Pop Up vs Pop Down Basin and Bath Wastes: What’s the Difference

Measure the basin or bath’s existing outlet before ordering a replacement, since a 32mm basin outlet and a 40mm bath outlet aren’t interchangeable without an adaptor. Where a product is listed as dual-rated for 32mm or 40mm, that flexibility covers most standard basins, but a bath almost always needs the full 40mm size.

• 32mm is the standard basin waste size. Some basin wastes are dual-rated for 32mm or 40mm outlets.
• 40mm is the standard bath waste size, and it’s not a like-for-like swap with a 32mm basin waste even if the cap style looks the same.

Trade tip: if replacing a waste rather than fitting a new basin or bath, take the old part with you or check the model’s spec sheet before ordering, since a mismatched thread size means the new waste won’t seat properly.