"simon beer" wrote in message
...
Would someone be able to tell me please what a negative head pump does
over
a so called ordinary pump or I suppose what is negative head. Is it just
when the pump is positioned lower than where you are pumping to? many
thanks

--

take off your trousers to e-mail me


I suspect you may be referring to a negative head shower pump unit?
If so this is capable of being used with a shower with the shower head
higher than the water storage tank. Operation is achieved by the pump
responding to a pressure switch at the outlet of the unit. When first
connected the pump will run until the downstream pipework is up to a preset
pressure when an inbuilt pressure switch will stop the motor. A non return
valve built into the unit holds the pipework "full" and retains the pressure
therein. Opening a valve (turning the shower on) releases this pressure so
the pump starts up in response to the pressure switch and runs until the
valve is closed when the pressure builds up aginst the shut valve and the
pump stops again.
Dripping taps cause pulsing of the motor which can be very annoying
Ordinary shower pumps are used where a trickle of water will flow when a
shower valve opens. This trickle operates a flow detector and the pump cuts
in. Shutting the valve stops the flow and the motor stops.

HTH