Shower Pump wierdness

[OldFartUK]

Im renovating my mother bungalow, she's 90 years old, and has to come to live with us while i do it.

The hot water system is very low pressure, and is prone to getting an airlock if you break into the pipework.

The hot tank is at ground level. The header tank for it is in the loft, and the top of the water in the tank is about 4 metres from ground level. For some bizzare reason. the hot feed to the taps goes UP into the loft across the loft, and then down to the kitchen anf bathroom. The water pressure is low because of this.

A retired plumber said that it coudl be because that a) the taps are cheap chinese taps, which tend to run slow. But he said I might be able to improve the water pressure with a shower pump. SO ive plumbed in a CT55 1.7 bar single impeller shower pump, just above the water out from the top of the hot tank.

It improved the flow in the kitchen, and helps flush out air locks. It hasnt improved the bathroom sink, but thats a mixer tap, and according to the retired plumber the can suffer from constriction of flow because they are bored so small.

However the problem is this. The shower pump kicks in when you turn a tap on, but then just keeps running after you have turned the taps off. To get the pump to stop you need to either turn it off, of close one of the service valves i fitted on the inlet and outlet. Otherwise once started, it just keeps on and on, for hours.

Why doesnt the pump turn off when the taps are off?

Hot water system looks like this;

Untitled

• OldFartUK
• 7 Nov 2013
• 1

pump is a Salamander CT55

Untitled

• OldFartUK
• 7 Nov 2013
• 1

 

[picasso]

You have the pump in the wrong place, if your drawing is accurate you need to take the pump off the vent as nothing allowed on the vent pipe, the picture shows why the pump wont stop.

View media item 68665

 

[Charnwood]

Syphonic action.
Pump is pushing water to the taps, but when taps are closed the syphonic action created through the vent pipe to the tank will continue, making the pump think there's still demand for water.

 

[picasso]

Sorry charnwood but nothing to do with syphonic action, once the flow switch is activated there is no reason for it to switch off.

 

[Charnwood]

Thinking about it again, it's an open pipe, and the pump will continue to run, assuming its an open tap.

 

[OldFartUK]

Ah, I think I understand.

Are you saying that because the expansion/overflow pipe is on the pump outlet side, there is no back pressure created when the tap is turned off fow the pump to sense, because the overflow is open to air.

If that is the case, then would the pump be better moved to the pipe that tracks across the loft, so its positioned with the overflow pipe behind (ie on the inlet side) of the pump? Thus when the taps are shut the inlet side seals, some back pressure is developed and the pump can sense the taps are shut?

 

[picasso]

If your still there

View media item 68700

 

[OldFartUK]

If your still there

View media item 68700

Yes, somone else suggested a Suffolk Flange, which basically requires the pipework rearrnging as you have suggested.

Thanks for all the replies, looks like we have a solution.

 

[Charnwood]

Yes, somone else suggested a Suffolk Flange,

Wrong county, wrong side of the Thames.
Surrey flange.

 

[OldFartUK]

Yes, somone else suggested a Suffolk Flange,

Wrong county, wrong side of the Thames.
Surrey flange.

Ah the one with the Fringe on Top ?