Unless otherwise specified, catchpits and not manholes must be used on adoptable highway drainage systems.
Structures (typically over-sized chambers and cover slabs which are greater than 1050mm in diameter), even if they are to be adopted by the relevant water company, must still be demonstrably designed to the relevant loading standards for retention within the highway (Eurocodes).
A catchpit must be provided (an access chamber, with sump, on a drainage system) where there is any discharge into an existing or proposed ditch or watercourse.
On all drainage runs that are to be adopted, where the pipe diameter is 900mm or less, a catchpit must be provided at:
- every change of alignment or gradient;
- the head of all main pipelines;
- every junction of pipelines except for single-gulley connections;
- every change in pipe diameters; and
Outfall to existing highway drain
If the outfall is to an existing highway drain, you will have to prove its capacity and condition before we can approve the connection. For all works incorporating highway drainage you will need to carry out and provide a copy of a CCTV survey and report. You must carry out any improvement works found necessary, all at your expense.
Catchpit and Manhole Positions
Catchpits or manholes should normally be located within the verge, and not the carriageway, on classified roads and other roads with a higher status than a residential access road or industrial access road. The outside of catchpits and manholes should be at least 500mm from the kerb line or the edge of the carriageway.
Any catchpits or manholes within a carriageway must be located so that they can be accessed while providing the necessary maintenance access safety zones (1m) and without preventing traffic from passing. This will generally mean that they should not be sited at or near the centre of the carriageway or within a width restriction. Care should be taken when locating catchpits or manholes within junctions or roundabouts, based on the above criteria.