If your home isn’t connected to the mains sewage network, or you are thinking of buying a home which isn’t connected to the mains sewage system, you need to treat your wastewater at home. This is all the water from your sinks, shower, bath, toilets, washing machine and dishwasher.
The two main ways of treating wastewater at home are using either a septic tank or a sewage treatment plant.
But what is the difference between the two, and which is the best choice for you?
Sewage treatment plants and septic tanks serve the same purpose, in that they both provide buildings with a way to process wastewater, but there are several differences between them.
Septic tanks are the most common way to treat wastewater at home. They are underground, watertight tanks, which separate liquid waste from solid waste.
The liquid waste from a septic tank flows out of the tank into an area known as a soakaway or drainage field (which will generally be part of your garden!), where naturally occurring bacteria break down any remaining waste.
The solid waste sinks to the bottom of the tank, forming a sludge. While some is broken down by bacteria, the remaining solid waste will need to be pumped out by a registered contractor on a regular basis.
A sewage treatment plant is sometimes seen as the modern upgrade to a septic tank. It is also a tank buried underground, but it does far more to treat your wastewater than a septic tank, making it significantly cleaner and less harmful to the environment.
The waste liquid flows into the sewage treatment plant, initially in the same way as it does in a septic tank, and gravity separates solids and liquids. In a second chamber, oxygen is introduced through an air pump, which encourages the growth of bacteria, which break down the sewage into a cleaner effluent.
The clean effluent is then discharged into a third chamber, before being discharged safely into the environment. The remaining solid waste is then removed periodically by a registered contractor.
Pros and cons
Cost
The initial cost of a septic tank is significantly less than a sewage treatment plant, but a septic tank will need emptying more regularly, pushing up the running cost.
And while a sewage treatment plant will need emptying less often, it will need servicing more regularly than a septic tank (about once a year) to ensure it keeps running effectively. This will add to the overall cost of a sewage treatment plant.
A sewage treatment plant requires electricity to run, which will increase the running costs slightly. Costs will vary depending on the size of the tank and the exact technology it uses, but expect to pay something in the low three figures every year for electricity.
The law
In some instances, you will have no choice but to install a sewage treatment plant rather than a septic tank. It is important to check the latest regulations before installing a septic tank, with the Environment Agency in England, SEPA in Scotland, NRW in Wales or DAERA in Northern Island.
- A septic tank cannot discharge directly into a watercourse eg river, stream, ditch or lake.
- You cannot install a septic tank in Zone 1 of a Groundwater Source Protection Zone.
- A septic tank can only discharge into a soakaway/ drainage field which complies with Building Regulations or BS6297. This means it must be not too close to any buildings, boundaries or watercourses; away from electrical cables and pipework; not part of a road, driveway or other areas where vehicles drive; it has passed a series of tests to ensure the soil is suitable for drainage and there’s no risk of contamination of watercourses.
Size
Whether you are buying a septic tank or a sewage treatment plant, you need to be sure it has a big enough capacity to deal with the wastewater of the full potential occupancy of a home, development or business.
Generally, septic tanks are more suitable for single households or small development sites, which have enough space to develop a soakaway system. Sewage treatment plants are a better choice for bigger developments or commercial premises.
The environment
A sewage treatment plant is by far the most environmentally friendly option, as it discharges much cleaner effluent into the environment than a septic tank.
When considering whether a septic tank or sewage treatment is best, it really depends on a number of factors, including cost and any site restrictions. The most important thing is to ensure you comply with the laws around wastewater treatment. If you have any doubt at all whether a septic tank would be legal, it is important to speak to an expert.
Here at Tanks for Everything, we can give clear advice on the right choice for your own individual circumstances, to make sure you invest in wastewater treatment for your home or business which is legal, effective and suits your individual needs.
