and run a tap to release the pressure and then try every tap and shower in turn to see how much water you get out of them without the pump. You will need a Universal pump if you do not get a good flow out of everything that you are pumping to, under gravity. Standard pumps require a good gravity flow out of the taps/shower to activate them so if you don't have one, it won't work.

The size of the pump will depend on the flow of water out of the showers. You would need to add up all the flows of everything you want to run together and then look at the performance graph and see what pump will give that flow rate and at what pressure. If for example it is 25 lpm then a 4.5 bar will give you about 2.5 bar pressure, the 3 bar will give 1.4 bar. Bear in mind if you are only using a low flow with a larger pump then the pressure will be very high. The bigger pump will also be noisier and will need to be connected to the cylinder differently (see installation manual).