Hi, I need advice.
Having fitted a new bath and basin I now have low pressure/flow in the hot tap basin.
Also, the bath taps are a shower mixer and as the cold water is mains fed the water will not mix in the shower (at shower height).
Would it work if I fitted a pump, say 1.5 bar to the hot water pipe before both bath and basin and a non return/ double check valve after the pump and a pressure reducing valve to the cold feed?
I phoned a really unhelpful plumber who told me I had the wrong taps and didn't know what I was doing!
I spoke to salamander 'pumpwise' but they recommended a pump that costs about £300!
By fitting a 1.5 single pump and reducing the mains pressure, if need be, I was hoping it would even out the pressures at the taps. Then I could fit an NRV to both to prevent cold flowing back into the pump or hot to the cold.
Whilst it sounds as if the plumber you consulted was less than sympathetic I'm afraid he's probably correct. I'll bet you have 1/4 turn ceramic disc taps and the basin is a monobloc (with those dreadful 7mm restricted tails). Your restrictions on the BSM is discs plus tails plus the diverter.
If you used standard isolating valves to comply with water regs these are also restrictive and should be full bore. I'm presuming you also fitted a non return vv on the BSM hose if it didn't come with one which is also restrictive.
The main problem is not pressure its flow rate with the restrictions imposed as above.
There is, however, a possibility of a pressure problem if you've used those nice up and over U shaped taps which do affect pressure because of reduced static head.
I'd suggest you run a cold feed from the CWST (so both hot and cold will be at same pressure) use a pump and pump BOTH hot and cold because as already mentioned it will be virtually impossible to get them balanced properly with pumped hot and mains cold. Even if you do achieve it then all the water board has to do is change the mains pressure even slightly and they'll be unbalanced again.
If you don't fancy that little lot then perhaps you should look at changing the taps.