Technical Guidance

Question:

Where pre-formed plastic inspection chamber bases are used does the main channel entry connection have to be used in all instances or can connections be made just via the branch connections?

Considerations:

• The entry connections should ensure no deposits can accumulate within the base where they can then lodge and cause blockages.

• The manufacturer’s installation recommendations should be followed.

• The velocity of discharges entering the chamber should not cause spillage on to the top of the benching and build up of debris which can lead to blockages.
  

Answer:

To avoid the build up of solids in the main channel the main channel entry connection should be used in all cases. Where two drains meet a base from different directions the inspection chamber should be turned and swept bends used to connect one drain to the main channel with the other drain connected via a side entry as shown below.

Regard should also be taken as to the amount and velocity of discharges entering the base to avoid splashing and build up of debris on the top of the benching opposite branch connections. High velocity discharges e.g. discharge from SVP’s should use the main channel wherever practicable.