Pumping station selection for foul and drainage waters

The provision of a pumping system is becoming more common in many developments as gravity cannot always be deployed and a pumped solution would be critical to the success of the scheme.

Pumping stations fall into 3 main categories

  • Package Pumping Stations for small to medium applications, normally domestic up to small housing estates and commercial sites. Not Adopted by Water Companies. Short lead times.
  • Adoptable Pumping Stations for medium to large housing estates where the pumping station will be adopted by the local water company. The design for the pumping station is set out in the current Adoption specification with amendments for the local water company. This type of Pumping Station is normally a civil construction with the mechanical and electrical components added separately rather than pre-assembled as per the above package solution. Long lead times due to adoption process and design acceptance.
  • Larger bespoke pumping systems for drainage, flood control and foul schemes. Normally a major infrastructure project and site specific by design. Long lead times

Frequently, specifiers find the design and selection of a pumping station to be complex and most specifiers rely on the supplier to size the pumping station and select the pump(s) to achieve the required pumping performance.

Focusing on Package Pumping Stations have become popular due to the economy, short lead times and speed of installation, replacing the old method of labour-intensive construction of the chamber. The market has many providers who supply packaged systems based upon price, rather than quality reliable construction and endurance.

Pump chamber design has changed dramatically over the years with a preference to polyethylene being a stronger and more durable material, without the risks that GRP brings both in manufacturing quality control, life expectancy and potential environmental risk.

The selection of a pumping station and key components within requires specialist knowledge to achieve the economy and environmental performance, along with the understanding of the application that the system will serve plus the risks associated.

The manufacturers design of the package pumping station should be carefully considered, and evidence should be sort for the design integrity in the form of FEA (Finite Element Analysis) and certification by a recognised test house such as BBA (British Board of Agrément), that the chamber will be able withstand the hydrostatic pressures at the required installation depth. Many suppliers will argue that concrete will safeguard the chamber from collapse, this not true as most concretes are permeable, therefore it is important that the chamber is designed to accept such hydrostatic pressures that will be present in the ground during and post installation. Chamber failure may result in a complete system failure and considerable environmental risk subject due to the medium that is contained within. An extremely expensive issue to correct and normally requires full removal and replacement of the chamber.

Strong consideration to the environmental performance of pumping stations is key, with emphasis on energy consumption, repairability, life expectancy and recyclability. A well-designed pumping system should promote such key elements within its design, using quality materials within its construction and reliability of the same being key.

Package Pumping Stations should arrive on site ready to be installed into the ground. Once aligned, levelled and with both inlet and discharge pipework connections made, the chamber can be backfilled with concrete, a suitable cover slab set in place and with the final electrical connections to the control system also provided, final commissioning can take place.

To ensure that the pumping station has long term reliability and a long life it is essential that the pumping station is maintained in accordance with the manufacturer’s instructions.