The location of access points, relative to soil pipes, needs careful consideration during design and construction. Soil pipes and direct connections from WCs discharge to much higher velocities than gullies and whilst carrying solids, pose a much greater risk of deposits accumulating within the chamber due to splashing and thus causing blockages. Furthermore, as some of the discharge to any drain will always be forced upstream, the risk of solids accumulating in the channel must also be considered.
Although Technical Guidance Document H – Drainage and Wastewater Disposal of Building Regulations 2010 recommends that a foul wastewater system should minimise the risk of blockages, it does not provide any further guidance on addressing splashing. In the UK, the NHBC (National House Building Council), the UKs version of Homebond, offers some guidance on the matter.
The NHBC recommends that the primary channel entry connection is used for all high velocity discharges and in some cases in conjunction with swept or long radius bends. However, they refer to the design of the connections rather than the location of the access point itself.
Anyhow, such guidance has not been applied at this property in Cork City and although there are items that should not be entering the drainage system, the result is splashing and the accumulation of deposits and persistent blockages. The only course of action is to change the layout of the drainage locally with respect to the above guidance.