What four numbers cover between them
Two hose bores, 32 mm and 38 mm, and two valve threads, 1½ inch and 2 inch. Between them they cover nearly every above-ground pool sold in Europe, and they cover it well: a 38 mm hose from one maker will push onto a 38 mm barb from another.
It fixes the envelope, which is what a fitting convention is for. Everything that connects to a pool — pump, filter, skimmer, inlet, solar collector, vacuum head — declares itself in one of these four numbers, and that declaration is what makes a catalogue comparable at all.
Why a bore says nothing about a hose
It does not promise a hose quality. Wall construction, spiral reinforcement, cold flexibility and UV resistance are all independent of bore, and a 38 mm hose that goes rigid at 8 °C is a 38 mm hose.
It does not promise that a stated size is a measured one. Nominal sizes are names; the actual outside diameter of a barb varies by a millimetre or so between makers, which is exactly the range in which a hose either seals or weeps.
And it does not promise that an adapter exists. Some assemblies step between the two families and some do not, and a page here reports the adapter as supplied, as sold separately, or as not mentioned — three different situations that a listing often blurs into one.
What has to be right besides the size
Wall thickness, on anything that passes through a pool wall — a skimmer cut for a steel wall does not seal against a frame pool’s liner, and the figure that separates them is a millimetre count the maker publishes. Gasket sets, because a thread that fits without the right gasket leaks. And clamp type on telescopic poles and vacuum heads, where the same logic runs on the dry side of the pool.
Everything on the circuit, and the poles too
Every family that carries water. Hoses and their fittings, pumps, filter systems, multiport valves, skimmers and inlet fittings on the circuit side; solar collectors, which tap into the same circuit and are the family where a bypass most often turns out to be needed; and vacuum heads, where the hose size decides which head a given pole and hose will drive.
What readers keep writing in to ask
Is 32 mm the same as 1¼ inch?
Close, and not the same. 1¼ inch is 31.75 mm, and the trade rounds it. In practice the parts are sold as a family and do fit each other; the caution is that a nominal thread size is not a measured diameter, and two parts described in different units are still worth checking against the maker’s own compatibility list.
Can I step 32 mm up to 38 mm?
With a published adapter, yes — most pump and filter makers sell one, and several include it. What does not work is forcing a hose onto a barb it was not cut for: it holds until it is under pressure, which is the worst moment for it to stop holding.
Does a wider hose move more water?
It adds less resistance, so a pump quoted at a given flow loses less of it. Whether that is worth anything depends on the pump: feeding 32 mm hose from a pump built for 38 mm throttles the pump, while fitting 38 mm hose to a 32 mm pump changes very little.
Why do valves use inches when hoses use millimetres?
Because the threads descend from imperial pipe sizes and the hoses do not. The 1½ inch and 2 inch threads on a multiport valve are plumbing sizes; the 32 mm and 38 mm barbs the hoses push onto are a pool-trade convention. The adapter between them is the point where the two systems meet.
Last reviewed 21 September 2026