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Cutting a Downpipe: Which Saw Should You Use for PVC, Zinc and Aluminium?
Cut a PVC downpipe with a fine-toothed handsaw, a hacksaw or a jigsaw with a metal-cutting blade. For zinc and aluminium, use a hacksaw or a jigsaw with a fine metal-cutting blade, not an angle grinder. Mark the cutting line all the way round, hold the pipe firmly and deburr the edge after cutting.
Cutting a downpipe is a quick job once you know what the pipe is made of. The material decides which saw you use and how carefully you need to work.
What will you learn in this article?
- Why would you cut a downpipe?
- What is your downpipe made of?
- Which saw should you use for a downpipe?
- At what height should you cut the downpipe?
- How do you cut a downpipe straight?
- How do you finish the cut edge?
- How do you reconnect the pipe?
- Which safety precautions should you take?
- Frequently asked questions about cutting a downpipe
- In short: cutting a downpipe
Why would you cut a downpipe?
The most common reasons are:
- Connecting a water butt or a rainwater diverter.
- Disconnecting a downpipe from the drain and leading the water to a soakaway or into the garden.
- Replacing a damaged section.
- Cutting a new downpipe to length during installation.
If you plan to disconnect a downpipe from the drains, check with your local council or water company first. Water must drain away safely without causing damp or flooding near your own or a neighbour's property.
What is your downpipe made of?
Before you choose a saw, you want to know what you are cutting.
| Material | How to recognise it | Saw |
|---|---|---|
| PVC | Grey, black or white plastic, light, sounds hollow | Fine-toothed handsaw, hacksaw, jigsaw |
| Zinc | Matt grey metal, dulls over time | Hacksaw, jigsaw with fine metal-cutting blade |
| Aluminium | Often coated in a colour, light metal | Hacksaw, jigsaw with metal-cutting blade |
| Asbestos cement | Grey, thick-walled, heavy, stone-like | Do not cut it yourself |
How do you recognise an asbestos downpipe?
Asbestos cement downpipes and guttering were used until the UK banned asbestos in 1999. They are heavy and thick-walled and feel like stone. If you have any doubt on a building built or refurbished before 2000, do not cut. Cutting releases asbestos fibres that damage your lungs.
Which saw should you use for a downpipe?
PVC downpipe
PVC is easy to cut. A fine-toothed handsaw or hacksaw gives a neat cut. With a mitre box you are guaranteed a square cut. For a downpipe that is already fixed to the wall, a cordless jigsaw is handy. With a fine metal or plastic-cutting blade and the pendulum action switched off, you cut quickly and neatly without an extension lead. A jigsaw or reciprocating saw from the Maxxpack 18V range does the job and runs on the same battery as your other tools.
Zinc or aluminium downpipe
Zinc and aluminium are soft metals. A hacksaw with a fine blade works well. If you prefer a power tool, use a jigsaw with a fine metal-cutting blade at a low to medium speed. A pipe cutter can work on small diameters, but most downpipes are too big for one.
Why not an angle grinder?
An angle grinder creates a lot of heat and sparks. On zinc, the edge discolours and you get a rough burr. On coated aluminium, the coating burns. On PVC, the material melts. A saw gives a better cut with less risk.
At what height should you cut the downpipe?
That depends on what you are connecting.
- For a water butt: put the butt in place first, on a stand if you use one. Measure where the inlet or overflow needs to go and allow for the section that fits into the butt or the connector.
- For a rainwater diverter or water butt filler: follow the measurements in the instructions. The diverter has to sit higher than the overflow of the butt, otherwise the butt will overflow.
- For a new bend or drain connection: measure up to where the bend slides over or into the pipe.
Measure twice before you cut. A section that is too short is awkward to put right.
How do you cut a downpipe straight?
Mark the height
Mark the height with a marker pen.
Mark the line all the way round
Wrap a strip of paper or tape tightly round the pipe and draw a line along its edge. The line is then at the same height all the way round.
Secure the pipe
If the pipe is on the wall, check that the brackets above and below the cutting line are firmly fixed.
Cut along the line
Cut steadily along the line. With a handsaw, turn the pipe or move round it so you are always cutting on the side facing you. Support the lower section so it does not break off and tear the edge.
If you are working from a ladder, set it up on firm, level ground and do not overreach to the side. It is better to cut a section lower down and fit it afterwards than to cut above your head. Our guide on how to clean gutters safely covers safe ladder work at the same height.
How do you finish the cut edge?
After cutting there are burrs on the inside and outside. They catch debris and make fitting awkward.
- Remove burrs with a deburring tool, a sharp knife or a half-round file.
- Chamfer the outer edge slightly if the pipe has to slide into a socket or bend. It slides in more easily and does not damage the seal.
- With PVC, smooth the edge with fine abrasive paper.
- Clean and dry the pipe if you are going to glue it.
How do you reconnect the pipe?
PVC downpipes are usually push-fit or solvent-welded with PVC cement. A connector or diverter slides over or into the pipe. Zinc is usually push-fit and sometimes soldered. Secure a loose connection with a bracket so it cannot slip. Check after the first heavy shower that everything is watertight.
Which safety precautions should you take?
- Wear gloves. Metal edges are sharp.
- Wear safety glasses, especially when cutting above shoulder height.
- Have someone foot the ladder when you work at height.
- Remove the battery from the saw when changing the blade.
- Never cut into a pipe you suspect contains asbestos.
Frequently asked questions about cutting a downpipe
Which saw is easiest for a downpipe?
For PVC, a fine-toothed handsaw or hacksaw with a mitre box is easiest. If the pipe is already on the wall, a jigsaw with a fine metal-cutting blade is quicker. For zinc and aluminium, choose a hacksaw or a jigsaw with a metal-cutting blade.
Can you cut a downpipe while it is fixed to the wall?
Yes, as long as the brackets above and below the cutting line are secure. Support the lower section and cut steadily. A cordless jigsaw or reciprocating saw is handy here because there is no cable in the way.
How can you tell whether a downpipe contains asbestos?
Asbestos cement pipes are grey, heavy and thick-walled, and were used until 1999. Only testing gives you certainty. If in doubt, do not cut it yourself and call in a licensed asbestos contractor.
Do you need to deburr the downpipe after cutting?
Yes. Burrs catch leaves and debris and damage seals when you push the sections together. A deburring tool, knife or file is all you need.
In short: cutting a downpipe
Check what your downpipe is made of first, and leave suspected asbestos cement to a licensed contractor. Use a fine-toothed handsaw, hacksaw or jigsaw with a metal-cutting blade, never an angle grinder. Mark the line all the way round, support the pipe while you cut and deburr the edge before you reconnect it.
