How can I fix water pressure from downstairs to upstairs?

I guess that you are talking about cold water?

As a rule cold water pressure is normally better downstairs than upstairs assuming its fed from a cold water tank in the loft. due to a better head of water.

Mains water into the house, normally at the kitchen tap, and used for drinking, will be the highest pressure.

Depend where you are on the water companies supply pipe but the further you are away from the pump house the lower the water pressure. Equally demand from other users will effect your pressure. For instance if lots of new homes have been built near you in the last 9 months.

Demand in the early hours of the morning is low 2-3am and at that time you should have the highest pressure.

This is just a guess, but if the pressure is low at one tap say the bath then you may have a sticking washer on that tap, or a restriction in the feed pipe.

Maurice
December 2010