shower pump runs on (no leaks)

[adamski2]

I have a Stuart Turner Monsoon twin impellor 3bar pump. It has run perfectly for two months, but suddenly started to run on after turning off the shower. It is installed correctly, there are no water leaks, and I have run through the process of clearing any air by running water through fully hot, then fully cold for 10 minutes each with the pump off (but all valves open). I have also turned down the hot water temperature to ensure no bubbles from boiling. Closing the outlet valves on the pumps outlet hoses turns off the pump, so I believe the pump itself is working fine.
The odd thing is that after I turn off the shower, with no water running; if I then turn the shower mixer knob to fully cold, then this switches off the pump.
Any ideas what can be causing this?

 

[Madrab]

Sticking flow reed sensor?

Give ST a call, their customer support is usually excellent.

 

[adamski2]

thanks - I did call them and they say the pump and flow reed sensor are working fine, as the pump turns off when the outlet valves on the pumps outlet hoses are turned off.
I actually have two showers connected to this, and for shower 1 to work, it only switches off when the temperature knob is turned to fully cold. Shower 2 works correctly but only if the temperature knob on shower 1 is turned to cold. If not, then this also causes the pump to run on.
So I am thinking it must be something to do with the temperature mixer control on shower 1, but I am mystified why this could cause a pressure drop which is what must be making the pump run on

 

[Madrab]

If ST are saying the switch is ok then need to look at it systematically.

The only thing you are doing when turning the stat to cold on shower 1 is turning off the hot inlet through the cartridge. Therefore the flow valve or cartridge must be passing HW when open and that is being sensed by the pump. At least 0.6l/min. What type of shower?
Do you have a drip from shower 1? If not the only place it can be passing into is the cold feed but if that's balanced then that shouldn't happen, I assume it is fed from a Cold Water cistern and a HW cylinder?
Do you get any overflow from the cold cistern? Any damp patches anywhere?
That water must be going somewhere.

 

[adamski2]

Hi Madrab,
>> What type of shower?
Not sure the make (was installed over 15 years ago) but looks like this
http://t0.gstatic.com/images?q=tbn:ANd9GcQlsKEttWctX_x26VnTVL0N9P4Omci6oG_Qhngz_qx8jexwVR6niw
i.e. one knob for turning water on, the other for controlling temperature.
There is no overflow from the cold cistern.
There are no drips from either shower, no damp patches anywhere. I have looked everywhere (except under the floorboards where the pipes go between airing cupboard and bathroom) and cannot find any leak. It could be under the floorboards, but I would have thought that this would have come through the ceiling at least as a damp patch by now if this were happening.
The system is fed from a Cold Water cistern and a HW cylinder, both feeding directly into the pump. the feed from the hot water cylinder is a branch off the main feed out of the top of the cylinder, which is one of the accepted methods in the Stuart Turner installation manual.
I am reluctant to take up floorboards and dismantle the shower, but it is looking like that may be the only option.

 

[Nevs]

More often than not it's the crappy rubber washers that Stuart Turner fit to the flow switches, which distort & stick when they get a bit too hot. You can get much better silicone heatproof washers on eBay, cheaply:-

https://www.ebay.co.uk/itm/133324946757

Read more: https://www.diynot.com/diy/threads/...er-pump-not-turning-off.425811/#ixzz7HjoRa4HF

 

[Madrab]

Read more: https://www.diynot.com/diy/threads/forum-rules-general-info.19448/

Point 8

 

[Nevs]

Your point being...? Still relevant, still an issue causing problems for a lot of people.

 

[Madrab]

The point is it's the rules of the forum. Normally a new thread would be started and then a link to the old one would be added.