The Cost of Installing a Septic Tank

Last updated 30th January, 2024

Do you need to know the cost of installing a septic tank?

This article includes all you need to know about the factors that affect septic tank installation costs, different types of septic tanks and septic systems. Including costs of materials, labour and time frames. On average, septic tanks cost anywhere between £1,500-£2,000.

Keep reading for more information!

Septic Tank Cost

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How Much is a Septic Tank?

Installing a septic tank is a common job if you’re living in a rural area as it’s difficult to access any mains sewage systems.

A septic tank will remove any "grey" water from running water including sinks, showers, toilets, and dishwashers.

There are five main factors you need to consider in terms of cost which can affect the price for the installation or the replacement of a septic tank system.

These are size, underground/overground location, drainage systems, material, and labour.

The average material cost for a medium septic tank would typically cost around £800, whereas a large tank would be around £1,200.

The typical size of septic tanks ranges from 4500 litres to 12500 litres, different sizes can alter the cost to put in septic tank as the bigger the tank, the longer the job will take.

The average cost to install a septic tank including materials, labour and waste removal is between £1,500-£2,000.

This price will typically fluctuate due to ground excavation work, chosen materials, and waste removal.

Septic Tank Prices

Below is the average cost of septic tank installation based on size and type.

Single-chamber 4500 litres £1,000-£1,500 2-3 days
Single-chamber 8500 litres £1,700-£,2,200 2-4 days
Single-chamber 12500 litres £2,000-£2,300 3-5 days
Multi-chamber 4500 litres £1,600-£2,000 2-4 days
Multi-chamber 8500 litres £2,000-£2,500 3-5 days
Multi-chamber 12500 litres £3,000-£3,500 5-7 days

Supply Costs

The material used to construct the septic tank is also a cost factor, as you would expect, the better quality and longer lasting materials are more expensive.

But it really is a case of getting what you pay for, so if you can afford the extra initial outlay, it’s worth paying a premium as the tank will last much longer.

Cheaper tanks are made of concrete, whereas the premium models are made of a high-density polyethylene material which will last much longer so is more economical over the long term.

Below is an average supply cost of either a single or multi-chamber septic tank when buying from an online retailer.

Single chamber £600-£800
Multi-chamber £1,000-£1,600

Below is an average pricing of the individual costs of popular materials for septic tanks.

Concrete £600-£1,000
Plastic £700-£1,200
Fibreglass £1,000-£1,300

Concrete Septic Tank Cost

Concrete is the most common choice for septic tanks because it’s extremely durable and cheap in cost.

If a concrete septic tank is well maintained and looked after, it can last up to 30 years.

Concrete septic tanks may cost between £600-1,200.

Plastic Septic Tank Cost

Plastic is another budget-friendly option due to its light material.

Plastic septic tanks are not vulnerable to cracks; however, they may collapse due to soil pressure in harsh conditions.

Plastic septic tanks may cost between £700-1,500.

Fibreglass Septic Tank Cost

Fibreglass is a pricier option but comes with a range of benefits.

They’re easy to install due to their lightness and high quality.

Although the price is higher, it may be worth investing as fibreglass won’t deteriorate or crack underground, making it last up to 50 years.

Fibreglass septic tanks may cost between £1,000-£2,000.

Additional Costs

Additional septic tank costs can be incurred through a variety of different jobs, some are work that needs to be done for the running of a smooth septic tank system.

There’s also lots of extra bits and bobs that can be undertaken at the same time.

Only minimal maintenance in the form of a once yearly pressure wash is normally required for between £100-£200.

However, any oil stains or spills should be cleaned professionally asap to prevent permanent stains.

Weed growth on block paving does not come from below the block but from surface seeding caused by airborne seeds becoming lodged into any small gaps in the paving.

This can be minimized by spraying with a weed killer twice a year and keeping the surface well sealed, you can buy large tubs of this for between £30-£60.

A drainage system is now a part of the 2020 building regulations, meaning you can install a soakaway system for around £700.

Soakaway systems will need to be replaced every 10 years depending on its condition.

A septic tank installation is the ideal time to unblock and jet drains in your household.

This can cost anywhere up to £200.

If you’re having issues with your plumbing work, this may be the chance to have your bath and sink taps replaced, which can cost between £400-£500.

Cost Breakdown Calculator

Individual costs of installing an underground, medium-sized septic tank - Total Cost: £2000






Waste removal

Labour Costs and Time Frames

A major cost factor is the labour required for the septic tank installation.

Typical installation labour costs are between £1,200 and £1,800 for a straightforward job.

This can be reduced if you can do part or all of the excavation yourself by hiring a digger, as it’s relatively simple to dig a hole.

The average septic tank specialist will usually charge around £150 to £250 per day, although labourers will often work in teams and labour costs will be factored into the overall price.

A septic tank installation can typically take anywhere 4-7 days to complete, depending on the septic tank’s size, material, and area of excavation.

For above ground septic tanks, it shouldn't take more than a day for installation so expect around £200 in labour costs on top of the cost to install septic tank.

Cost Affecting Factors of Installing a Septic Tank

The first and most obvious cost factor to consider is the size of the septic tank.

This will have a direct effect on the cost, but it is a false economy to install a septic tank which is too small, as this will just need emptying more often and will end up costing as much, if not more, than a larger septic tank.

You need to remember that septic tanks are not just used for sewage, they also take "grey water" from the washing machines, sinks, showers and dishwashers too.

