We have two bathrooms divided from a single bathroom.We have them attached t a single 1000 little water tank.. since the pressure in bathroom 1 was OK it was very bad pressure in bathroom 2.So we installed a pressure pump which is quite good.My question is in absence of electricity there is NO pressure in bathroom 2.. what should I do.?

I am going to guess that the booster pump does not allow water to flow through when it's off (no electricity). I am also guessing that having no electricity is an infrequent situation for you. But if it is too much of a headache, then you might want to try putting in a bypass around the booster that you could engage during times with no electrical service.