UK trade guideBathroom Spares 3 min readUpdated 9 July 2026

How to Fit a Basin Bottle Trap (UK)

Install a 1 1/4" bottle trap or P-trap on a basin waste. Compact chrome and Marley plastic options.

McAlpineMarleyWirquin

Choose the profile

Bottle trap — compact, visible under vanity units. P-trap — cheaper, hidden inside cabinet. Both provide 50 mm water seal.

Fit

Basin waste 1 1/4" thread — trap hand-tight to compression olive. 40 mm waste out to soil stack.

Frequently asked questions

Why does the basin drain smell?
Trap seal has evaporated (typical after 3+ weeks unused) or self-siphoned. Run water to refill. If persistent, fit an air admittance valve (Durgo).
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