No hot water at one tap but cold is fine
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Most likely cause & what to check
Check if the problem is the tap or the hot supply. Remove the spout aerator (unscrew the small mesh filter at the tip of the spout) and check if flow is restricted — limescale can block the aerator on the hot side only.
Check the isolation valve for the hot supply to this tap — it's usually under the sink or basin. Make sure it's fully open (slot parallel with the pipe).
If this is the only tap with no hot water, and all others in the house work fine, the fault is specific to this tap or its hot water branch pipe.
For a thermostatic mixer tap, the thermostatic cartridge may have failed or stuck. These cartridges have a maximum temperature limiter — if it's been turned down fully, the hot supply is blocked. Check the temperature limiter setting on the cartridge.
For a single lever monobloc tap, the ceramic cartridge inside may have failed — the hot pathway through the cartridge is blocked. Replacing the cartridge (brand-specific, £10–£40) is usually straightforward.
If there's no hot water at multiple points in a bathroom or kitchen, the fault is in the hot supply branch — there may be a partly closed isolation valve or a blockage in the section of pipework serving that area.
In hard water areas, limescale can eventually block the inside of copper pipes, especially old small-bore pipework. A plumber can descale or replace the affected section.
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