Shower pump kicks in when I open sink tap

[SIDD]

Hello,

I am confused if this is a fault or normal..and if its a fault then how to fix it..!! your comments will be highly appreciated.

I have a shower pump fitted in the shower (i dont know what make as I didnt get it fitted and it is underneath the tub towards the wall so I cant even see it..!!). When I open the hot water tap in the sink (which is beside the shower) and close it...the pump kicks in for a second and stops. This does not happen all the time but every once in a while.

I moved in this property 6 months back and this has started happening in just the last week or so, is this a fault developing or normal..?? if its a fault how do I go bout fixing it..?

Thanks

 

[rebelbuttmunch]

I had the same problem. I think its to do with a pressure drop. My pump just engaged for half a second or shorter. I just lived with it I'm afraid.

 

[SIDD]

I had the same problem. I think its to do with a pressure drop. My pump just engaged for half a second or shorter. I just lived with it I'm afraid.

I dont mind living with it as long as the pump does not packup one fine day..!!

 

[Armo74]

Is the hot feed for the shower an independant one? Not feeding any other taps.

 

[SIDD]

Is the hot feed for the shower an independant one? Not feeding any other taps.

Looks like it..as the sink hot water pipe is coming from underneath the floor (concrete)

 

[SimonH2]

It's the sort of thing that can be caused just by having air in a pipe. When you turn off the sink tap, the flow of water has to stop - which it doesn't like doing as it has inertia. When you turn off a tap, a combination of rising pressure due to the flow stopping and a momentary surge in pressure due to water inertia will result in water flowing into the pipe which has air in it - pressurising the air. If that pipe happens to be between the flow sensor for the shower pump and and the shower valve then it can trigger the pump to start.
Normally nothing happens because water isn't compressible - so there can be no flow into the shower branch.

The same thing can cause a combi to fire up when turning off a cold tap.

 

[SIDD]

It's the sort of thing that can be caused just by having air in a pipe. When you turn off the sink tap, the flow of water has to stop - which it doesn't like doing as it has inertia. When you turn off a tap, a combination of rising pressure due to the flow stopping and a momentary surge in pressure due to water inertia will result in water flowing into the pipe which has air in it - pressurising the air. If that pipe happens to be between the flow sensor for the shower pump and and the shower valve then it can trigger the pump to start.
Normally nothing happens because water isn't compressible - so there can be no flow into the shower branch.

The same thing can cause a combi to fire up when turning off a cold tap.

yep..that makes sense...!!