Kitchen tap rocking or loose — how to tighten it

A kitchen mixer tap that rocks or moves is held by a single backnut underneath the sink. Over time, this nut can loosen due to vibration, temperature cycles, or simply never being tightened sufficiently on installation.

Turn off the supply at the isolation valves under the sink. No need to drain anything — just isolating the supply is sufficient.

Reach under the sink with a torch. Look up at the underside of the tap body — you will see two flexible supply hoses and, between or around them, a backnut (a large plastic or brass nut threaded onto the tail of the tap).

If the nut is accessible, tighten it clockwise by hand as far as possible, then use an adjustable spanner to snug it up. Take care not to over-tighten — the tap body (often plastic internally) can crack. A firm tightening with one hand is usually sufficient.

If the nut is in an awkward position: a basin wrench (a long-handled tool with a swivelling jaw specifically designed for reaching backnut in confined spaces under sinks, £15–£25) makes this job much easier.

After tightening, restore the supply and check the tap body is now completely stable. If it still moves, check whether the worktop hole is oversized — a thin rubber or plastic stabilising plate between the tap base and worktop can take up any slop.