An Expensive Waste – Sewer Pumping Station
Sewer Pumping Station
We recently completed a full building condition pre-purchase survey for a client and they were surprised to see in their report that a sewer pumping station was installed to the drive of the property under consideration. We think it important that potential house buyers fully understand why these systems are installed and what can go wrong.
Wherever possible, we will always test for foul drain leaks using pneumatic drain bungs but in this particular case we quickly realised that this wouldn’t be possible because on lifting the inspection chamber cover we noted that an underground sewer pumping station (sometimes called a lift station) was installed. These stations are used to transport wastewater to higher ground where the waste can then be further transported by gravity flow. These lift stations are generally designed to handle raw sewage where the site topography is too low to allow the transfer of effluent to the main sewer under natural gravity flow.
The basic design principle for these systems is that raw sewage is fed to an underground pit or ‘wet well’, where it is stored until the effluent reaches a predetermined level, at which point the effluent pump kicks in and pumps the effluent to the main sewer. The pump will run until the level in the wet well reaches its predetermined minimum level. These minimum and maximum levels are determined by float valves in the wet well that are linked to an alarm system in the electronic control panel. The sewage pumps are generally open end suction centrifugal pumps, often macerator pumps to break down solids into a more fluid sludge.
The system is electronically monitored by a control panel linked to the centrifugal pump and float valves in the wet well. In this particular case the FLYGT control panel was located in the garage and we did wonder whether any high levels alarms or other anomalies would be picked up in time to take action before problems such as overflowing of the wet well were seen. Our experience of these systems is that they are generally reliable so long as they are adequately maintained but common problems we have seen is fat deposition and build up within the well leading to clogging and blockages. This is raw sewage and you do not want to experience one of these sewage pits overflowing, which we have seen on another occasion due to failure of the float valve switch system.
Beyond lifting the wet well cover for visual inspection and checking any maintenance log or records there is little else that can be done during a building survey but visual inspection of the wet well is essential to check that effluent levels sit between the the float valves and to further check for fat build up and deposition. On visual inspection everything appeared fine with this particular system but we did note that the system has over ran its last inspection date by around 3 years. The current owner clearly did not take out an annual maintenance contract on this system and perhaps did not fully understand the implications of not adequately maintaining the system. In fact we enquired of a specialist maintenance company in Derbyshire as to the cost of an annual maintenance contract and were quoted £186.00 plus VAT and parts. We actually think this is a reasonable price to pay for peace of mind and all being well, with regular maintenance, we see no reason why this system shouldn’t provide many years of trouble free service.