A Comprehensive Guide to the Cost of Wastewater Treatment Systems

So, you’ve realised that you need a wastewater treatment system for your property and you’re wondering, how much will it cost? 

Perhaps this is for your new build property that cannot be connected to mains drainage. Perhaps you’re replacing an old system that is no longer working and needs an upgrade. Perhaps you’re being forced to upgrade your existing septic tank to a full wastewater treatment system to meet the new Environment Agency guidelines. Whatever the reason, you’re now wondering how much this is going to cost you.

Well firstly, it’s important to realise that there are many options. It’s not dissimilar to asking, “how much will my new car cost?” Of course, with what you probably know about cars, the answer to this question will vary massively dependent on what type of car you buy. Your new Vauxhall Corsa is not going to cost you as much as your new Range Rover Sport. So, the first thing to realise is that there are both Corsa and Range Rover equivalents of wastewater treatment systems, meaning that depending on whether you want a top of the range ultra-high-spec system, or you just want a system that will do the job in the most simplistic and basic way possible, you’re going to pay different amounts of money. 

From the outset, let’s be clear by pointing out that we’re not saying one is better than the other – that’s not the case. We’re simply using this analogy to point out that there are differences, and many people choose to buy Vauxhall Corsa’s and many also choose to purchase Range Rovers. Both get you from A-B so they both do the job intended, it simply comes down to the buyer as an individual to decide which to buy in relation to their individual desires and requirements. 

The most simplistic of wastewater treatment systems, if you’re allowed to use it, is a cesspool. For a domestic property of 3 to 5 bedrooms, this could cost you as little as £500 to buy. So that’s your starting point. Sure, you may find one slightly cheaper if you shop around online, but you’re going to be starting at around £500 for a most basic underground tank, which can be used as a cesspool.

A cesspool is simply a holding tank for the wastewater from your property. Imagine a large underground bucket, if you will. It simply holds the waste, out of sight, and when it’s full you have to get it emptied. 

One up from this is a septic tank. Still widely used in England & Wales, less so in Scotland, but in areas where you are allowed to use a septic tank which overflows to a drainage field or soakaway, this is your next option up the price scale. Depending on the size of property, you’ll be paying somewhere between £800 and £1500 for a septic tank. 

A septic tank will take all your wastewater from your home and the tank is usually separated into 2 chambers. The sewage builds up in the primary chamber, where the solids settle and sink to the bottom and the cleaner water naturally rises to the top. As it fills, the cleaner water that rises to the top will gradually flow into the secondary chamber and as the level continues to rise it will eventually drain out of the tank and into a perforated pipe system which disperses in a drainage field or soakaway, typically under your garden lawn. 

As you can imagine, the sewage in the primary chamber continues to build up over time, so at roughly 12-month intervals you also need to get this emptied. You don’t want the tank to be completely filled with the solids otherwise this will block your drainage pipes and the system will fail. Regular maintenance will prevent this. 

Upwards to A) a cesspool and B) a septic tank, is C) a full biological wastewater treatment system.

The main difference with a treatment plant like this is the level of treatment that takes place inside the tank, which actually cleans the water. Depending on which system you choose, the water from your wastewater treatment system will be clean enough to flow directly into a watercourse such as a river, stream or the sea. There are exacting standards to allow you to discharge into watercourses, but there are plenty of systems available which meet these high standards and make this perfectly possible. 

For a 3-to-5-bedroom home, a full sewage treatment plant will cost anywhere from £2000 up to £3000, perhaps even £4000 if you want the “Range Rover Sport” equivalent. What’s important to look into here is what’s the difference between the £2000 system and the £4000 system – there will be differences, even though they are fundamentally providing the same service, just like your Corsa also gets you from A-B. 

Even though both systems will provide the sewage treatment that you need for your property, there will be different levels of effluent quality depending on which system you choose. You can liken this to the emissions from your choice of car. Choose a certain car and the emissions will be high, choose something else and the emissions could be the lowest on the market. You can use both to get yourself from A to B, but the amount of pollution will depend on which car you chose. It’s similar with your choice of treatment plant. Choose one system and the water will be clean enough to flow into the river but choose another system and the water will be so clean it will improve the quality of the water in that same river! 

What else will be the difference between paying the least amount for your treatment plant and paying top dollar? Well, just like cars, shoes, handbags and kitchen sinks, not all wastewater treatment systems are made equal, there are many things that you may deem worthy of a higher price tag. Automations like ‘holiday mode’ which detects when there is a decrease in the amount of incoming waste which reduces the amount of movement and therefore bacteria growth, meaning the system has to react and adjust to ensure the treatment standard remains high. Things like warning lamps and alarms that can sound automatically in the event of some sort of failure or issue that needs to be addressed. Remote monitoring systems that give the homeowner the ability to remotely login to their wastewater system to change settings, to check things, to carry out maintenance checks and be proactive in looking after their system. Additional treatment packages that can add carbon dosing or phosphate, or UV systems, or chlorine, to add to the treatment process if this is a requirement. 

Depending on your specific requirements and the standards you’re looking to achieve, you’re unlikely to spend anything more than £3000 for a sewage treatment plant for a 3, 4 or 5 bedroom house in the UK. Of course, that’s just the system purchase price, you’ve got to factor in the cost of actually installing it, which is going to depend greatly on what else is being done to your property at the same time. You may spend as little as £500 to £1000 on a more basic septic tank form of treatment plant, but if you go this route it’s important to factor in the cost of the drainage field you have to install for the system to overflow to and disperse into the ground – this can be a big cost if your soil is not very suitable for infiltration. 

Like most things, there are many variables and lots of things should be factored in to make the right decision for you. Hopefully this sets you off on the right course, perhaps raising more questions than you had before! If so, we’d be pleased to talk through it with you to help you in your decision-making process. The other articles in our knowledge centre may also help, if you’d like to keep on reading.

Callum Vallance-Poole

Marketing Coordinator - Based at our UK HQ in Banbury, Oxfordshire, Callum is responsible for promoting Water Management Systems, Attenuation Tanks, Treatment Plants, Rainwater Harvesting Systems and more!