How Much Does a Septic Tank Cost?

Firstly, who needs a septic tank installed?

Fitting a septic tank is a particularly common job for those who live in rural areas as it can be very difficult to access any mains sewage systems. Septic tanks will remove any "grey water" from the shower, sink, and other running water in the home.

Septic tanks are useful because they help eliminate waste naturally, through use of a filtering process.

What can affect the overall costs of septic tank installation? Various factors can affect the septic tank cost, including the location, type, material, and labour.

But what about specific septic tank cost?

The typical material costs for a medium-sized septic tank is usually around £1,200-£2,000, whereas the average cost for a large tank is around £2,900-£3,500.

Green septic tanks

In general, there are two important decisions to be made in terms of a septic tank, depending on its intended use and the space available - the design, and the material it's made from.

What size septic tanks are available?

Septic tanks are typically between 4,500-12,500 litres. The different sizes can alter the job's overall cost as larger tanks will take longer to install.

The average cost to get a septic tank installed by a professional is around £2,400-£6,300. This includes the cost of materials, labour, and waste removal.

Septic Tank Prices

The table below highlights the average costs that you can expect to pay for different-sized septic tank installations:

Septic Tank Size Average Cost Duration
Single-chamber 4500 litres £2,400-£3,600 2-3 days
Single-chamber 8500 litres £3,200-£4,200 2-4 days
Single-chamber 12500 litres £4,100-£5,500 3-5days
Multi-chamber 4500 litres £3,000-£3,500 2-4 days
Multi-chamber 8500 litres £3,900-£5,700 3-5 days
Multi-chamber 12500 litres £5,700-£6,300 5-7days
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What are the Supply Costs of Fitting a Septic Tank?

The material used to construct your septic tank is a cost factor in the overall cost of installing a septic tank. The higher the quality of the material that is used, the longer you can expect the septic tank to last. However, higher-quality materials are also more expensive.

Budget septic tanks are usually made from concrete whereas high-quality tanks are usually made from fibreglass materials. Whether you choose to buy a single-chamber septic tank or a multi-chamber tank can affect the supply costs as well.

Metal septic tank in the ground

A typical single-chamber septic tank is around £1,200-£3,700 and a multi-chamber septic tank is usually around £1,800-£4,500 on average.

The table below highlights the costs you can expect for the different types of septic tank:

Septic Tank Material Average Cost Per 1000 Gallon Tank
Concrete £1,500-£2,000
Plastic £1,000-£1,500
Fibreglass £600-£1,400

What are the Additional Costs of Septic Tank Installation?

You may need to consider some additional costs when you have a septic tank installed by your home. You may also need to think about the costs of maintaining the tank. Although it only needs minimal maintenance, it's still an additional cost that needs to be considered.

The recommended maintenance of a septic tank is a yearly pressure wash to keep it in its best condition. A professional pressure wash on a septic tank will cost around £100-£200.

Septic tank installation by crane

Your septic tank may also be prone to weed growth due to the surrounding ground. If that is the case, you may need to spray weed killer on your septic tank. It's recommended that you do this twice a year. You can purchase a large tub of weed killer for around £30-£60.

A drainage system is now part of building regulations, so you may want to install a septic tank soakaway system. This will usually cost around £500-£800 and will need to be replaced roughly every ten years depending on its condition.

Tradesmen Costs for Fitting a Septic Tank

The labour price for fitting a septic tank is usually around £1,200-£1,800 for a straightforward job. If the space is hard to access or any problems arise during the installation, you can expect this cost to increase so you should be sure to budget for large labour costs.

You may be able to bring the labour costs down if you do some or all of the excavation work yourself. However, you will most likely have to hire a digger to do this part of the work yourself.

On average, a septic tank specialist will charge around £150-£250 per day. For this type of work, though, there will usually be more than one contractor working in a team, and the labour costs will be factored into the overall cost of the job.

Those based in the London area can expect to pay more for the cost of labour than those based in the North or other parts of the UK.

How Long Does It Take to Install a Septic Tank?

The time it takes to install a septic tank can vary. Some factors that can affect the time it takes to install include the size of the tank, the materials used, and the area of excavation. Ease of access can also play a part in the amount of time it takes.

The average septic tank installation job usually takes around 3-6 days to complete.

Choosing a Septic Tank

There are several different types of septic tank, and they are often made up of different materials. They are usually made up of either concrete, brick, or fibreglass.

The most common type of septic tank in the UK is the onion-shaped tank. Below is a list of the various septic tanks and the characteristics of each type:

Brick and Concrete Septic Tank

Most older septic tanks are made from brick, stone or concrete. These septic tanks usually include two chambers next to each other and a pipe that supplies air to the tanks. These can still be found in many areas; however, they are not common in the UK.

Brick septic tank


  • Contains two chambers


  • Not that common in the UK

Onion-Shape and Torpedo Tank

The onion-shaped fibreglass septic tank is the most common type of tank installed in the UK. There is also a "torpedo" tank. This is a cylindrical tank. Both of these types of tanks go into the ground similar to the more traditional brick and concrete tanks.

Onion shape septic tank


  • Most common type of UK tank


  • There can be issues with their outlet level

Over-Ground Septic Tank

Another type of septic tank is one that goes above the ground. Overground septic tanks are usually intended to be temporary. Unlike other types of septic tank, these don't need planning permission to be installed.

Over ground septic tank


  • They don't need planning permission


  • Intended as a temporary measure

How Much Does It Cost to Empty a Septic Tank?

On average, a contractor will charge around £150-£250 to professionally clean and empty a septic tank. However, the cost of the service will vary depending on a number of factors including the size of the tank, the ease of access, and the time it takes to complete the job.

Hiring a professional to come to do your septic tank emptying is the best way to maintain it and keep it in a good state.

Emptying a septic tank

The tradesman will visit your property and assess the scale of the job and insert a special hose into your tank designed to suck out all of the waste that has accumulated.

Once the tank has been safely emptied, the tradesman will then wash the chamber to remove any leftover solids that remain in the chamber.

It will also be inspected for any damage or cracks. Any repair work that is needed on the chamber should be completed after the tank has been emptied.


Q: How does a septic tank work?

A: A septic tank treats domestic wastewater and sewage by allowing bacteria to naturally break down any potentially harmful substances.

The solids will sink to the bottom of the tank, meaning the settled liquid on top contains a very low level of contamination. This can safely be drained away into a soakaway and the ground.

Q: How often does a septic tank need to be emptied?

A: As a general rule of thumb, your septic tank should only need to be emptied every 3-5 years.

Q: Why does my septic tank need to be emptied?

A: Some of the solids collected at the bottom of the septic tank will be digested by bacteria and disappear.

However, the remaining sludge will build up over time and will need to be removed. Emptying a septic tank is the best method of septic tank maintenance.

Q: Why does my septic tank have scum on top?

A: The scum layer on the top consists of fat, oil, and grease. This is a result of normal domestic activities such as cooking and washing up.

Q: What should I avoid pouring down my drains if I have a septic tank?

A: You should avoid pouring bleach down the sink or toilet if you have a septic tank. You should also limit the amount of fat that you dispose of down the drain.

Some other things that may have a negative impact on the bacteria in your septic tank include animal litter, coffee grounds, cigarette ends, sanitary items, greases and fats, paints, detergents, paper towels, wet wipes and pesticides.

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Author: Dean M

I have a Bachelor's Degree in Creative Digital Media, I'm a freelance writer and I've worked for clients such as the British Blockchain Association and I have experience in writing articles, YouTube video scripts, online guides and newsletters. I have written and produced many short films as well as a web series and feature film. I am also currently working on a novel.