I'm a DIYer who does plumbing once in a blue moon. I ordered flexible tails to connect the bath filler, and the bidet mixer comes with them included. Here is the puzzle, why have I installed 22mm copper tube to feed the bath, when the bore of the tail is only 13mm? Similarly, the basin has 15mm pipes but the tails and mini valves have a bore of around 8mm. I wonder if the fittings had clear bores designed into them, we could all use smaller pipe? Or is it me? Copper is very expensive at present due partly to increased demand. Smaller pipe would use less metal, and be greener due to less energy used in production and carriage.

There is an increasing proliferation of imported taps which are best suited to mains pressure systems. If you have a gravity fed system then buy new taps or you may find that the flow is disappointing.

The above comments are on the right lines. Britain has traditionally used a tank system for domestic water to prevent back syphonage and contamination. Hence low pressure = 22mm for baths. The Victorians led the way in public water and sewerage and were paranoid about eg cholera infections being spread between households via plumbing. Continentals favour high pressure direct mains systems and hence small bore. Small bore tails will significantly reduce flow rates.

Flexible tails are not as robust as hard soldered. The trick with the latter is to fit a 22mm tail of 6 inches before fixing the bath (15mm for basins) and then plumb to it.