Monsoon 3.0 bar pump uneven flow rates hot/cold

Norman1945 1 Posts 1 Karma
Norman1945 posted this 08 February 2018

I have a Monsoon 3.0 bar pump gravity fed on hot and cold yet flow rate from cold side is much greater than hot side.  This is pumping to an Aqualisa Acquamixa Thermo shower. If I remove shower head and turn the thermo control from hot to cold the flow rate greatly increases from the shower tube!  Consequently the shower runs cold even at maximum heat setting unless the tap is fully open which is far too high a flow rate. If flow rate is reduced at same temperature setting then shower runs cold.

It seems that the flow to the hot side might be restricted yet there is only about 3 or 4 ft of pipework between the pump and the shower control and no restrictive valves etc in the plumbing!

Could this be a pump fault?  The pump also goes to a Bristan mixer shower at the other end of the house and this works fine with good temperature control!  We had an Aqualisa engineer in and he was sure it was a flow problem between the hot and cold sides.

Any help or ideas much appreciated!

PumpAssist 230 Posts 161 Karma
PumpAssist posted this 12 February 2018

As the pump works fine on one shower, it can't be a fault with the pump.

The monsoon pumps will generate the same flow and pressure through out their life as the parts don't normally wear. You could have a blocked filter on the pump of course but you would tend to get the problem at everything you are pumping to.

It's more likely that there is a blockage at the shower on the hot side (possibly filter) or the shower valve is faulty. Certainly it would point to the shower valve if you are unable to adjust the temperature correctly but you would have hoped that the Aqualisa engineer would have found something wrong with it.

It could be that the cylinder isn't breathing correctly and the bottom of the cylinder is chalked up and restricting the flow of the cold water into the cylinder. If the Aqualisa shower uses a much higher volume of water than the other shower that could explain why it is affected more. The way to test this would be to get a plastic bag, blow it up and tape it to the end of the vent pipe hanging over the cold water tank in the loft. If you run the shower and the air is evacuated from the bag then it tells us the cylinder is pulling air down the vent pipe due to a blocked cylinder.