What decides whether it goes well
Three measurements taken beforehand: tap hole diameter, tail length to the valves, and worktop thickness. All three are covered in the measuring page, and all three are cheaper to take than to discover.
The one tool with no substitute
A basin wrench. The back nut that holds a tap down sits in a space you cannot see and cannot get a normal spanner to, and the tool exists for exactly that geometry. Everything else in the job can be done with water pump pliers.
One rule with those pliers: serrated jaws mark chrome permanently. A cloth around a visible nut costs nothing.
The shape of the job
Close both isolating valves and open the tap to prove they closed. Disconnect the flexible hoses at the valves — expect a little water in them. Undo the back nut, lift the old tap out, clean the surface it sat on. Set the new tap with its washer, tighten the fixing from below, connect the hoses, open the valves slowly and watch every joint for a minute.
Two things worth replacing while you are there
The flexible hoses. They are a consumable, they cost a few euros, and they are the part that fails messily. A hose fitted with a gentle curve rather than pulled taut lasts far longer.
The isolating valves themselves, upgraded to double-outlet if a filter tap or a bidet seat might follow. The job is the same either way, and doing it twice is not.
Where this page stops
Nothing here replaces the tap’s own installation instructions, and nothing here covers work upstream of the isolating valves. If a valve will not close, or an outlet thread will not turn cleanly, the job has changed into one that needs the supply off further back — and that is the point to stop.
Questions people actually ask
Do the flexible hoses need PTFE tape?
Not on the union nuts, which seal on a rubber washer. Tape belongs on tapered threads; the hose maker states which of its ends is which, and putting tape where it does not belong makes the joint harder to tighten rather than tighter.
How tight is tight enough?
Hand tight plus a small amount with a tool, on any joint that seals on a washer or an O-ring. Overtightening splits plastic nuts and crushes washers, and a crushed washer leaks worse than a loose one.
Last reviewed 5 September 2026
