Its 150 wat WP 155, 11 years old, had to replace leaking tank last year, After that it started pulsing and never did find a solution. Now its not kicking in properly for the water downstairs, but upstairs it's still OK which seems odd. Tried bleeding the tank and altering the pressure switch screw but no change. Cannot understand why it works for upstairs but stopped on the ground floor, just a trickle from taps there.