Press-Fitting Jaw Profiles (TH / U / F / M): Tool Compatibility Explained

What a “jaw profile” actually is — and why the wrong one fails silently

A press-fitting jaw profile is the shape stamped into the tool jaw (or press ring) that closes around the fitting sleeve and squeezes it onto the pipe. The letters — TH, U, F, H, M, V — describe the geometry of that contour: where the jaw contacts the sleeve, how many compression bands it forms, and where the load is concentrated relative to the O-ring underneath. It sounds like a small detail. On a job site it is the difference between a joint you can warrant and a callback you pay for out of pocket.

Here is the part every fitting manufacturer and independent tooling guide agrees on, and the single most important sentence in this article: the correct jaw profile is determined by the fitting manufacturer, not by the installer. Each fitting is designed and tested with one specific pressing contour, and the certification approval is tied to that contour. Mix a TH fitting with a U jaw of the same diameter and the tool will still close — that is the trap. The visible crimp can look acceptable while the O-ring is compressed unevenly, the sleeve is deformed in the wrong plane, and the joint no longer matches the geometry it was leak-tested to. It may hold at commissioning pressure and weep six months later behind a finished wall. There is no field method to “check” a mis-profiled press after the fact; the only defence is matching the contour before you pull the trigger.

That is why “will these fittings work with my press tool?” is really two questions. First: does my tool accept a jaw or ring in the profile this fitting requires? Almost always yes. Second: is that jaw sized for this exact diameter? Also usually yes, once you own the set. The profile question is the one that decides warranty; the diameter question decides whether today’s install can happen. Get both right and the brand on the fitting is your choice, not your tool’s.

TH, U, F, M: which profile belongs to which system

The four profiles a multilayer and mixed-material contractor meets most often each carry a lineage. Knowing that lineage tells you instantly whether a fitting will fit the jaws already in your case.

TH profile is the most widely adopted composite-pipe contour in Europe. It is used across a long list of multilayer systems — Viega, Wavin, Unipipe/Unicor, Henco, Comap/Purmo and Tiemme among them. If your crew already presses multilayer PEX-AL-PEX from a European brand, there is a strong chance TH jaws are already in the kit. TH’s breadth is precisely why it is the safest default to standardise around for a mixed fleet of installers.

U profile is associated with Uponor and its compatible lines (Unicor Unipipe, Wavin Tigris, Coes). U-profile jaws are made for the mainstream tool bodies — Ridgid, REMS, Klauke, Novopress — so a contractor moving between an Uponor-spec job and a general multilayer job usually only swaps the jaw, not the gun. If your radiant-heating work leans on Uponor-style systems, U is the contour to confirm on any new fitting supplier.

F profile (F-contour) originates with Fränkische’s alpex multilayer system. It matters here for one genuinely useful reason: Fränkische’s own alpex-duo XS fittings are engineered to be pressed with both F- and TH-contours using conventional certified press tools. That is a rare, manufacturer-stated dual approval, and it is worth knowing because it shows contour flexibility is designed in at the fitting, never improvised at the jaw. Do not read it as licence to cross profiles freely — it is an approval that exists only because that specific fitting was tested for it.

M profile lives in a different material world. M is the system-independent contour for metal press systems — copper, stainless steel and carbon steel — used by brands such as Geberit, Sanha and Conex Bänninger’s >B< Press, and by drinking-water metal fittings governed by DVGW worksheet W 534. Because M is system-independent, any M-contour fitting can be pressed with any M-contour jaw. That is the exact opposite of the composite world, and the reason you must never assume a plastic-composite habit carries over to metal. V profile is the parallel copper contour (Viega Profipress and similar), used for copper and some gas and heating lines.

The compatibility table contractors actually need

This is the reference to keep on the van. It maps each profile to the pipe world it belongs to, the systems it is associated with, and the practical rule. Treat the “associated systems” column as a lineage guide, not a licence — always confirm the specific fitting’s approved contour on its own data sheet before you press.

Read the table with one discipline in mind: the columns for composite (TH/U/F/H) and metal (M/V) never bleed into each other. A crew that has pressed copper with M jaws for a decade will instinctively “just press” a multilayer fitting — and that instinct is exactly how a mis-profiled joint gets into a wall. Composite fittings for water and radiant heating that Hitze supplies are built to EN ISO 21003-3, the fittings part of the multilayer piping standard, and the pressing contour on the fitting is what carries that approval into the field.

Your press gun is not the lock-in — the jaw is

The most expensive misconception in press systems is that changing fitting brands means buying a new tool. For the overwhelming majority of contractors, it does not. The major press-tool platforms — Novopress, REMS, Klauke, Ridgid and Milwaukee — are built around interchangeable jaws and press rings. The gun supplies the force; the jaw supplies the contour. Change the jaw, and the same battery-powered body that pressed one brand yesterday presses another today, provided the jaw matches both the profile and the diameter of the fitting.

