Finding a tap set genuinely capable of operating at very low pressure is your only hope without installing a pump. If anyone's had a similar problem perhaps you could advise? Am I on the right lines... or getting a bit carried away? I don't want to fit the new tap only to find the flow is still poor. I'd also like to exhaust all other options before fitting a pump on the whole hot water system.

The larger two of these holes are for the feed pipes to be screwed in and the smaller two are where the threaded connection bars are screwed into. These threaded bars should be fitted before dropping the tap through the hole in the basin. Only do them up as tight as you can by hand. If you use pliers or grips there is a danger you will damage the thread. The image above shows the tap at the top with the connection tails at the bottom ready to receive the hot and cold feeds. The 10mm feed pipes screw into the underside of the tap and are then machined out to become 15mm copper tails ready for the connection of 15mm feeds. With the washer in place the nuts can now be tightened onto the threaded bar and this is where the DIY enthusiast struggles. Use a Box Spanner If your basin is designed for a monobloc tap, it will have a single tap hole, so you don't have the option to convert to separate taps unless you change the basin.

£29.30 RRP

There is hardly any room under the basin, less under a bath and a kitchen sink is a nightmare! Plumbers on the other hand, carry a box spanner which is a long open tube with the correct size nut shaped hole at the end. Copper tails, which are narrower where they go through the tail, increasing to 15 mm at the pipework connection end. Less restrictive than flexis, but no as good as 15 mm pipes. I have very low hot water pressure in my upstairs basin mixer tap. Being in a maisonette there is hardly any head height from the tank (about 0.8 metres). However there is decent enough flow from the bath tap (separate hot & cold taps) which only slightly lower (a further 0.4 metres). This has led me to conclude that whoever fitted the tap probably didn't choose one suitable for a low pressure system. Ceramic insert (1/4 turn) taps have two ceramic discs inside, each with two diametrically opposed slots. The faces of the discs are grounds extremely flat so that they form a water tight seal. The slots each occupy just under 1/4 of the diameter of each disc, a little way in from the outside. When closed, the slots in the upper disc are covered by the unslotted portion of the lower disc, and no water flows. When open the slots of the upper and lower discs are in alignment, so water can flow through. However, the area through which the water can flow is much less than that offered by a traditional tap washer being raised off its flat seating, so flow rate is less. The minimum pressure tap I have been able to find is 0.1 bar. It has M10 connections and the flexi tails included - but they look like they will still be restricting flow somewhat as the aperture of the tails is pretty small especially at the compression nut end. So I have been considering using some copper tap tails instead. I have also been searching for a monobloc mixer tap which has larger M12 connections for the best chance of maximising flow, however, I've not been able to find any... in fact you practically never ever see thread size included in specs!!

It is slid over the thread and the other end twisted tight by putting a nail or something similar into the hole and turning. Easy! Once the tap is in the hole with the flat washer or mounting plate placed over the threaded bars, the steel washer can be slid into place also.