I have a question regarding water pressure. I do not get water pressure in the taps from the overhead tank which is 20 ft high at roof. However, when I run the mains line the pressure is too high.

Points to be noted:
1) There is one common line for filling and emptying the tank.
2) A check volve is installed at the start of the main line before pump so that the tank water does not reverse. This will allow only water to enter inside.

*** advise.

Regards,
Abhishek