I get 0.7 bar water pressure from the header tank, but I want 3.0 bar of pressure (I need that much to make the system work properly).

So I need a pump to go with the pressure tank.

Obviously (to me) a pump that will give a 30 metre head is going to work. But will a pump that gives 23 metre head work?

My theory says that the pressure into the pump is equivalent to a 7 metre head, so if the pump will give a further 23 metre head that makes 30 metre head, or 30 bar of pressure.

Am I talking nonsense?

I am not sure that the input pressure is relevant, it is not cumulative.

It is the output pressure that you need to look at.

Also check the pump can handle the volume you require.

I was unsure if I could add the input pressure to the pump figure.

Decided to go for a pump that can give a head of 36 metre, assume I will get 3.6 bar. It gives over 140 l/min.

We want to supply 10 condo units with enough water that everyone can shower at the same time ................. no more comments.

Actually the Grundfos type pump does pass input pressure.

For MQ3-45 - The maximum internal pressure allowed is 110psi. The maximum pressure generated is 65psi,

therefore, maximum inlet pressure is 110 - 65 = 45psi.

If supply pressures greater than this are present, install pressure-reducing devices at the MQ inlet.

Remember that inlet pressure adds to the MQ pressure, so with a 40psi inlet pressure supplied to the

MQ3-45, discharge pressures can reach approximately 105psi (65 + 40psi).