One module, two sizes – the adapter determines the size

Rule of thumb

With GF iFIT one elbow, tee or coupling module fits d16 and d20, a second one d25 and d32. Which pipe size is connected is decided solely by the adapter that goes onto the pipe. That is why modules are counted per fitting and adapters per pipe end – and tools per size.

Where does the rule come from?

From the design of the system: with iFIT, GF separates the fittings (modules in PPSU) from the joining technology (adapters with toothed ring, O-rings and inspection window). The delivery programme therefore lists the modules as “16/20” and “25/32” and the adapters per size 16, 20, 25 and 32. An earlier version of this rule read “One tool set, all sizes” – according to the delivery programme that is not true: chamfering and calibrating tools exist per size (decision E-ST2-1, 17.10.2026).

What is technically correct?

The module has a socket at each connection into which the adapter snaps; the adapter carries the parts that hold and seal the pipe and must therefore match the pipe size. A tee module 16/20 can thus take d16 on one outlet and d20 on the other two – depending on the adapter. For the parts list this means: one module per fitting, one adapter of the right size per pipe end at the module. A branch with three pipe connections therefore needs one tee module and three adapters. The change between module sizes is made with the reducing module 16/20–25/32.

Where does the rule end?

• It applies to the system’s modules. Transition, fixture and radiator connection modules have fixed dimensions on the thread or fixture side.
• Tools are size-bound: chamfering tool per size, tool set for 16/20 or 25/32.
• The adapter is destroyed when undone; the module is reusable according to GF – spare adapters therefore belong in every parts list.
• Other push-fit systems may be built differently; the rule is a property of iFIT, not a general principle.

What does the standard say?

No standard governs how a manufacturer divides up its modular kit. The assignment of module to size is the manufacturer’s design and is stated in the delivery programme; the system is approved as a whole with its own pipes (manufacturer data).

DIN/EN versus ASME/ASTM

There is no counterpart in the ASME/ASTM world: there, fittings – including push-fit fittings – are made per nominal size. The modular idea with a separate adapter is a manufacturer’s system solution, independent of the standards world.

Worked example

For an additional tap, a branch is taken from a d20 line and continued in d16. Needed are a tee module 16/20 with two adapters 20 and one adapter 16, two elbow modules 16/20 with two adapters 16 each, and at the end a fixture connection module with one adapter 16 – in total four modules, two adapters 20 and six adapters 16, plus two spare adapters. Anyone who counts only the fittings arrives with four parts and cannot connect anything.

Zickwolff reference

The parts list tool calculates exactly this way: modules per fitting, adapters per pipe end and size, spare adapters and, on request, the tool set for the size. Everything from stock, also individually packed.

Checked today

Verdict: applies (class A). The rule follows the delivery programme and the design of the system.

Further reading

• GF iFIT: push-fit system d16–d32 for polybutene and multilayer pipe – tool-free, detachable – GF iFIT in the press systems pillar