Crosswater Thermostatic shower -only able to get tepid water

28 Nov 2017
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United Kingdom

I have a recently installed Crosswater MikePro 1500C Thermostatic shower running off of a Monsoon 3Bar standard booster twin pump. The Crosswater shower was running ok for a couple of months however has recently started to run tepid even if the temp setting is set to the maximum. If I select maximum cold and then turn to maximum hot, I will get piping hot water for 2-3 seconds before it then reverts to tepid, this is consistent when repeated.

The Monsoon pump also supplies a manual diverter mixer valve for the bath in the same bathroom as the Crosswater, it also supplies an Aqualisa Aquarian thermostatic mixer shower in an en-suite bathroom. Interestingly the bath supply runs without problems with piping hot water when selected, however the Aqualisa is also running tepid even when max hot is selected as per the crosswater.

I have checked the supplies to the Pump and both the hot and cold are running cleanly into and out of the pump, the temp of the hot pipe inlet and outlet are both hot at the same temp when running as are the cold. I have checked and cleaned the inlet filters on the pump, though they were perfectly clean.

I have also checked the filter valves on the Crosswater and have changed the Thermostaic cartridge on the Crosswater with no change.

Not sure what to try next, as the common denominator seems to be the pump, however it is sending hot out on the hot outlet to the showers and the bath is running without issue, nor does it appear to be the filters or the cartridge on the Crosswater.

Any suggestions would be greatly appreciated.
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Is the temperature of your hot water excessively hot ? Maybe too hot for the thermostatic valves to handle. As the manual mixer on the bath is not thermostatic this works fine.
Thank you for the reply. The hot water temp is set to 60 Deg C, which should be within the operating temp for the pump and the cartridge.
Question is ,what is the actual temperature ? You may have the stat set at 60 but if the control gear is not working properly it may well be much higher.
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From a thermometer the actual temp is 58 Deg C
OK that's the aqua a new install as well as the cross water ? And is the pump a new install also? Is the cold supply to the pump from the same loft tank or is it connected to the cold mains ? I assume the hot water is from a cylinder.
The Aqualisa is old, though not frequently used, it has however never had a problem before, it display exactly the same characteristics as the Crosswater in that goes to tepid but up if you switch to max cold then max hot it will flow hot water for a few seconds before then reverting to tepid.

The pump is about 5 years old.

The cold is from a tank in the loft the hot is from a cylinder tank which is heated by a new Worcester Bosch system boiler.
Cylinder is Hercal 245l 1500cm, covered in thick blue/green insulation layer. All other hot water supplies in the house are ok, including two other thermostatic showers (one Crosswater and one Aqualisa -exactly the same a problem two.) the good showers are fed off a separate monsoon pump.
So you have 4 thermostatic shower valves ,all fed from the same hot water cylinder ? Two work fine off one pump. And the other two are problematic fed from a second pump. Regarding the problematic ones ,can you isolate the cold supply to their pump , electrically isolate the pump ,and turn the shower on hot ,high temp setting, on the crosswater, and see what the result is and report should get a weak flow of hot water.
Did as instructed and get a weak flow of hot water on both showers!
Turn electric on to pump , leave cold off, and let cross flow run hot temp for a short while ,no more than 20 seconds and turn off. Do you get hot water at full pump pressure ?
Thanks, seems to run hot, though not on long enough to get to full hot temp.
And is the pressure as you would expect ,compared to when it was working fine ? If so ,we have established the pump is delivering hot water as it should ,but when the cold is introduced the valve is not mixing them as it should ( on both valves ). So either both valves are faulty ( unlikely given you have fitted a new cartridge to what was a relatively new install anyway ,without any difference ) or the cold is overpowering the hot ,which would force closed the non return valve on hot side preventing hot from entering the mixing chamber. So it points toward imbalanced pressures being delivered to both shower valves. Are there any valves / filters between the pump outlets and the showers ? Any flexible hoses on the pipework AFTER the pump ?

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