Can I bend PVC conduit with a torch or a heat gun?

Not with an open flame. A flame scorches the outside while the inside is still stiff, chars and blisters the plastic, weakens the wall, and gives off fumes you do not want to breathe. A heat gun is slow and uneven on anything but small sizes and small touch-ups. Use a heater made for PVC conduit.

Why does my PVC bend straighten out?

It was let go before it cooled. Warm PVC keeps trying to go back toward straight, so a bend released soft relaxes by a few degrees. Hold it to the form until it is firm all the way through, cool it with a wet rag if you need to, and check the angle after it is cold.

Do PVC offsets use the same multipliers as EMT?

Yes. The multiplier and the shrink are pure geometry and do not care what the pipe is made of. At 30°, a 6" (152 mm) rise puts the marks 12" (305 mm) apart and shrinks the run by about 1 5/8" (41 mm). The difference is that in PVC each mark is the middle of the heated bend.

Why does my PVC go flat or kink when I bend it?

Either it was not heated all the way round, so the cold side resisted and the soft side folded, or it was a larger size bent without plugs. Rotate it the whole time it heats, plug the ends on bigger pipe, and form it in one smooth motion against a form rather than by hand in the air.

Cintrer du conduit en PVC

PVC conduit is bent with heat, not a bender: mark the bend, heat that section evenly in a hot box or a heat blanket while you keep it turning, form it against a jig or template, and hold it there until it cools and sets. Bigger sizes get plugs in the ends so the bore stays round. The layout — multipliers, shrink, marks — is the same geometry as steel; the one change is that each mark is the middle of a heated bend. How hot and for how long come from the heater's and the pipe maker's instructions.

Heating it

Hot box (a PVC heater). A long box the pipe lies in, heating it all round. What I use past the small sizes.
Heat blanket. A pad that wraps the section to bend. Good for a bend or two on the job, or mid-stick.
Heat gun. Small sizes and small corrections only; it is slow and easy to scorch one side.
Never an open flame on the pipe. A torch cooks the outside while the inside is still stiff, so the bend blisters, chars or kinks; it weakens the wall; and burned PVC gives off fumes you should not be breathing.

Whatever the heat, turn the pipe the whole time: soft on one side and stiff on the other flattens or folds. On the larger sizes, plug both ends before heating with the kit's plugs: the trapped air helps hold the bore round.

Heat, form, cool

Lay out. Mark the bends with a paint marker, all the way round, and a line along the top of the pipe through every mark. Each mark is the middle of a bend.
Plug the ends. On larger sizes, plug both ends before heating so the trapped air helps the bore stay round, using the plugs your heater or kit is made for.
Heat evenly. Put the marked section in the hot box or under the blanket and keep it turning so every side gets the same heat, for as long as the heater and the pipe maker say. It is ready when the heated length is evenly soft and flexible, not when one side is.
Form. Take it out and form it against a jig, a bending form or a template in one smooth motion, with the line along the top still facing up.
Hold while it cools. Hold it to the form until it is firm. A wet rag or cool water on the bend speeds it up. Do not let go while it is warm or the bend relaxes.
Check. Check the angle with a level or an angle finder, and lay offsets on the floor to see they sit flat, before you heat the next bend.

There is no degree scale on a hot pipe, so bend to something: the kit's bending form, a plywood jig cut to a radius, a line chalked on the floor, or the first good bend as a template. The radius of your form must be at or above the minimum your code book sets for the pipe size.

Laying out an offset or a 90 in PVC

Heat a zone centred on each mark, long enough for the whole curve. Marks are rise × the multiplier apart, as on steel.

An offset is laid out exactly like one in EMT: marks rise × the multiplier apart, the shrink added to the overall length. Use the offset calculator for the figures. A heated bend is a gentle curve, so centre it on the mark; that puts its corner where the arithmetic expects it.

The heated length has to cover the whole curve, plus a little each side so the curve does not end in a hard shoulder. The curve's length is the radius × the angle in radians: 0.393 × the radius for 22.5°, 0.524 × for 30°, 1.571 × for a 90. Heat a zone that long, centred on the mark.

