Septic tanks & soakaways, sewage treatment plants, cesspits – what are they and which one is right for your home?

Sewage Treatment Plant Installation

Let’s talk dirty…

A home in a rural retreat can be truly idyllic. But living in a more remote area means there are certain aspects to consider which you might otherwise take for granted – your waste disposal being one of them. Whilst a conversation about it might not be suitable for a dinner party, it is necessary at some point.

Sewerage systems service the majority of residential Britain but if you find yourself living away from one, there are several other options available to you. The property in question may already have a waste disposal system in place but is it suitable for your needs, is it working as it should and does it meet the necessary environmental regulations to keep your land safe?

This article will look at the most common residential waste disposal systems (namely septic tanks and soakaways, sewage treatment plants and cesspits) and will guide you on what you need, why you need it and how you can ensure your waste is disposed of efficiently.

Septic tanks and soakaways – what are they?

A septic tank is typically two underground chambers made from brick, concrete or now even fibre glass or polyethylene. All the drainage waste from your home (yes, all – from every sink, loo, shower and bath) is passed into the tank where solids will separate from liquids and natural bacteria will break these solids down. The liquids pass through the system and in the past, have been allowed to drain directly into a watercourse such as a lake, pond or stream. But from 1st January 2020, this will no longer be allowed when the septic tank regulations change to better protect the environment.

However, most modern septic tanks have what is called a soakaway, which means they will already meet these new regulations. The separated liquids which pass through the septic tank reach the soakaway after the second chamber. This waste is then also partially treated by naturally occurring bacteria, making it safer to filter into the surrounding soil (which does need to meet certain criteria itself).

Septic tanks with soakaways require maintenance and some problems can occur. Firstly, emptying and de-clogging will be required by a licensed professional. Whilst the first chamber does breakdown solid waste, a residue remains that builds up over time and will need removing. Furthermore, the bacteria in the soakaway filter will create biomass as they treat the liquid waste and in addition to other silt deposits, blockages will occur that need regular clearance.

Secondly, other problems can arise if the bacteria itself is damaged by overuse of strong cleaning products, when food waste or oils/fats are poured down the sink, or if the wrong things are flushed down the drains (baby wipes, feminine hygiene products etc). It is imperative to ensure no damaging products make their way into a septic tank system or the bacteria will be very badly affected.

For successful waste management with a septic tank, the key considerations are;

  • The soil on your land needs to be of soakaway calibre
  • The system must comply with the new regulations by having an efficient soakaway
  • Regular maintenance must be undertaken
  • You must not dispose of the wrong items into the tank

How does a sewage treatment plant differ to a septic tank?

Whilst there are some similarities in that all household waste passes into a sewage treatment plant, solids are separated from liquids and naturally occurring bacteria treats the waste, there are several key differences between a sewage treatment plant and a septic tank.

A sewage treatment plant is more likely to have three underground chambers and in short, it has additional components. Basically, a sewage treatment plant pumps air into the additional chamber (often called the biozone) which enables the bacteria to do a much better job of breaking down the waste thus eliminating the need for a soakaway. Whilst you wouldn’t want to drink the resultant liquid after the third chamber, it is perfectly safe to pass directly into the watercourses we said shouldn’t take septic tank waste earlier.

The pump does require a power source, which will need servicing of course. But within the system there is an alarm meaning you will be notified when any maintenance is required. So, whilst there are more elements than a septic tank, sewage treatment plants treat waste much more effectively making them much better for the environment.

The simple cesspit

Perhaps the most straightforward of all the residential waste treatment systems is the cesspit. Like a septic tank or a sewage treatment plant, a cesspit lives underground but rather than multiple chambers, it has just one.

There is no treatment of the waste at all when it is passed into a cesspit and plainly speaking, it’s a storage space until it becomes full and requires emptying. The frequency of this of course depends on the size of the cesspit and the volume your household creates and can range from monthly to annually. Emptying can only be conducted by a licensed company and costs can be high.

Furthermore, environmental regulations stipulate that a cesspit must be a minimum of 42,000 litres (or 11m x 2m in size!) and over 7m away from the house – many properties simply don’t have enough land to accommodate this. The gases which need venting off don’t smell particularly pleasant either so you certainly wouldn’t want it any closer to your home!

As such, rather like the sewage treatment plant, there is more administration and cost involved than with a septic tank and effective soakaway. Due to the high level of potential contaminants that would be leaked in the event of a problem, the high running costs, the smell and the size of property required, a domestic cesspit should only really be considered in the event of a septic tank or sewage treatment plant not being feasible, for example if the property’s soil isn’t soakaway standard for a septic tank or there is no watercourse close by for a sewage treatment plant to empty into.

What’s the verdict?

A cesspit should only ever be considered in special circumstances – it really isn’t a particularly household-friendly option.

Septic tanks with soakaways provide adequate waste disposal if the conditions are right but there are maintenance and environmental considerations.

Sewage treatment plants treat the waste so effectively it poses no threat to the local environment, there is only minor maintenance required and you’ll be alerted of any issues so owners can live with peace of mind. It is certainly one of the most viable system for a domestic property without access to a mains sewer.

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