That has a direct commercial consequence. A distributor or a fit-out contractor who has been paying a premium to a single brand — often a Viega or Uponor system — because “the crew’s tools only take those fittings” is usually mistaken. The tools take the profile. If a comparably certified fitting is available in that same TH or U contour, the switch costs a set of jaws, not a fleet of guns. That is the entire economic argument for standardising on a full-range supplier: you keep every press gun on the truck and change only the consumable at the tip.

There is one honest caveat. A handful of manufacturers ship proprietary or “system” jaws intended to keep their fittings and tools paired — some Viega Smartpress and Uponor S-Press setups lean this way. Where that is the case, you either buy the matching jaw or you spec a fitting in an open contour that your existing jaws already cover. Hitze deliberately sits on the open side of that line: its press fittings are made in the mainstream TH, U, F and M contours precisely so a trade buyer never has to re-tool a crew to adopt them. If your team already presses multilayer, you almost certainly already own the jaw that presses a Hitze fitting.

How a Hitze press fitting is built and what gets checked

Compatibility is only half the story; the other half is whether the fitting you press to the correct contour actually holds. A Hitze multilayer press fitting is a three-element joint: a lead-free brass bore that carries the water, a stainless-steel press sleeve that grips the pipe, and a twin O-ring seal seated where the sleeve compresses. The brass is drawn from dezincification-resistant and lead-free grades — CW724R, CW511L and CW602N (DZR), with CW617N where a standard grade is specified — so the wetted metal both seals and stays safe for potable water. The stainless sleeve is what your jaw closes on; its geometry is matched to the TH, U, F or M contour the fitting is offered in.

On the process side, Hitze — a German brand producing piping systems since 1974 from a 120,000 m² base with 1,000+ employees, exporting to 118+ countries — designs the sleeve-and-O-ring geometry around the target contour and then verifies the pressed joint rather than assuming it. Finished fittings and pipe move through rows of pressure-test benches — hydrostatic verification against DIN and EN ISO requirements, checking leak-tightness of the pressed connection under sustained load, not just a quick pass at commissioning pressure. The multilayer pipe those fittings press onto is built to DIN 4726 with an oxygen-barrier layer, and the composite fitting system follows EN ISO 21003. Where a market needs it, Hitze holds German and international potable-water approvals — SKZ testing, DVGW type examination, UK WRAS material approval and an NSF / BS 6920 potable-water report — with the specific certificate numbers available on request for your submittal pack.

Two honest limits belong here. First, a certification travels with the fitting-and-contour pair it was granted on — it does not licence you to press that fitting with a different profile. Second, exact approvals vary by market and by product line, so the right move before you commit a project is to request the current certificate set for the specific fittings and sizes you intend to install rather than relying on a general claim.

A worked scenario: switching a radiant-heating crew without re-tooling

Picture a radiant-heating installer running eight two-person crews across residential retrofits. Each crew carries a Novopress or REMS battery gun and a case of TH-profile jaws in 16, 20, 26 and 32 mm — bought years ago for a European multilayer system they no longer want to keep paying a premium for. The fear is real and specific: switch fitting brands, get the profile wrong, and a leak surfaces after the screed is poured and the floor is finished. That is a demolition callback, not a wipe-and-retry.

The path that avoids it is boring on purpose. First, confirm the incoming fitting is offered in the TH contour the crews already own — for Hitze multilayer press fittings, it is. Second, order a small sample lot and have one crew press test joints in each diameter, then take those joints to the pressure bench and hold them under sustained load, replicating the factory’s own hydrostatic check. Third, only after the sample joints pass do you roll the fitting into live jobs. No new guns, no new jaws, no change to how the crews physically work — the sequence at the pipe end is identical, because the contour is identical. The only thing that changed is the invoice and the margin on it.

The same logic scales up for a distributor. If your resale customers press TH and U multilayer systems, stocking a full range in those two contours plus M for the metal side lets you serve almost the entire installed base of press tools in your territory from one supplier — which is the difference between reselling a commodity and owning a system. For the underlying pipe those fittings press onto, our multilayer PEX-AL-PEX pipe is built to the same DIN and EN ISO regime as the fittings, so the pipe-and-fitting pair is warrantable as one system rather than a mix you have to defend joint by joint.

Best for, and not for

Open-contour press fittings in TH, U, F and M are the right call for:

• Contractors who already own mainstream press guns (Novopress, REMS, Klauke, Ridgid, Milwaukee) and want to change fitting brands without re-tooling.
• Distributors and wholesalers who need to serve a whole territory’s installed tool base from one full-range, certified supplier.
• Radiant-heating installers standardising a mixed fleet of crews on a single, warrantable pipe-and-fitting system.
• Private-label and project buyers who want their own brand on a fitting that presses with tools the market already carries.

They are not the automatic answer when:

• A project specification mandates a single named proprietary system end to end — there, you match the spec, not the contour.
• Your crews only own a closed “system” jaw (some Viega Smartpress / Uponor S-Press setups) and there is no budget for an open-contour jaw set.
• The job is a small one-off where a push-fit or compression joint is faster than owning press tooling at all — press economics reward volume.

Frequently asked questions