We have put in new hot water heater all line out have no pressure new place in home center of house took out gas water heater out how do I fix low pressure problem

Did you sweat the copper adapters while they were on the water heater.. If so, that could have melted the diptube and diptube will need to be replaced.

Let's start at the water heater drain first. Hook a hose onto the drain and then when you open the drain at the bottom of the water heater all the way.. do you have a good solid pressurized stream of water.. If you do, then problem is going to be at the hot water outlet.

If you don't have full pressure... problem is at the cold water dip tube of heater OR at the cold water shutoff going into the heater...

Investigate what I suggested and then get back to us with answers... MARK

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