PLASSON compression fittings seal on a captive O-ring, so a leak-free join comes down to a clean pipe end, full insertion and a straight run in and out of the fitting. Cut the pipe square, chamfer and lubricate the end, push it fully through the O-ring to the centre of the fitting, then tighten the nut to hold it against blow-out. Fittings from 16 mm to 32 mm, and all rural fittings, go on hand-tight.
Step by step
Step
1. Cut square
2. Prepare the end
3. Mark the depth
4. Insert fully
5. Tighten the nut
What it means on the job
Cut the pipe with a pipe cutter‚ not a blade or saw. A jagged or angled end won't seal and can nick the O-ring.
Chamfer and lubricate the pipe end so it slides past the O-ring without dragging or damaging it.
Make a witness mark on the pipe at the insertion depth – the pipe should reach the centre of the fitting‚ so both ends meet in a coupler.
Push the pipe through the O-ring until it reaches the witness mark. You'll feel resistance before it's fully home – don't stop short‚ or it won't seal.
Do the nut up to hold the pipe against blow-out. It doesn't make the seal – Plasson's captive O-ring technology seals instantly on pipe insertion. 16–32 mm and rural fittings are hand-tight; larger metric needs a wrench.
Getting a leak-free join
A join leaks for one of a few reasons, and all of them are avoidable:
Problem
Pipe not fully inserted
Poor pipe end
Damaged O-ring
Strain on the fitting
Cause
Resistance through the O-ring makes it feel home before it is; a partly-inserted pipe won't seal.
A jagged or angled cut won't seal and can nick the O-ring.
A sharp or dry pipe end drags on the ring during insertion.
Pipe entering or exiting on an angle stretches the O-ring so it no longer seals.
Fix
Use a witness mark and push to the centre of the fitting.
Cut square with a pipe cutter.
Chamfer and lubricate the end first.
Keep the pipe straight in and out; use an elbow or swivel elbow to turn a corner instead of forcing the fitting.
PLASSON elbows handle direction changes so the fittings aren’t stressed – 90°, short-radius 45°, and swivel elbows that rotate one end to face any direction. Use them to deal with corners and bends rather than angling a straight fitting.
Guides by fitting type
The method above is the same across the range. Each guide below shows it on a specific fitting:
- Metric compression fittings: Standard metric poly. Hand-tight to 32 mm.
- Compression joiners 75–125 mm: Larger metric; bring the nut up with a wrench.
- Rural fittings (no tools): Imperial ag pipe; red barbed inserts and hand-tightened nuts, no tools.
- Poly-to-copper fittings: Converts a poly run to copper
- Slip repair couplings: Repairs a damaged section in an existing line.
- Metric MineSafe 63–125 mm: Mining-spec couplings.
- Joining different diameters: Reducing fittings and reducing sets for unequal pipe.
Click here to learn how PLASSON’s captive O-ring compression seal works.
Visit our installation guides page for more video explainers and easy-to-follow installation sheets.
FAQ
How do you install a poly pipe compression fitting?
Cut the pipe square, chamfer and lubricate the end, push it fully through the O-ring to the centre of the fitting, then tighten the nut to hold it in place.
Do you tighten the nut to seal a compression fitting?
No. The O-ring seals as the pipe goes on. The nut only holds the pipe against blow-out under pressure.
Why is my poly pipe joint leaking?
Usually the pipe isn’t fully inserted, the cut is jagged or angled, the O-ring was nicked on insertion, or the pipe is on an angle straining the fitting.
Do you need tools to install PLASSON fittings?
No, for rural fittings and for metric fittings up to 32 mm – they’re hand-tight. Larger metric fittings need a wrench on the nut.
How far should the pipe go into the fitting?
To the centre of the fitting. Use a witness mark so you can see it’s fully inserted.
How should you cut poly pipe?
Square, with a pipe cutter. A blade or saw can leave a jagged or angled end that won’t seal.
