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PVC Pipe

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Pipe Materials
Choosing and joining pipes
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PVC Pipe
Rigid plastic pipe

PVC pipe suits the distribution runs from the storage tank to the standpipes because it is cheap and rigid and its solvent-welded joints are strong, but it is brittle in cold weather and degrades in sunlight above ground, so bury it and handle it gently when it is cold. Use only pipe rated for water pressure, make every joint by cleaning, coating both surfaces with solvent cement, pushing together and holding, and let the cement cure fully before any pressure goes on.

Part of Community Water System

PVC pipe is rigid polyvinyl chloride tube, sold in straight lengths and joined by solvent cement, used for the distribution network of a community water supply.

Rigidity Gives Strong Joints And Poor Tolerance Of Knocks And Cold

The community water system page lists PVC as cheap and rigid with strong solvent-welded joints, brittle in cold and degraded by sunlight above ground, and recommends it for distribution between the tank and the standpipes. Rigid pipe holds a straight line and does not kink. It also cannot bend around obstacles the way HDPE does (HDPE Pipe), so every change of direction needs a fitting.

Not all PVC pipe is meant for pressure. Drainage and waste pipe has thin walls and no pressure class. A salvaged length of unknown type should be pressure tested before burial or used only for gravity drains, not for a pressurised water line.

What You Need

  • PVC pipe and fittings rated for water pressure (Pipe Materials)
  • Solvent cement for the pipe type, with its primer if the maker specifies one
  • A saw with fine teeth, a file or scraper and a clean rag
  • A trench, bedded with fine soil, free of sharp stones
  • Good ventilation, because the cement is flammable and its vapour harmful

Method: Cut, Fit, Cement, Cure

Step 1: Cut square and remove burrs inside and out.

Step 2: Dry-fit. Push the pipe into the fitting without cement. It should enter part way and stop firmly; mark the depth with a pencil.

Step 3: Clean both surfaces of dirt and grease. Wet or dirty surfaces make a weak joint.

Step 4: Coat both surfaces with cement, a thin even coat on the pipe end and the fitting socket.

Step 5: Push together fully and give a quarter turn, and hold for the time on the cement tin. The cement softens the surfaces and fuses them; the bead of cement around the rim should be even.

Step 6: Cure. Follow the maker’s cure time before the line is pressurised, and longer in cold weather. Pressurising early blows the joint.

Step 7: Bed and bury. Bury it so it is never in sunlight (Burial Depth). Where the pipe comes up to a standpipe, shade or wrap the exposed section.

Worked Example: Joints And Movement

Suppose a distribution branch of 300 m is laid from 6 m lengths (check the length you actually have).

  • Lengths = 300 ÷ 6 = 50, so 49 joints. Each is a cement joint to be made correctly and tested.

PVC expands less than HDPE: a handbook value is about 0.07 mm per meter per degree C, which I am recalling and which varies by compound. For a 10 m exposed section near the tank over a 20 °C swing: 10 × 20 × 0.07 = 14 mm. That is small, but it is enough to stress a rigid joint that is anchored at both ends, so a long exposed run still wants an expansion joint or a bend.

Common Mistakes

  • Using drainage pipe on a pressure line. It is not rated for it.
  • Cementing wet, dirty or loose-fitting parts. The joint weeps or fails.
  • Pressurising before the cement has cured. The joint blows apart.
  • Leaving it in the sun. The pipe goes brittle and cracks.
  • Hammering cold pipe. It shatters.

Safety

Solvent cement is flammable and its vapour is harmful; burning PVC gives off toxic gas

Work in the open air or with a through-draught, with no flame, spark or smoking nearby, and keep the tin closed. Never burn offcuts of PVC: the smoke contains hydrogen chloride and other toxic gases. Do not test a PVC line with compressed air; rigid plastic can shatter and throw sharp fragments. Wear eye protection when cutting and testing.

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