Single or twin impeller shower pump?

[yaff]

I have a manual mixer shower pumped with a single impeller negative head pump (my cold water tank is in the airing cupboard and the shower head is way above that height)

Currently, the cold from the cold water tank goes straight to the mixer valve, the hot from the hot water cyclinder goes via the pump, then to the mixer valve.

I need to change my pump and note that twin impellers are more common than single ones, with regards to installing it is it a 'simple' case of disconnecting the cold water pipe from the valve, connecting it to the imput end of the pump, connecting a pipe to the output end, then connecting that back into the valve, as with the current hot pipe?

 

[cross thread]

cold is feed to the pump from the cold tank.make sure your tank is boi enough capacity. have you checked out venturi showers that dont use a pump

 

[yaff]

I only have a 25gal tank so i'm guessing this is why there is a single impeller pump fitted i dont have room for a bigger or secondary tank), my hot water tank which is the one being pumped is much smaller than my cold tank, i did have the concern that if i pumped the cold aswell the cold tank would empty faster than it could replenish.

I dont have so much of a problem with the hot as once the hot runs out (which to be honest i have never stood in the shower long wnough for this to happen) i would turn the shower off, that would never actually run out of water