Size Guide – Camping & Caravan Direct

A size guide is one of those things you rarely think about until you need it. Whether you are replacing a worn part, matching a fitting or checking that a new accessory will work with your setup, getting the measurements right first time saves a return, a refund and another weekend spent waiting for the post.

Why measurements matter

Caravan and camping equipment uses a mix of imperial and metric fittings, and the two do not always line up neatly. A part described as 1½ inches is not the same as a 1½ inch hose measured across its outside diameter, and a sink waste listed with two sizes is usually quoting both the pipe connection and the thread.

Checking the actual dimensions of the item you are replacing is always more reliable than assuming a like-for-like swap will fit.

Common fittings and what the numbers mean

Plugs and bungs. A replacement plug sized at 1½ inches refers to the nominal pipe size it is designed to seat into, not the width of the plug itself. Measure the internal diameter of the housing it fits.

Sink wastes. A fitting marked 1¼ inches to ¾ inches typically connects a 1¼ inch waste pipe to a ¾ inch threaded outlet. The first figure is the pipe size, the second the thread.

Hose nozzles. A nozzle described as ½ inch BSP male with a 10mm hose tail has a threaded end to British Standard Pipe sizing and a barbed end for 10mm internal diameter hose. BSP sizes refer to the thread, not the outer measurement of the fitting.

Liquid treatments. Toilet additives are commonly sold in one-litre bottles, often as a twin pack containing both a blue and a pink formulation for the waste and flush tanks respectively.

A practical approach

Before ordering, take the old part with you if you can, or measure it in place with a rule or caliper. Note both the thread size and the pipe size where a component has two. If a listing quotes a single figure, it is usually the pipe or hose size rather than the thread.

Where a product is offered in several sizes, the smallest and largest are the ones most often confused, so it is worth double-checking which end of the range you need.

Keeping spares on hand

Small fittings are inexpensive and awkward to source at short notice, particularly mid-trip. Carrying a spare plug, a length of hose and a couple of washers costs very little and can rescue a weekend. It is also worth noting the sizes you use most often somewhere in the caravan, so a replacement can be picked up without a second trip to measure.