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A badly chosen coupling means a leak, lost flow or a part that simply will not fit. Guillemin, Storz, DSP, Keyser, cam-lock, Clamp, DIN and SMS systems sometimes look alike, but they are not interchangeable: this guide shows you how to recognise them and match them correctly.
Two families: symmetrical and male / female couplings
First thing to do: check whether the two halves of the coupling are identical. In a symmetrical coupling, both half-couplings are alike: there is no male or female, you bring them face to face and lock them. This is the principle of Guillemin and Storz couplings, very handy in the field because any length of hose connects to any other of the same system. In a male / female system, such as cam-lock couplings, one part slides into the other and levers lock it.
The coupling is then connected to the hose (hose tail and clamp, or screw-on fitting) and to the pump (thread). The same system can therefore exist with several end types: this is the second thing to identify before ordering.
Recognising each system
| System | Principle | Common uses |
|---|---|---|
| Guillemin | Symmetrical: two identical half-couplings, locked by their lugs | Water transfer, worksites, irrigation, depending on the model |
| Storz | Symmetrical claw type: the two halves join with a quick turning movement | Fire fighting, engine-driven pumps, discharge lines |
| DSP | Symmetrical locking system, widespread in French fire-fighting equipment | Fire equipment, water intakes |
| Keyser | Specific system, to be identified from your existing equipment and the product page | Networks and equipment already fitted with Keyser |
| Cam-lock (Camlock) | Male / female: the male adapter slides into the female coupler and two levers lock it | Liquid transfer, tankers, industry, depending on material and gasket |
| Clamp | Two flanged ends tightened by a clamp, with a gasket between them | Food, brewing, frequent dismantling for cleaning |
| DIN | Family of couplings defined by DIN standards: the exact standard is given on the product page | Industry and food, depending on the model |
| SMS | Sanitary stainless steel coupling with a nut | Food processing, drinks, dairy, depending on the model |
These descriptions are deliberately general: exact diameters, threads, materials and gaskets are always given on each product page.
Diameters, threads and gaskets: the three checks
- Diameter: read the marking on the coupling or the product page. The coupling diameter and the hose inside diameter are not always the same value: for a hose tail, it is the hose inside diameter that matters. Always compare with the product page.
- Thread: on the pump, tank or valve side, the BSP (gas) thread is the most common. A male thread screws into a female thread of the same type and diameter; never force two different threads together.
- Gasket: a flat gasket sits inside the coupling and ensures the seal. Replace it if it is hardened, crushed or cracked, and choose a material suited to the liquid (water, hydrocarbons, chemicals): the product page tells you.
Matching two different systems
Two different systems do not connect directly. You need an adapter designed for that combination (check the product page for the pairing offered), or fit both ends with the same system. Each adapter adds a gasket and therefore a possible leak point: if you connect often, it is better to equip the whole setup with a single system.
For fire fighting, the choice of system depends on the regulations applying to your site: see the guide /en/content/19-choose-a-fire-fighting-engine-driven-pump and follow the manufacturer’s instructions as well as the requirements of your insurer or fire service.
The mistake to avoid: trusting appearances
Two symmetrical couplings that look alike, or have the same nominal diameter, are not necessarily compatible. Never force a lock that will not engage: you damage the gasket and the coupling, and the leak shows up when you pressurise. Always compare the system and the diameter with the product page before ordering.
Method: choosing your coupling in 5 steps
- Identify the system on your existing equipment: identical halves or male / female, claws, levers, nut, clamp.
- Note the diameter marked on the coupling, or measure the hose inside diameter for a hose tail.
- Choose the end type: hose tail with clamp, or male or female threaded end depending on the pump or valve.
- Choose the material and gasket according to the liquid, pressure and temperature given on the product page.
- Check the whole setup: add the adapters you need and check for leaks the first time you fill the line.
Frequently asked questions
Can a Guillemin coupling be connected to a Storz coupling?
Not directly: they are two distinct systems. You need an adapter designed for that combination, or fit both ends with the same system. Check compatibility on the product page.
How do I know which coupling diameter to order?
Read the marking on the existing coupling, or measure the hose inside diameter if it is a hose tail. Do not work it out from the outside of the hose. If in doubt, contact us with a photo of your equipment.
Do I need to change the gasket every time I dismantle?
Not necessarily: inspect it. Replace it if it is crushed, hardened, cracked or swollen, and keep spare gaskets in the right material for the liquid you handle.