I had two separate taps on my sink in the kitchen and decided to buy a mixer tap due to the other taps snagging on things when I was filling buckets up etc. The old taps worked fine with decent pressure hot and cold. Mains cold and a gravity fed hot water system. I just installed the flexi hoses straight to the bottom of the taps, on the feeds not really a hard job! But both the cold and the hot water have now considerably less water pressure! I can’t work out what it could be other than a faulty tap? I can’t see any blockage or anything and as said above no soldering or anything was done no extar joints pipes or anything, just a simple reconnect of two hoses for the feeds.

Have you read the box? Some say for low pressure systems only i.e. not a water tank in the loft (if that is what you have). I’ve had the same although the cold keeps a decent pressure, the hot is useless.

you are confusing water pressure and flow rate, something i’ve heard lots of plumbers do, two separate things. the flexi’s have a thinner internal bore than the old fittings, so less water is coming through at the same pressure, not the same water coming through at less pressure.

If the tap has a removable tip on the nozzle unscrew it and check for an airator. If so try removing the insert. I had to do it on my bath taps as it was taking too long to run a bath.

remove the grey bit

How to install or replace a clean faucet aerator

from wikipedia

A faucet aerator (or tap aereator) is often found at the tip of modern indoor water faucets. Without an aerator, water usually flows out of a faucet as one big stream. An aerator spreads this stream into many little droplets. This helps save water and reduce splashing.
Faucet aerators are often used in homes with low water pressure in order to increase the perceived water pressure.[1]

Andy

Yea I have removed the plastic nozzle he taps were new. I have not touched the pipe work its exactly the same flexi hoses that were on before with the old taps etc I just swapped over the single taps for a two hole, mixer Its not a low pressure tap too I don’t think. Normally its the hot water on mixer taps when you install them I have heard but the cold pressure as gone down a real lot too so I just presume its the tap.

in that case its the size of the internal design of the tap, restricting the flow, often the actual body of the mono tap means that they are machined smaller inside. could be faulty tho, i fitted a faulty elbow once that didnt allow any water to flow thru, due to not being machined properly

I have stripped said tap down and removed some ceramic valves from the working single taps and fitted them but still exactly the same outcome 🙁 I have taken the neck off both the tap ans stuck some wire with rubber coating all along the body then flushed it out with hose pipe! still its the same so just as to be the design. I can see how there could be any other faults. The tap body is a little narrower than the old single taps but surely not enough to to knock at least half the pressure at the spout!

DOes the tap open just a quarter or half turn? The old ones all the way around? That was the difference when I changed mine.

no there both quarter turn ceramic valves.

Have you measured the flow rate of the pipes (without tap)

and the flow rate with the tap attached.

My guess is that this is just a new water saving tap, in the same way that just about all new toilet cisterns are now water saving. I noticed the same thing on our new kitchen taps a year ago, but we just got used to it running slower.