How to replace a basin tap, even if the old one is seized

What you need

• Basin wrench with T-handle (10 and 11 mm box spanner)
• 17 mm open-ended spanner and an adjustable spanner
• Locking pliers
• Small hacksaw or oscillating multi-tool in case you have to cut
• Head torch, bucket and rags
• WD-40 penetrating oil
• Single-lever basin mixer with hoses and click-clack waste (Grohe Eurosmart, Tres Base, Roca L20 or Leroy Merlin / Bricodepot own brand, 35 to 120 €)
• Click-clack waste with or without overflow if the tap does not include one (8 to 15 €)
• New basin bottle trap with washers (6 to 10 €)
• 3/8 by 1/2 inch flexible hoses, 50 cm, if the supplied ones are short
• Silicone tap grease and cleaning vinegar

Step by step

1. 1

   Turn off the water and release the pressure

   Close both isolation valves under the basin fully and open the old tap until no more water comes out. If there are no valves or they will not close, shut off the mains stopcock for the flat. Put the bucket under the hoses.

2. 2

   Disconnect the hoses and the trap

   Loosen the hose nuts at the isolation valves with the 17 mm spanner, holding the valve with the adjustable spanner so it does not turn. Unscrew the trap nut at the waste by hand and move the trap aside.

3. 3

   Loosen the tap fixing nut

   Find the stud nut with its half-moon plate under the basin. Fit the basin wrench and turn anticlockwise with steady force. If it does not give, spray WD-40, wait 15 minutes, tap the nut gently with a screwdriver handle and try again.

4. 4

   If it is still seized, cut the stud

   Protect the ceramic with a wet rag. Cut the stud just above the nut with the hacksaw or the multi-tool. On old two-handle taps with a large brass nut, use a properly tightened adjustable spanner or a 22 or 24 mm box spanner, never a lever against the basin.

5. 5

   Remove the tap and the old waste

   Lift the tap out with the old hoses through the hole. Unscrew the waste nut from below and lift the waste out from above. Clean the limescale and old silicone from both holes with the plastic scraper and vinegar, and dry.

6. 6

   Fit the new waste

   Place the flat washer under the top flange of the waste, pass it through the hole and, from below, fit the conical washer and the nut. Line up the overflow slot in the waste with the basin overflow if there is one. Tighten by hand plus half a turn.

7. 7

   Fit the new tap

   Screw the hoses into the base of the tap by hand, fit the O-ring on the base, grease the fixing stud and pass everything through the hole. From below, fit the gasket, the half-moon plate and the nut, and tighten with the basin wrench while someone holds the tap straight. Stop as soon as it no longer turns.

8. 8

   Connect, open the water and check

   Screw the hoses onto the isolation valves, hot on the left, hand tight plus a quarter turn. Fit the trap with its new washers. Remove the aerator, open the isolation valves slowly, run for a minute and check hoses, base and trap with dry paper. Fill the basin, press the waste and check it empties without dripping.

Which basin tap to buy and what comes in the box

Modern basins have a 35 mm hole for a single-lever mixer; older two-handle basins have two or three holes (a deck-mounted tap or a three-piece set). If you are going from two handles to a single lever, you need a new basin or a hole cover plate, so check how many holes you have first. Measure the spout height too: a countertop basin needs a tall spout; an inset basin is fine with a 10 cm spout.

A single-lever basin mixer from Grohe (Eurosmart, Start), Tres (Base, Max), Roca (L20, Victoria) or the Leroy Merlin or Bricodepot own brand costs 35 to 120 € and comes with two 3/8 inch flexible hoses, the fixing stud with its half-moon plate and nut, and nearly always a click-clack pop-up waste. If your basin has an overflow (the hole in the front rim), buy a waste with overflow; if it has not, a waste without overflow, or water will seep out through the thread.

The key tool: the basin wrench. It is a long box spanner with a T-handle that reaches the 10 or 11 mm nut hidden between the basin and the wall. It costs 8 to 15 € and without it the nut is almost impossible to reach, especially on pedestal basins and vanity units with drawers.

The old tap is seized: freeing it without cracking the basin

With the hard water on the coast, the brass nut and the steel stud fuse together with limescale within ten years. First, penetrating oil: WD-40 or similar on the nut and stud, then wait 15 minutes. Tap the nut gently with the handle of a screwdriver so it vibrates and the oil works in. Try the basin wrench with steady pressure, no jerking.

If the whole stud turns with the nut, grip the stud from above with locking pliers on the end that shows inside the body of the tap (you have to remove the lever and the cartridge), or hold the tap from above with a rag and apply force from below. On old two-handle taps, each spindle has its own large brass nut: use an adjustable spanner with the jaws properly tightened or a 22 or 24 mm box spanner.

Last resort: cut. With a small hacksaw, an oscillating multi-tool with a metal blade or a Dremel, cut the stud just above the nut, protecting the ceramic with a wet rag. Never lever against the basin or knock the tap upwards: the ceramic cracks and a 40 € repair becomes a 150 € new basin.

Common mistakes when replacing a basin tap

The first is leaving the old waste in place. The pull rod of an old pop-up waste is linked to the tap by a lever; if you change only the tap, you are left with a hole behind it and a waste that will not close. Change both at once: the new click-clack waste closes with a push and needs no rod.

The second is tightening the fixing nut with all your strength. The basin is ceramic and the metal half-moon plate concentrates the pressure at one point. Tighten until the tap no longer turns and stop. The third is putting PTFE on the flexible hoses: they seal with the flat washer, and PTFE only crosses the thread. And the fourth, twisting the hose as you screw it on: hold the flexible part and turn only the nut.

One detail that gets forgotten: the trap. When you change the waste, the trap tail comes loose and its conical washer is usually deformed. Buy a new bottle trap (6 to 10 €) or at least the washers; it costs less than discovering a puddle in the vanity unit a week later.

• Plug the waste or put a rag in the bowl: the Allen screw from the lever drops into the trap.
• Hot on the left, cold on the right when connecting the hoses.
• Remove the aerator before you open the water for the first time and clean it after a minute of flow.

When to call a professional

Call us if the stud will not come out even after cutting, if the isolation valve leaks when you move it or will not close, if the basin is a pedestal and has to come off the wall to reach the nut, if the wall supplies are old iron, or if the tap you want to change is wall mounted and means working with eccentrics in the wall. Also if you are in a hurry: a seized tap can eat an entire afternoon.

Through our plumber service, replacing a basin tap costs 45 to 80 € in labour, including removing the old one even if it has to be cut, and fitting the new waste. We carry basin wrenches, hoses, isolation valves and traps in the van. We arrive in 20 to 45 minutes in Valencia, Alicante, Torrevieja and Benidorm. Fixed price on WhatsApp from a photo of the space under the basin, 6-month written guarantee and an invoice with IVA (VAT). More prices in how much a plumber charges.

Limescale and salt air: stopping the new tap from seizing

Before fitting the new tap, put a thin coat of silicone tap grease on the thread of the fixing stud and on the threads of the isolation valves. When it has to come off again in ten years, the nut will come loose by hand. If you live on the seafront (Torrevieja, Benidorm, Dénia, Santa Pola), choose a tap with a stainless steel finish or quality chrome: salt air pits cheap chrome in two summers.

Every three months, unscrew the aerator and leave it in vinegar for half an hour; it is the part that suffers most from the hard water in Alicante and Valencia. If the old tap only drips and you do not want to replace it yet, try how to fix a dripping tap first. And if it is the shower tap you are changing, the process is different: how to replace a wall-mounted shower or bath tap.