One of the most common questions at the PSA counter from plumbers switching brands: “Will my press tool do these?” The tool body usually isn't the issue. The jaws are. A copper press fitting is designed around a specific jaw profile, and pressing it with the wrong one can leave a joint that looks done but isn't sealed properly.
What a press profile is
Each press fitting has a raised bead near each socket end, with the O-ring sitting inside it. When you press, the jaw closes around that bead and deforms it, locking the copper together mechanically and compressing the O-ring onto the tube. The shape machined into the jaw — the profile — has to match the shape of the bead so the force goes where the fitting was designed to take it.
- V-profile jaws have a V-shaped contour that presses the bead into a defined shape on either side of the seal.
- M-profile jaws have a rounded, double-curve contour designed for fittings with an M-profile bead.
- Other proprietary profiles exist too. Each fitting system specifies the profile it needs.
What goes wrong with a mismatched jaw
A jaw that doesn't match the bead can still close fully and leave a pressed-looking mark. The problem is what's happening inside: the O-ring may not be compressed evenly, or the bead may be deformed in the wrong place. That joint can hold on a quick test and fail later under pressure or temperature cycling. Fitting manufacturers' warranties also generally depend on using the specified profile — a mismatched jaw can void them.
Standard Press is V-profile
The whole Standard Press range — the water fittings and the red-seal solar range — uses the V-profile. Per the product data, the fittings work with Kempress, Viega and B-Press tooling fitted with V-profile jaws. Specs for the water range: up to 1600 kPa, up to 120°C, AS 3688, WaterMarked, 25-year warranty.
How to check compatibility before you buy fittings
- Read the jaw. Jaws are stamped with their size and profile. Check yours rather than relying on memory.
- Check the fitting's specified profile on the product page or packaging.
- Check the tool-to-jaw fit. Jaws are also built for a particular tool force class and mounting. A jaw with the right profile still has to fit your tool.
- Check size coverage. A jaw set that runs DN15–DN32 won't press 40mm or 50mm — larger sizes typically need different jaws, collars or a higher-force tool.
Buying a tool with the right jaws
If you're buying new, buy the jaw profile that matches the fittings you'll stock. The Novopress ACO153 kit at PSA comes with DN15–DN32 copper press jaws — if you're running Standard Press, confirm with our team that the jaw profile in the kit is V before ordering. Browse copper press tools.
Good pressing practice, whatever the profile
- Cut the tube square and deburr inside and out — a burr can cut the O-ring on insertion.
- Check the O-ring is present, seated and undamaged.
- Mark the insertion depth on the tube and insert to the mark.
- Hold the jaw square to the fitting over the bead.
- A joint pressed short or crooked isn't fixed by pressing it again — cut it out and redo it.
Costing up the switch to press? See Copper Press vs Silver Brazing.
Frequently Asked Questions
Can I press V-profile fittings with M-profile jaws?
No. The jaw profile must match the fitting's bead profile. A mismatched jaw can produce a joint that looks pressed but isn't sealed as designed, and can void the fitting warranty.
What press profile do Standard Press fittings use?
V-profile. They're listed as compatible with Kempress, Viega and B-Press tooling fitted with V-profile jaws.
How do I know what profile my jaws are?
Jaws are stamped with their size and profile. Check the stamping on each jaw rather than assuming the whole set matches.
Do I need different jaws for gas and water press fittings?
Not because of the service — the profile and size are what matter. If your gas and water fittings share the same profile and size, the same jaw presses both. Check each fitting system's specified profile.