PVC Conduit Fittings: A Sparky's Guide to Bends, Boxes, Adaptors and Saddles

PVC conduit is one of those materials that electricians either do properly or bodge. When it's right, it looks clean, protects cables for decades, and makes future modifications straightforward. When it's not — poorly chosen fittings, wrong size, inspection elbows where you can't get a finger in — it creates problems every time someone needs to pull new cable. This guide covers everything you need to pick the right fittings first time.

20mm or 25mm: Choosing the Right Conduit Size

The two sizes you'll encounter on most domestic and light commercial jobs are 20mm and 25mm. Almost all domestic work uses 20mm — it's the standard for lighting and socket circuits running through walls, ceilings, and surface-mounted installations.

Move up to 25mm when you have a higher cable fill, multiple circuits sharing a run, or larger SWA cables entering distribution boards. On commercial and industrial work you might go larger still, but for a typical domestic install 20mm covers the vast majority of applications.

The key rule: never overfill conduit. BS 7671 (the IET Wiring Regulations) sets cable fill limits based on conduit size and cable diameter. If you're pushing more than four 2.5mm² T&E cables down a single 20mm conduit run, it's time to either upsize or run separate conduits.

PVC Conduit Fitting Types

Normal Bends

Used for straightforward direction changes — typically 90° — where you don't need to access the inside of the bend after installation. A normal bend is the quickest way to turn a corner. The downside: once cables are in, that bend is sealed. Use normal bends on short runs where you're confident you'll never need to draw new cable through.

Inspection Bends and Elbows

The inspection version has a removable cover that lets you access the bend for cable pulling. Always use an inspection bend on runs where you might need to replace or add cables in future — anything over about 3 metres from the last access point, or where there are multiple bends on the same run. The cover adds a few millimetres to the profile but it's worth it every time.

Couplers

Straight connectors for joining conduit lengths end to end. Straightforward — just make sure the conduit is fully seated and the coupler is correctly aligned before the installation gets boxed in. Profix 20mm Conduit Couplers come in packs of 10, which is the sensible way to buy them — you always need more than you think.

Female Adaptors

Used where conduit terminates into a knockout — enclosures, back boxes, consumer unit knockouts, and distribution boards. The male thread on the adaptor mates with a brass or plastic lock ring inside the enclosure to make a secure, weatherproof entry. Profix 20mm Female Adaptors in white come in a pack of 10 — keep a box on the van.

Through Boxes, Angle Boxes and H Boxes

Conduit boxes are the decision points in a run:

• Through box (2-way straight) — inline access point on a straight run. Use where the run is long enough that you need an intermediate pulling point. The Profix 20mm Through Box has a blanked cover you remove for pulling.
• Angle box (2-way 90°) — corner access point. Functionally the accessible version of a normal bend, but in a box form that gives more room to manoeuvre cable.
• H box (4-way) — junction point where cables split into two directions. Useful in ceiling voids where you're distributing to multiple circuits from a single incoming run.

Saddles and Spacer Bar Saddles

Fixing conduit to a surface. Standard saddles sit flat to the wall — quick, low-profile, fine for surface-mounted runs in dry areas. Spacer bar saddles lift the conduit slightly off the surface, which improves airflow around the conduit, makes painting easier, and looks cleaner in finished spaces. Profix 20mm Spacer Bar Saddles in black come in packs of 10 — standard spacing is every 500mm on horizontal runs, 800mm on vertical.

Surface vs Concealed: When to Use Each Fitting Type

Surface-mounted conduit is the pragmatic choice on commercial and industrial sites — exposed brick, blockwork, or concrete where chasing isn't practical. Use inspection fittings throughout so any future electrician can pull new cable without dismantling.

Concealed conduit (in plaster, screed, or within stud walls) uses the same fittings, but your choice becomes irreversible once the wall's closed. Plan cable routes to minimise bends. Use inspection fittings wherever there's a direction change. Draw cables before plastering — never assume you can pull them through later.

Steel vs PVC: A Quick Note

PVC is the default for most UK domestic and light commercial work — it's lightweight, doesn't corrode, and easy to cut with a hacksaw. Steel conduit is used in industrial environments, where mechanical protection requirements are higher, or where earthing continuity through the conduit itself is required. For everything else: PVC.

What We Stock at APM

We carry the full Profix conduit range in 20mm and 25mm, white and black. Browse the Conduit collection or the full Conduit Pipe and Fittings range for everything from couplers to inspection tees.

Same-day collection from our trade counter in Acton — 24 Western Avenue, W3 7TZ. Call 020 8702 8080 if you need a specific quantity or size confirmed before driving over.

Installation Tips

• Cut square — a poorly cut end won't seat properly in couplers or adaptors. Use a conduit cutter or mitre box, not a knife.
• Ream cut ends — remove burrs with a file or conduit reamer before pulling cable. Burrs damage cable insulation.
• Plan your access points before you start — inspection bends and boxes cost almost the same as standard fittings. Use them liberally on anything that'll be boxed in or plastered over.
• Pull cables with a draw wire — leave a draw wire in every conduit run, even if it's currently occupied. Future electricians will thank you.
• Don't cement in inspection fittings — they need to remain accessible. Secure them with saddles only.