Below Ground Pump Chamber Installation Guidelines

• Excavate the minimum opening in the ground to receive the pump chamber and pipework to be used. The depth of excavation needs to be at most, 500mm deeper than the overall tank depth. A sump should be left in one corner for dewatering purposes.

• A dewatering pump MUST be used to remove any groundwater present & provide a dry excavation until the concrete backfill is set.

• Some clean hardcore should be placed and consolidated in the base of the excavation. Usually this will need to be around 200mm thick, but in good ground, should be a minimum of 50mm.

• In order to be protected from any external force the chamber should be completely surrounded by concrete. The concrete surrounding the chamber should be of suitable thickness, usually a minimum of 150mm, and quality to protect the chamber from all external pressure. Whether this is ground pressure, groundwater pressure, trafficked areas or any other force which may cause damage or deformation to the chamber. Therefore we recommend a qualified civil/structural engineer is consulted to specify the correct concrete backfill suitable for your specific site requirements.

• Pour the appropriate amount of concrete on top of the hardcore and then lower the chamber onto the damp concrete allowing the flanged base joint, if fitted, to settle in, ensuring that the inlet and outlet pipes are correctly aligned.

• Fill the chamber with clean water to depth of approx. 500mm and recheck levels. Do not overfill as the chamber is not designed to hold water when not supported by the concrete backfill.

• Carefully commence pouring of the concrete backfill in small stages evenly around the chamber ensuring there are no voids which may allow groundwater to penetrate. Vibrating pokers should be used with care to avoid damage to the chamber.

• Continue filling the chamber with clean water whist evenly backfilling, ensuring the water level is no more than 300mm above the level of the concrete backfill.

• Connect up the site pipework to the inlet and outlet of the pump station, and draw the pump and float cables through the conduit to the control panel before they are encased in concrete.

• Under no circumstances should concrete be poured directly onto the chamber.
Attempting to pour too much concrete at once will result in the chamber “floating” or particularly above the half way point damage to the chamber due to excessive weight on the chamber body for which the manufacturers will not be responsible.

• Finish off the surface of the concrete at the required level, depending on the final ground cover required i.e. topsoil, tarmac, gravel etc. (see sketch below). If the access cover or the surrounding area is likely to be subject to other than purely pedestrian traffic, provision must be made to ensure that no weight loading is taken by the chamber i.e. by the construction of a cover slab, and the appropriately specified access cover must be used.