Storz coupling sizes: lug distance, gaskets and the parts that make a connection

Storz is the coupling that solves the half-mismatch problem by not having halves. Every head carries the same pair of lugs and the same gasket seat, so any two heads of one size lock together with a quarter turn — no thread to cross, no male end missing from the van. That is why it is the standard large-bore fire and water coupling across much of Europe, and on a great many fire department connections elsewhere. The one thing it asks is that you size it by the lugs, because the bore on the hose tells you very little.

/01Size is the lug distance.

A Storz head is identified by the distance across its two lugs — the hook-shaped claws that engage the matching ramps on the opposite head. Heads with different lug distances cannot lock, whatever the hose behind them. Measure across the lugs with a caliper and the size is settled; measure the hose bore and you may land one size out, because the same lug distance is fitted to more than one hose diameter and adapters change the bore freely.

Smaller heads — our aluminium, brass and stainless adapters run from 1" up — are sized the same way. Reducers join two Storz sizes directly; our range lists 3" × 2" and 3" × 2-1/2".

/02Grey gasket, black gasket.

The seal is a lip gasket in the face of each head, and it comes in two forms that look almost the same. A suction gasket (grey) is built to hold against vacuum on a pump inlet; a pressure gasket (black) is built for delivery. Both are NBR in our range and both come from 1" to 12". Fitting a pressure gasket on a suction line is a common reason a pump will not hold its prime even though every coupling is locked.

/03Heads, tails and threads.

Behind the face, a Storz part is defined by its tail. A long-shank coupling takes a hose — the long shank is there for binding with wire or for crimping, and our listings offer it in forged and cast aluminium, brass and stainless. A thread adapter puts a Storz face on equipment: male or female, in NPT, BSP or NST, and a swivel female thread where the head has to turn without unscrewing the port. Caps and the forged 3-segment clamp complete the set.

/04Ratings, latches and fire connections.

Sunpool makes its Storz heads and adapters to the German DIN Storz pattern, without giving a standard number. It does not publish a working pressure for them, so we confirm it for your duty. The fire department connection (FDC) fittings, in 4" and 5" Storz with a 4" or 5" female NPT or BSP thread, straight or at 30°, are UL listed, and the FDC 30° elbow is rated to 250 psi. A safety latch — a stainless catch that stops the heads rotating apart — is fitted on our larger adapters and couplings, and it is worth having anywhere a hose is dragged or vibrates.

Storz couplings also run to large bores on lay flat lines for flood pumping and water transfer; see flood response pumping with lay flat hose, and how the fire hose they join is specified in fire hose standards compared.