"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?

See the makers, but I doubt it. Get a pump with a lower switching
differential. Also put a non return valve just before the pump. Between the
valve and pump install a potable pressure vessel. This will help prevent
pump cavitation and a more even water distribution. Some pumps come with
the vessel as a set. How is hot water supplied? Via a cylinder? Vented?
Unvented?

If you get anew pump use the old as a backup.

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?

Yep. 1 bar = 10 metres