Low water pressure from gravity fed water tank

[goldridgeg]

Hello,

We moved into a new build, double storey townhouse about 6 months ago. The gravity fed water tank was overfilling out the roof due to a faulty ball valve.

The building plumber repaired this fault, but since then the cold water to the basin, bath and power shower has been about 10 % what it was. I checked all the taps and valves were reopened in the loft. I assume it is not a blockage at the taps, as all the outlets have poor pressure

Any ideas please as to what the problem is and how I rectify it?

[stoneyboy]

goldridgeg,
Assuming the only work that was carried out was replacement of the ball valve it may be that the full water level in the tank has been set too low.
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