What is the 135 rule in plumbing (and does it apply in Bolton)?

Quick Answer

The 135 rule isn't a UK regulation — it's an American rule of thumb saying you should never make more than 135° of pipe bends between drain access points without an inspection point. UK plumbers working in Bolton follow BS EN 12056 and Part H of the Building Regulations instead, which set similar limits to keep waste pipes rod-able.

What the 135 rule means

The 135 rule says that the total angle of bends in a drainage run between any two access points (rodding eyes or inspection chambers) must not exceed 135°. Beyond that, if the pipe blocks you physically can't push drain rods through to clear it.

It's a North American shorthand. In the UK we follow BS EN 12056-2 and Approved Document H of the Building Regulations, which use the same principle — keep runs reasonably straight and provide access — but specify it in slightly different ways.

Why it matters in Bolton homes

We come across breached versions of this rule constantly in older Bolton extensions, where waste pipes have been routed around obstacles with multiple 90° bends and no rodding access. The result is a drain that blocks every six months and can't be cleared without lifting floorboards.

If you're planning a new kitchen or bathroom, insist on a rodding eye at every change in direction over 45°. It costs almost nothing during first-fix and saves hundreds in callouts later.

Need a Bolton plumber today?

Phil Conroy is a Gas Safe registered plumbing & heating engineer covering Bolton and the wider Greater Manchester area. For a free written quote on any job — from tap repairs to a full boiler installation — call 07863 789484 or message us here. For round-the-clock issues, see our emergency plumbing service.