Shower pump problems?

[Blocky]

Hi
I have cut into existing shower pump pipes to add another shower while an ensuite shower is isolated.
The new shower is a traditional one with a. rigid outlet. The problem is that the pump only kicks in when the bathroom taps are turned on. It works fine if you disconnect the inlet pipes. The pump is a grundfos 2 bar with 22mm connections.
Any ideas is much appreciated.
Cheers.

 

[BLOD]

Sounds like not enough flow through shower to turn the pump on, how many litres a minite are you getting through the shower outlet ?

 

[Killy Bing]

Have you boosted the entire bathroom by any chance?

 

[Blocky]

Sounds like not enough flow through shower to turn the pump on, how many litres a minite are you getting through the shower outlet ?

I Haven't measured the litres per min but when it's running it's a good flow.
The problem seems to be getting water through the valve body.

 

[Blocky]

Have you boosted the entire bathroom by any chance?

I didn't do the original installation but the shower is definately the only thing pumped.

 

[Paulus]

It sounds like there isn't enough flow through the pump to open the flow switches. This could be down to the distance between the bottom of your cold water storage tank and the fixed head of the shower not being enough. It should be a minimum of 250mm for the Grundfoss pumps.

Try turning the shower on and playing a magnet at each end of the pump to activate the switches. If this works the chances are that
you may need a negative head pump.

 

[Plumbstar Tom]

Pretty sure it is lack of flow to the flow switches

Negative head kit or maybe you could higher the cold water tank?

 

[Chalked]

Try turning the shower to full cold. If it starts then, the flow switch on the hot side of the pump either isn't there or isn't working.

 

[BLOD]

I Haven't measured the litres per min but when it's running it's a good flow.
The problem seems to be getting water through the valve body.

The shower valve needs a set amount of water passing through it to turn the shower on - measure how many litres a minute you're getting through the shower when the pumps not running and read the pump instructions to see how many litres it needs.

 

[WHPES]

Are there any check valves in the shower mixer you need to remove?