Replacing the angle stop valve under a sink yourself

What you need before you start

Most flats built from the 1970s onward have an angle valve on the riser supplying each tap and toilet, usually a quarter-turn chrome fitting with a small lever or a slotted spindle. Older buildings and some 1930s wooden houses in Kalamaja or Nõmme may only have a stopcock further back, which changes your isolation point but not the rest of the job.

You will need an adjustable spanner, a basin wrench if the valve sits somewhere your hand cannot reach, PTFE tape or hemp and jointing compound, a bucket or basin, an old towel, and the new valve itself. Buy a compression valve in the same size as the existing pipe, normally 15 mm for a copper riser in a flat.

Check the new valve has the right outlet thread for what you are connecting, usually a 1/2 inch flexible tap connector or a toilet fill hose. If you are unsure of the size, take the old valve to a plumbing merchant and match it rather than guessing.

How to isolate the water without touching the riser

Start by turning the angle valve itself clockwise to see if it still closes. If it turns freely and the drip or flow stops, you have your isolation and do not need to go near the riser or the flat's main stopcock at all.

If the valve is seized, work it gently with a few drops of penetrating oil and light, repeated pressure rather than force. A valve that has not moved in years can snap its spindle if you lean on it with a spanner, which turns a simple job into a bigger one.

If it will not budge after reasonable effort, the next isolation point is the riser's own shut-off, often in a cupboard, a service duct, or at the water meter, or failing that the main stopcock for the flat. Turn it off, then open the tap above the valve to relieve pressure and confirm the water is genuinely off before you go further.

Taking off the old valve

With the water off, place a bucket underneath and open the tap or flush the cistern to drop the remaining pressure in the line. Loosen the compression nut connecting the valve to the pipe with an adjustable spanner, holding the pipe steady with a second spanner so you do not twist it.

Disconnect the flexible hose or fill pipe from the valve's outlet side next, catching the last of the water in the bucket. Old olives, the small brass rings inside compression joints, sometimes stay stuck on the pipe or seize into the fitting.

Once both connections are free, the valve should slide off the pipe end. If it is corroded onto the copper and will not move by hand, stop rather than forcing it — that is covered further down.

Fitting the new valve

Wipe the pipe end clean and check it is round and undamaged where the new olive will sit; a scored or oval pipe end will never seal properly under a compression joint. If the existing pipe end looks poor, cutting back a centimetre or two with a pipe cutter gives you a clean surface to work with.

Slide the new compression nut and olive onto the pipe, then the valve body, and tighten the nut by hand before finishing with a spanner, generally three-quarters of a turn past hand-tight rather than as much as you can manage. Overtightening a compression joint is at least as common a cause of leaks as undertightening.

Wrap PTFE tape clockwise round the outlet thread and reconnect the flexible hose or fill pipe, then turn the water back on slowly and check every joint by eye and by hand for a good ten minutes before considering the job finished.

• Adjustable spanner and a second spanner or basin wrench
• New compression valve matching the existing pipe size
• PTFE tape or hemp and jointing compound
• Bucket, old towel, and a torch for cupboards under the sink
• Pipe cutter, only if the existing pipe end needs recutting

The mistake almost everyone makes

The most common error is skipping the isolation check and assuming the valve you are removing is also the only thing holding back the water, then finding out otherwise with the pipe open. Always confirm the water is off at your chosen point, by opening a tap, before you loosen anything.

The second is overtightening the compression nut to compensate for a joint that will not stop weeping, which usually means the olive is misaligned or the pipe end is damaged rather than the nut being loose. Backing off, checking the olive sits square, and retightening properly solves more leaks than brute force ever does.

When to stop and call a plumber

A valve that will not turn, will not come off the pipe, or that snaps its spindle under gentle pressure is telling you the fitting has corroded onto the copper. At that point the safe move is to isolate further back and stop, rather than risk cracking the pipe itself inside a wall or floor void.

The same applies if the shut-off point you find is itself seized, if there is any sign of a leak inside a wall or ceiling void, or if the pipework is older galvanised steel rather than copper, which behaves differently under a spanner. These are jobs where the fix depends on what you find once the old fitting is off, which is hard to plan for in advance.

For that kind of situation, or simply if you would rather not spend a Saturday under a sink, plumbing work from us starts at 45 € per hour, and general odd jobs from 39 € per hour if it turns out to be more a matter of access or carpentry than plumbing.