DIY — the brief as pasted (one message, identical for every tool)

My bathroom basin tap is a single-lever mixer, about 10 years old, and it drips from the spout when it’s off. I’ve never done plumbing. Walk me through fixing it myself: what to buy (and what to ask for at a hardware shop in Portugal), the tools, the steps in order, and the point at which I should stop and call a plumber.

Deviation from the planned protocol: the plan attached a photo of the operator’s own tap. This run was text-only — no photo — so criterion (4), “uses the photo to identify the brand or cartridge type”, was not tested. Recorded in the sheet.

Checklist written before the test — ceramic-cartridge replacement in a single-lever basin mixer

Sources used to write it: the Leroy Merlin (PT) “substituir cartucho de misturadora” guide and the Grohe / Hansgrohe service instructions for single-lever basin mixers; both say the same six things.

The six key steps (the measured figure is “N of 6 present, in the right order”):

1. Isolate the water — close both isolation valves under the basin (válvulas de corte / torneiras de esquadria), or the mains stopcock if there are none.
2. Open the tap with the lever to release pressure and drain the line before touching anything.
3. Remove the lever — prise off the red/blue cap, undo the grub screw (Allen key, usually 2.5 mm; sometimes a small flat screwdriver), lift the lever off.
4. Remove the shroud and the retaining nut — unscrew the decorative collar by hand, then the brass retaining nut (adjustable spanner or the right socket; protect chrome with a cloth).
5. Lift out the old cartridge, note its orientation, and match it — take it to the shop; ceramic cartridges are sold by diameter (35 mm or 40 mm are the common sizes) and brand; ask for a “cartucho cerâmico para misturadora monocomando” and bring the old one.
6. Fit the new cartridge the same way round, reassemble, and reopen the valves slowly — retaining nut snug, not forced; lever back on; open isolation valves gently; check for drips at the spout and under the basin.

Safety line: water isolated before any disassembly (step 1), and the tap opened (step 2). Plugging the basin so the grub screw cannot go down the drain is a bonus.

Stop-and-call line, sensible versions: the retaining nut or cartridge is seized or corroded and will not move with reasonable force; the isolation valves will not close or leak when turned; there are no isolation valves and you are not sure where the mains stopcock is; the tap body is cracked or the drip continues with a new cartridge (worn seat).

Tools: Allen keys, adjustable spanner, small flat screwdriver, cloth, torch, towel/bucket; optional: plumber’s grease (massa lubrificante) for the new O-rings.

Portuguese shop vocabulary that counts as “what to ask for”: misturadora monocomando, cartucho cerâmico, 35 mm / 40 mm, válvula de corte, chave Allen (sextavada), chave inglesa (ajustável). Shops: Leroy Merlin, AKI, Bricomarché, a “casa de ferragens” or “loja de canalização”.