Pulsing shower pump

[Eddy G]

I have fitted a dual impellor shower pump at the bottom of the hot water tank. there is a hot offtake on the tank out let. cold water is direct from cold tank.

the pump/shower starts ok but starts pulsing when the hot water comes through.

i can over come this by turning on the cold water in the bath which is fed from the same pump.

how do i over come the pulsing.
is the pump too big ?
the hot outlet is not directly on the top of the tank - is this the problem ?

thanks for any help

 

[Gasguru]

Post a pic of the cylinder takeoff etc. sounds like it may be excessive air entrainment.
Is it a centrifugal or regenerative (peripheral) impellered pump?

 

[fixitflav]

but starts pulsing when the hot water comes through.

Some people pay extra for that feature