A 90 stub-up has no stamped take-up, because there is no shoe. The take-up is whatever your form gives: bend one test 90 on it, measure from the start of the curve to the back of the finished bend, and use that figure in the stub-up calculator for every 90 on that form and pipe size. A big sweep is easiest as one long heat on a large form; if the curve is longer than your heater, work it as short heated sections, spaced by the segmented bend calculator.

Worked examples

Stepping out 6" (152 mm) past a footing, at 30°

The run has to jog 6" (152 mm) out, and the offset should start 24" (610 mm) from the coupling. Mark 1 — the middle of the first bend — at 24" (610 mm). Mark 2 at 6 × 2 = 12" (305 mm) further: 36" (914 mm). Shrink 6 × 0.268 = 1 5/8" (41 mm), added to the length. The jog covers 6 × 1.732 = 10 3/8" (264 mm) of run. Bend 1, cool, check, then bend 2 with the line still up.

A 7 7/8" (200 mm) offset at 22.5°

Rise 7 7/8" (200 mm). Marks 200 × 2.613 = 20 9/16" (523 mm) apart, bend middle to bend middle. Shrink 200 × 0.199 = 1 9/16" (40 mm) on the length. The jog covers 200 × 2.414 = 19" (483 mm) of run. 22.5° means a shorter heated zone.

What goes wrong

The bend relaxes

What you see: the angle is a few degrees short once it is cold; an offset has less rise than laid out.

Why: let go while still warm. PVC springs back while it cools, not after.

Fix: hold it to the form until firm, cool it with a wet rag, check it cold. A small error can be reheated and reformed.

Flattened or kinked

What you see: an oval bore or a crease on the inside of the bend.

Why: uneven heat, no plugs on a larger size, or bent in the air without a form.

Fix: cut it out.

Scorched or whitened

What you see: discoloured, blistered or white, chalky patches.

Why: too much heat in one place, or left in too long.

Fix: cut it out; the wall is damaged.

A dog leg

What you see: the offset rocks on the floor.

Why: the second bend was formed out of plane with the first.

Fix: a line along the top before you start, facing up for every bend. Unlike steel, a small one can be reheated and set true.

Factory elbows vs field bends

For a plain 90 or 45, a factory elbow is quicker, rounder and exactly its angle; glue it and move on. Field bends earn their time on offsets, odd angles, kicks, stubs at an exact height, and anywhere a factory radius will not fit. Either way, every degree counts toward the limit in your code book between pull points. The conduit types page has what else changes from steel to PVC.

Safety

Burns. Hot pipe and heater surfaces burn through thin gloves; wear heat-resistant ones.
Fumes. Overheated or burned PVC gives off harmful fumes. Work with ventilation and never heat past soft.
Follow the instructions. Heating time, temperature, plugs and cooling come from the heater's and the pipe maker's instructions for your size. No chart here replaces them.

Questions

How do you bend PVC conduit?: With heat, not a bender. Mark the bend, heat the marked section evenly in a hot box or a heat blanket while turning it, form it against a jig or template, and hold it there until it cools and sets. Large sizes get end plugs so the bore stays round. How hot and how long come from the heater and the pipe maker, not a rule of thumb.
Can I bend PVC conduit with a torch or a heat gun?: Not with an open flame. A flame scorches the outside while the inside is still stiff, chars and blisters the plastic, weakens the wall, and gives off fumes you do not want to breathe. A heat gun is slow and uneven on anything but small sizes and small touch-ups. Use a heater made for PVC conduit.
Why does my PVC bend straighten out?: It was let go before it cooled. Warm PVC keeps trying to go back toward straight, so a bend released soft relaxes by a few degrees. Hold it to the form until it is firm all the way through, cool it with a wet rag if you need to, and check the angle after it is cold.
Do PVC offsets use the same multipliers as EMT?: Yes. The multiplier and the shrink are pure geometry and do not care what the pipe is made of. At 30°, a 6" (152 mm) rise puts the marks 12" (305 mm) apart and shrinks the run by about 1 5/8" (41 mm). The difference is that in PVC each mark is the middle of the heated bend.
Why does my PVC go flat or kink when I bend it?: Either it was not heated all the way round, so the cold side resisted and the soft side folded, or it was a larger size bent without plugs. Rotate it the whole time it heats, plug the ends on bigger pipe, and form it in one smooth motion against a form rather than by hand in the air.