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Buying a house with a sewage treatment system/septic tank

Buying a new house is likely to be the largest purchase you will ever make, and it can get very confusing when you start weighing up advantages and disadvantages between your shortlist of properties!

If you are looking to buy a house in a rural area, maybe with its own land or far away from other houses, you may well find that it comes with its own private drainage system. This could be in the form of a sewage treatment system, a septic tank or even a cesspool.

Private drainage systems are necessary for any property that is unable to connect to a main drain. Connections to a main drain depends on the location of the drain, and how far you would need to excavate within a highway to get to that drain. You will also need permission from your local water authority to connect, and your local council to excavate on their land.

Having your own private drainage system means that you are responsible for maintaining it. If you neglect to keep it serviced and emptied (de-sludged), which results in discharging untreated effluent into the ground or a watercourse, you will be liable for a fine from the Environment Agency.

If you do find a house that has its own sewage treatment system, septic tank or cesspool, don’t be put off! With the correct maintenance, these systems should work for many years without any problems.

A sewage treatment system, as the name suggests, is a system to provide full treatment of incoming sewage to a level that the treated effluent discharged is suitable to go directly into a watercourse (ditch, stream, culvert etc.) The process of treating the sewage differs slightly between different types of treatment system, but essentially the sewage enters the system, is treated by bacteria inside the tank, and the solids that cannot break down settle into a sludge at the bottom, and the resultant treated liquid waste is discharged out of the system. This sludge builds up over time and requires periodic emptying from a licensed waste removal contractor. Most sewage treatment systems require some form of power, either for a motor that rotates media discs inside the system, or an air blower that aerates the sewage – many systems also come with a control panel and alarm. This means that there are moving and working parts that need to be annually checked by a qualified engineer.

A septic tank is designed to connect to a soakaway/drainage field, which is a connected series of slotted pipework constructed underground. The sewage enters the tank (which is usually a classic ‘onion’ shape or a more cylindrical shallow-dig style), and the solids settle to the bottom. The liquid rises to the top, making contact with oxygen which starts to break down the organic matter biologically. The liquid still contains sewage, but in small enough particles to be carried through the discharge outlet and into the soakaway. The liquid travels along the soakaway and drains into the soil for further anaerobic treatment. Although a septic tank contains no moving parts and therefore does not require servicing, you will still need to organise emptying (de-sludging) from a licensed waste disposal contractor. You will also need to conduct a percolation (porosity) test to check that your soil conditions are suitable for the liquid to soak into. Failure to do this could mean that your soakaway fails and backs up into the tank, which will mean having to replace it entirely.

A cesspool is simply a storage tank for all sewage, both solid and liquid waste. There is no discharge outlet and no treatment – you simply have to organise a licensed waste disposal contractor to regularly emptying the cesspool. As there is no discharge, cesspools can fill very quickly and need careful monitoring to ensure they do not overflow.

Regardless of what system is already in place, it is important that you ensure the vendor(s) have kept records of maintenance carried out over the months/years that it has been installed. Your solicitor is likely to request this information from them – aside from having the correct documentation so you can be confident the system has received the appropriate maintenance, the Environment Agency ask that records are kept for reference if there was ever a discharge issue in the future.

You should also consider that the treatment system currently in place is highly likely to have been sized for the number of bedrooms that the property currently has. Therefore, if you plan to extend the property in the future, it’s very important that you check that the system will be able to cope with the extra sewage. For this, you will need to ascertain the make and model of the system. This should be on any documentation from when the vendor(s) purchase the system, or on any maintenance sheets from when it has been serviced or emptied.

Finally, if you get the opportunity to see the system and it appears neglected, the covers looks damaged or there is a bad smell, this could point to problems. It’s always worth getting the system assessed to ensure that it is in good repair, as replacement of a sewage treatment system can be several thousands of pounds when you factor in supply, installation and commissioning. If you’re not sure, give us a call on 01388 537050 and our engineers will be happy to advise over the phone, and we may be able to inspect the system and provide recommendations.