"Sparks" wrote in message
...
"Mark BR" wrote in message
...
Can a plumber give me a simple answer to what I think is a simple
question?

I'm working with a building in Thailand to improve the water supply.
Currently we have a pump and pressure tank that can just get up to
2.5Kg/cm (2.5 bar). This pressure is just enough. Problem is when it
reaches pressure it switches off and only comes back at 1.7 bar, not
enough for most rooms. So we get a varying water supply from a trickle to
a surge. If we leave the pump on continuously we use far too much
electricity.

We have a lovely electric pump, 8 amp so plenty of power, and a header
tank 4 metres above the pump.

Can I just change the water pump part - is that the impeller?

If I change it for a pump that can get up to 3.5 bar is that the same as
a pump that can give a 35m lift?

Thanks,

--
Mark BR

You could install a flow switch between the pressure vessel and the rest
of the plumbing, wired so when it detects flow, it turns the pump on (So
in parallel with the current pressure switch).

This way, the pump will always run when you are running water, and only
turn off when the pressure has reached the setting of the pressure switch
and there is no water flowing out of the pressure vessel.

I have this setup with my irrigation system setup, it seems to work well
for me!

I was about to suggest that. You are right, a simple flow switch can solve
the problem and a little re-wiring around the pressure switch.