The Garden Guide

Drainage equipment - review

Pond Construction Guide

All but the smallest garden pools require:

  • an overflow drain to dispose of surplus water which accumulates during periods
  • of heavy rainfall. The overflow drain can be either a covered standpipe ,projecting from the floor of the pool, or an overflow outlet set into the side of the pool and discharging to a storm sewer, swale or garden stream
  • a floor drain is required for any pool of a size larger than the owner is prepared to drain with a scoop. The outlet to the floor drain should be at the lowest point in the floor and there should be a fall (eg 1:50) from each point in the pool towards the discharge point

An alternative to separate overflows and floor drains is to install a standpipe overflowwhich can be detached to allow complete drainage of the pool.

If the pool is small and there is no outlet (a storm sewer or lower land) for a gravity water, it is still worth installing a sump to which water drains from the floor of the pool. Bottom drains are often connected to filtration systems. but are also useful for occasional cleaning in biological ponds. In the long term, ponds (and lakes) are temporary phenomena. They fill up with debris.

Bottom drains work best when protected with with a domed cover. This collects debris for removal but prevents it from blocking the pipework. Domes are also available for vacuum pumps if the pool does not have a bottom drain.

From top to bottom: (1) suction strainer on pool floor (2) overflow drain setting water level, removable to drain pool(3)bottom drain on pool floor (4) sump set into pool floor