My mum is in the process of starting to get a new bathroom fitted

The taps she likes for the bath she has been told that it operates at 1 or 1.1 bar pressure.

Her system is gravity fed and the pressure at the min in the bath is really good.

How can i tell if the new tap etc will work ok with the gravity fed system we have?

The tank in the roof space from the top of the exisiting tank to the bottom of the water storage tank is about 10 foot

The plumber has said putting in a good pump that will last is quite expensive and we would like to avoid this if possible or other option is to change the bathroom tap/shower fitting etc.