fitting a shower pump

[neilinbal]

have just moved into a new house where i have a gravity water system. my problem is that the shower pump (it only runs the shower) keeps running when shower is off i've had a plumber who says it's had it as it's about 10 yrs old and they don't make that pump anymore. the thing is the pump is in the loft directly above the shower i can see why this was done (easiest way) but will a straight forward swap work so i can do it myself or will it have to be moved. thanks
here's a pic to help

 

[danplumb]

If it works well where it is then a swap will be fine, aslong as it the same type of pump.

 

[neilinbal]

cheers for quick reply.
do i just need a pump that has the same output think it's 1.5 bar. i'm a bit at a loss what a twin impeller & single etc is. so any help please.
cheers

 

[Nige F]

twin impeller pumps H+C ...... single, pumps mixed water after the shower er, mixer Neg. head ones work above the shower head ( and below come to that ) using pressure in the pipeline : Pos. head ( ordinary ) ones rely on flow through the pump to start it running

 

[neilinbal]

thanks again. sorry for being a numpty but if my pump is above the shower head on same level as bottom of tanks in loft does that mean i need a negative head pump.
cheers

 

[ivixor]

So long as it's below the level of water in the tank it's not a negative head.

However it might not be enough pressure to reliably trigger the pump start.

I got away with a non-negative pump at rafter level in the loft, you do sometimes have to open another tap as well as the shower to kick things off however.

 

[neilinbal]

thanks for replies guys think i'll go for a positive head pump as they are loads cheaper n just pipe everything up same as before.
cheers

 

[kvsalamander]

its safer to go with a negative head pump where,

you are mixing pumped hot with mains cold (eg mixer shower)

anywhere with a solenoid or flow restrictor like an electric shower or washing machine.

anywhere where the highest point in the system is within 600mm of the base of the cold water cistern

anywhere with a natural flow of less than 2/min

(for our pumps anyway)

hope this helps

 

[neilinbal]

Helps a lot. Cheers everyone