Low power shower

[sadders]

We have 2 bathrooms both on a pumped system.

In one there is a thermostatic mixer shower. When it is turned on it is a dribble and the pump doesn't come on until you turn the sink tap on. Then the shower pressure is OK but not brilliant. When you turn the sink tap off the shower stays OK until it has been turned off, then same again.

In the 2nd bathroom the shower is on a non thermostatic mixer and takes the skin off your back. Brilliant.

What's up with the 1st one?

 

[stem]

The pump is started by an integral switch that detects water flow when a shower is turned on. I suspect that for some reason the flow through the first shower is not enough to start the pump, until the tap is turned on. (I'm assuming the tap you refer to is also fed from the same pump as the shower and so the pump only pumps the hot water) once the pump has started, the additional flow through the shower is enough to keep it going.

If it used to work, has anything changed that could reduce the flow? Have you fitted a new shower head that uses less water, changed the spray setting, or is the head getting blocked with limescale?

As a test of this theory, you could unscrew the shower head from the first shower and turn it on. Does the pump start then?

It's possible that the pump flow switch is becoming less sensitive, and because the thermostatic shower mixes hot and cold then the flow may not sufficient to trigger it. The manual one may start with a full flow and so it kicks in.

Also are both bathrooms on the same level? If the one that doesn't work is a floor higher that may explain the reduced initial flow.

 

[Ropes]

It's worth checking out the poor pressure shower for blockages on the filters, outlet of the shower or a scaled up shower head. If it's easy to disconnect the shower, I'd isolate and disconnect it then let it run into the bath/shower. If it works fine then there's an issue with shower, and if there's still a poor flow with no shower connected then as Stem says then flowswitch probably on it's way out.

 

[sadders]

Thanks for the replies.

I will take it apart and check the filters. I think I will also play with the settings for the thermostatic settings to see if it helps.

Thinking about it, the tap pressure (hot) is lower than the other room as well.

Is there an easy way to check all the pipes without ripping everything up or is there a product to throw in to get rid of whatever might be there?

edit: the hot power in room 1 has always been lower than room 2, it's just this having to turn the tap on to get the shower going that prompted the question)