In uk.d-i-y Jeff Lowe wrote:

"Tim Downie" wrote in message
...
Gale Pearce wrote:
You can restrict the outflow side of the pump, but not the intake or
you will burn out your pump prematurely - I use a "ball valve" to
reduce the waterflow on my submersible pump on the line to my filter
Gale :~)

I've already got a restrictor and T-piece on the pump outlet so I can
control the output at present. Somehow it doesn't feel "right" to reduce
the flow this way. I can't help feeling that it's putting extra load on
the
pump. As I have a reasonably hefty lamp dimmer kicking around, I was
just
wondering if using a device like this would be more mechanically
"sympathetic" IYKWIM. (Probably complete nonsense I know).

Since these are just turbine pumps, there is no difference as far as the
pump is concerned as to the location of the restriction on either the input
or output. I would not use a lamp dimmer since these are typically just

Cavitation is a real concern if you put it on the input.
This does cause RAPID wear on the impeller.