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Cross-market term

Drainage access chambers

The points at which a buried drain can be reached — to inspect it, to rod it, or to enter it. Markets divide the same range of sizes differently, and the words do not line up at the small end.
  • 4Markets
  • NoSame thing everywhere
  • 3Calculators

What it is called, by market

One concept, four markets. Where a name means something else locally, the card says so rather than leaving you to find out on site.

  • United Kingdom

    Same word, different thing

    manhole

    also inspection chamber, access chamber, rodding eye, IC

    Graded by depth and access: a rodding eye takes a rod only, an inspection chamber takes an arm, and a manhole is deep enough that a person enters — which makes it a confined space with all that follows.

  • Australia

    Close, not identical

    inspection opening

    also IO, inspection shaft, maintenance hole, manhole

    Maintenance hole is increasingly the official term in Australian and New Zealand documents, with manhole surviving in speech.

  • United Statesyours

    Same word, different thing

    manhole

    also maintenance hole, cleanout, access structure

    A CLEANOUT is a capped opening in the pipe itself, not a chamber. It is the nearest thing to a rodding eye and is NOT the equivalent of a British inspection chamber, which is a boxed structure with a benched invert.

  • Canada

    Same word, different thing

    maintenance hole

    also manhole, cleanout, catch basin

    As the United States, and a catch basin is a further trap — it is a surface water inlet with a sump, not an access chamber on a foul drain.

The governing standard, by market

  • United Kingdom

    Approved Document H / BS EN 476

    Drainage and waste disposal, including where access must be provided and the sizes of chamber for each depth.

  • United States

    IPC Chapter 7 / ASTM C478

    Sanitary drainage cleanout requirements and spacing, and precast reinforced concrete manhole sections.

Calculators for this

Each works in either measurement system, and the terminology on the page follows whichever market you have selected.

Manhole Ring/Riser Segment Calculator →Drain Pipe Slope Calculator →Storm Drain Pipe Slope Calculator →

Frequently asked questions

Is a cleanout the same as an inspection chamber?
No, and pricing one against the other is a substantial error in both directions. A CLEANOUT is a fitting in the pipe run with a removable cap, brought to the surface in a small box or a cover — it lets a rod or a jetting hose into the pipe and nothing else. A British INSPECTION CHAMBER is a structure: a chamber of a specified internal size, with the drain running through it in an open channel, benching sloped up each side so that flow is guided and solids are not left standing, and a cover rated for the traffic above it. One is a fitting costing tens of pounds, the other is an excavation with a base, a chamber, benching and a cover. An American drawing that calls for cleanouts translated as inspection chambers multiplies the drainage cost several times over.
When does a chamber become a manhole, and why does it matter?
When it is deep enough that a person has to go in, and it matters because that changes it from a builder's item into a confined space. British guidance grades access by depth: shallow chambers are worked from the surface with an arm and a rod, and at greater depth the chamber has to be large enough to enter, with step irons or a ladder, and with the cover size to admit somebody wearing equipment. Entering it is then a controlled operation with gas testing, ventilation, a rescue plan and a permit — because a foul drainage chamber can hold hydrogen sulphide and can be oxygen-deficient, and both have killed people who went in to clear a blockage. That is the practical reason to design a system with as few deep chambers as the falls allow.
What is benching, and what happens without it?
Benching is the sloped concrete either side of the open channel in the base of a chamber, rising from the channel to the chamber walls. Its job is to keep the flow moving and to shed anything that surcharges back into the channel rather than leaving it stranded on a flat shelf. A chamber built with a flat base instead is a settling tank: solids drop out where the velocity falls, build up, and eventually block the outgoing pipe — so the access provided to clear blockages becomes the place that causes them. The same logic explains the channel itself being a half pipe rather than a box: the flow keeps its depth and its speed through the chamber instead of spreading out and slowing down.