16 May 2025

Through this series South Cumbria Rivers Trust (SCRT), on behalf of the Love Windermere Sewage Theme workstream, aim to provide essential information for owners and operators of private sewage treatment systems, including what they can do to help minimise their impact on the environment.

The sizing, management and maintenance of your private sewage treatment system is essential for it to work effectively. This links directly to how wastewater is treated by septic tanks, package treatment plants and cesspits, discussed in our last issue. Having too small a septic tank or package treatment plant comparative to the number of people using a property, can cause significant issues. For example, it can lead to sewage being flushed through too quickly, before the system has time to treat it properly. Too large a system, although generally less of a problem, can mean bacteria in the system do not receive enough food to grow, thus reducing the extent of biological treatment. For cesspits, having too small a system can mean that it needs to be emptied more frequently and raises the risk of raw sewage overflowing into the environment.

The appropriate management of drainage into your private sewage system is essential for it to work properly. Tipping excess fat, oil and grease (e.g. from cooking) and flushing non-biodegradable products (e.g. wet wipes) down the drain can cause a host of issues including blocked pipes and leaking sewage. The use of harsh cleaning chemicals (e.g. bleach) can kill the bacteria living within your sewage system, stopping them from helping remove organic matter and nutrients. That’s why it is important to put any food waste into the bin rather than down the drain, clean with septic-safe cleaning products (Fig. 1) and make sure that you are only flushing the three P’s (pee, poo, paper) down the loo, to minimise any potential issues with your sewage system.

Finally, the maintenance of your private sewage system is essential. This can be achieved by emptying accumulated solids and servicing moving parts. How often your system needs emptying will depend on its capacity and how much it is being used. Always refer to the manufacturer’s guidelines for system specific information.

If information is not available, septic tanks and package treatment plants will generally need emptying at least every two years, while cesspits require emptying at least once a year. If in doubt, contact a local licenced waste contractor.

Treatment plants with any electrical or moving parts will also require an annual service by a qualified engineer to ensure they are working correctly and safe. Any emptying of sewage waste should be carried out by a licensed waste contractor (available on EA public register), who should provide you with a waste transfer note to ensure that your waste is being treated safely and according to current regulations. Emptying of your tank by anyone other a registered waste carrier, is illegal.

Taking the time to regularly check and maintain your system can help both safeguard the natural environment and save you money. Be on the lookout for any issues like slowly clearing drains, dark or smelly pipework, and spongy or lush patches near your tank. As always, more information can also be found on the Call of Nature website at https://callofnature.info/.