Cutting PVC properly
Square, and deburred inside and out. Those two things decide whether the joint seals, more than the cutter you used.
Square matters more than clean
A PVC fitting works by the pipe bottoming out squarely in the socket. Cut at an angle and one side of the pipe reaches the shoulder while the other leaves a gap, and solvent cement bridges a gap poorly.
Freehand sawing is where this goes wrong. A ratchet shear or wheel cutter is square by construction. A saw needs a mitre box, a pipe cutting jig, or at minimum a line marked all the way around the pipe with a strip of paper wrapped as a guide.
- Shears and wheel cutters
- Square automatically, because the tool sits around the pipe rather than being aimed at it.
- Saws need a guide
- A mitre box, a jig, or a paper strip wrapped round to mark a true line. Eye alone is not close enough.
- Check before cementing
- Dry fit and look at the shoulder. A visible gap on one side means cut it again.
Deburr and chamfer, or the joint fails
Cutting leaves a burr on both edges. The internal burr disrupts flow and catches debris. The external burr is worse: it scrapes the cement off the socket wall as the pipe goes in, leaving a dry line exactly where the joint needs to be wet.
So a solvent weld joint wants a slight chamfer on the outside edge, not just the burr knocked off. On a push fit with a rubber seal it matters even more, because a burr will cut the ring as the pipe passes it.
- Chamfer the outside
- A slight taper, not just deburring. It lets the pipe enter without wiping the cement off the socket.
- Deburr the inside
- Flow, debris and, on a push fit, the seal. A knife or a deburring tool does it in seconds.
- Never leave swarf inside
- Shavings from a saw travel to the first bend and start the blockage themselves.
Cold PVC cracks
Below about five degrees, rigid PVC becomes noticeably more brittle, and a ratchet shear that cuts cleanly in a warm van will split the pipe outside in January. The split often runs well past the cut and is not always obvious.
In cold weather use a fine toothed saw or a wheel cutter instead, and inspect the cut end before fitting. Warming the pipe in your hands or in the van for a few minutes also helps more than it sounds like it should.
- Under 5 degrees, use a saw
- Shears concentrate force in one line and that is where cold PVC splits.
- Inspect the end
- A cold split can run 50mm up the pipe and still be hard to see. Flex the end and look.
- Warm the pipe
- A few minutes indoors or in the van. Free, and it makes shears usable again.
Diameter decides the tool
Up to about 32mm, ratchet shears are quickest and cut square in one squeeze. From 32mm to 50mm, shears still work on thin wall but a wheel cutter or a saw is more reliable on thick wall pressure pipe.
Above 50mm, and certainly on 110mm soil pipe, it is a saw and a guide, or a large chain or wheel cutter. No handheld shear will span that, and forcing one is how a soil pipe ends up with a crushed oval end.
- Up to 32mm
- Ratchet shears. One squeeze, square, no swarf, and quick enough to do a run of them.
- 32 to 50mm
- Shears on thin wall, wheel cutter or saw on thick wall pressure pipe.
- 50 to 110mm
- Fine tooth saw with a guide, or a large wheel cutter. Soil pipe is always a saw job in practice.
- In situ
- A pipe already fitted needs an internal cutter or a flexible wire saw, because nothing else has room to work.
Dust and offcuts
Sawing PVC produces a fine dust that is an irritant, and power sawing produces a lot of it. On any quantity of cutting, especially in an enclosed space like a loft or a duct, a mask is sensible.
Never cut PVC with an abrasive disc. It melts rather than cuts, gives off fumes you do not want to breathe, and leaves a melted lip inside the pipe that will catch debris permanently.
- Mask for volume cutting
- PVC dust irritates the airways, and a loft or a duct concentrates it.
- Never an abrasive disc
- It melts the pipe, releases fumes, and leaves an internal lip that becomes a blockage.
- Eye protection with shears
- A cold pipe can split and release a fragment with real speed when the ratchet lets go.
- Collect the offcuts
- Small PVC offcuts in a floor void or a trench are the debris that blocks the drain you just built.
Frequently asked questions
- What is the best tool for cutting PVC pipe?
- Ratchet shears up to about 32mm, because they cut square in one squeeze with no swarf. A wheel cutter for thicker wall pipe up to about 50mm. A fine toothed saw with a mitre box or a jig for anything larger, including 110mm soil pipe.
- Can I cut PVC pipe with a hacksaw?
- Yes, and it is often the right tool above 50mm. Use a fine blade, around 24 to 32 TPI, cut in a mitre box or against a wrapped paper line so it comes out square, and deburr and chamfer the end afterwards because a saw leaves a burr on both edges.
- Why did my PVC pipe crack when I cut it?
- Almost certainly because it was cold. Below about five degrees rigid PVC becomes brittle, and ratchet shears concentrate force along one line, which is where it splits. Use a saw or a wheel cutter in cold weather, or warm the pipe first.
- Do I need to chamfer PVC pipe before gluing it?
- Yes, for solvent weld. A square cut edge scrapes the cement off the socket wall as the pipe goes in, leaving a dry line exactly where the joint needs to be wet. A slight external chamfer lets it enter without wiping the socket clean.
- What is the difference between ratchet shears and a wheel cutter?
- Shears close a blade through the pipe wall in stages and are quick, clean and square, but they concentrate force and can split cold or thick wall pipe. A wheel cutter scores progressively all the way round, which is gentler and slower and needs clearance to rotate.
- How do I cut a pipe that is already fitted?
- An internal pipe cutter driven by a drill for a stub in a socket, or a flexible wire saw passed behind the pipe and worked from both ends. Both are slow and both work in clearances where no conventional cutter can be turned or squeezed.
- Can I use an angle grinder on PVC?
- No. An abrasive disc melts PVC rather than cutting it, produces fumes you should not breathe, and leaves a melted internal lip that catches debris permanently. It also makes an end that cannot be sealed properly. Use a saw.
- How do I make sure the cut is square?
- Use a tool that surrounds the pipe, like shears or a wheel cutter, and it is square automatically. If sawing, use a mitre box or a pipe jig, or wrap a strip of paper around the pipe and mark along its edge, which gives a true line right around.