In fact, all the wastewater from your home will be draining into a septic tank so you need to ensure the tank has adequate capacity.

If anything, you should be on the side of slightly too large, as the extra installation costs would usually be cheaper than more frequent emptying over the long term.

A medium septic tank would typically cost around £700-£800, whereas a large tank would be around £1,200.

Whether the tank is above or below ground also has a large impact on the price.


Underground septic tanks have additional costs in terms of excavation so above-ground tanks are generally cheaper and the best solution for minimising the septic tank price.

Having an underground tank fitted is not cheap due to the installation costs, but on small sites you may have no other option if surface space is at a premium.

In addition, the larger sizes of septic tank tend to be designed for underground usage.

When choosing you should always contact the local authority before making a decision, as they may have restrictions in place on the type of septic tank system you can use.

If you’re looking for a cheaper option, you should consider installing your septic tank above the ground as the labour costs for ground excavation will be a lot lower.

If you choose a septic tank treatment which aids the growth of active bacteria, this will break down any solids or hard waste into sludge which will lessen any foul odours and stretch out the time needed before emptying your tank.

You can buy a year’s worth of bioaugmentation products from between £20-£40.

What Does Installing a Septic Tank Entail?

Septic tank installation should be carried out by a professional tradesman as it can be a dangerous job and requires specific expertise and qualifications.

Below is a general guide on the installation process of a septic tank done by a specialist.

Survey and Prep

The first step is to have a survey carried out on the site to ensure the area is ready for installation.

There also needs to be a soil test in and around the area where the septic tank will be.

Once the survey is completed, your septic tank is ready to be designed, after all building regulations and planning permissions have been complied with.

Excavation and Wastewater Systems

The work will begin with the ground being excavated and broken down to the right measurements, the hole will have to be at least 2 ft deep so that the septic tank can sit comfortably.

If the septic tank system is gravity fed, the wastewater will flow downhill from the tank so that it can be drained properly.


If the septic tank is using a wastewater dispersion method, then steel pipes will be installed through the trench wall, levelling into the ground.


Then, a substantial concrete tank will be installed below the ground within the excavated hole.

The survey will have planned the layout of the septic drain field which will be installed after this, specialists will ensure there is a positive flow between the tank and the leach field during installation.


Once the septic tank is fit, all piping and uncovered bits will be covered up and finished aesthetically.

Once the health inspector gives the green light, your system will be good to go, and any extra works can be carried out.


If you’re having a pump chamber system installed, you’ll also need to have a chamber fitted right next to the septic tank.

This should be placed in after the septic tank has been installed and given the go ahead.

A pump chamber system will transfer sewage to flow into the leach field where it will then be disposed of.

DIY Installing Septic Tank

Some people may think it’s a good idea to install their own septic tank to try and cut down on labour costs if they’re working on a budget.

However, this can be a very bad idea and end up hiking up your DIY septic tank cost.

A DIY septic tank installation should only be attempted by a professional or someone with previous experience and professional assistance.

Before any work takes place, you will need to get planning permission from your local council.

If you’re confident enough to undertake this DIY job, then you’ll also have to have the ability to, or hire someone to dig up the ground prior to septic tank installation.


Hiring a digger can cost between £100-£200 per day depending on size.

Digging the ground, yourself will take a lot of effort, expertise and time.

You’ll also need to take into consideration that an underground septic tank will need drainage work to be carried out, this also needs planning permission.

This can be very complicated, and it’s best advised to hire tradesmen or septic tank specialists to carry out this work as they have the specific skills qualifications and experience to complete the job to the best standard.

If you do this job DIY, you risk the chance of something going wrong and damaging your home, or yourself.

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Choosing a Septic Tank

There are two main types of septic tanks which you can have installed into your housing system, these are either single chambered or multi-chambered.

Typical material choices include plastic, concrete or fibreglass as a septic tank system needs to be shielded from corrosion and water resistant.

Choosing the size of your tank will be determined by how many bedrooms your house holds, the more people in your household, the bigger the tank you’ll need.

Single Chamber Septic Tank Costs

Single-chamber tanks are ideal for a small household as its main purpose is to hold heavy solids that have settled or floated from wastewater.


If you live in a one-bedroom house, it’ll be a cheaper alternative to install a single-chamber as the needs for a multi-chamber aren't as high.

Multi-Chamber Septic Tank Costs

Multi-chamber tanks are great for bigger households who have a higher amount of effluent.

The multi-chamber will have a waste filter on the outlet which will stop solids from passing through, meaning there’s a slower process before effluent reaches the leach field and the system becomes clogged.


However, you’ll have to take into consideration that a multi-chamber will need to be cleaned and maintained far more regularly than a single-chamber tank and will add to the septic tank cost.

Septic Tank Regulations

There are specific building regulations in place that you need to follow before a septic tank installation, you’ll also need planning permission.

From 2020, new legislation has been put in place for sewage systems from the Environmental Agency.

The regulations include discharging waste from your septic tanks system via either a soakaway or waterway system.

Drainage systems are required for below-ground tanks which can also add to initial costs.

But the benefit of a larger underground tank can often be worth the initial expense at first.

This is because the soakaway can allow solids from the wastewater to be filtered out slowly into the surrounding ground, making sure that the tank does not need to be emptied as often, which will save you money in the long run.


However, not all sites will be suitable for a soak away, the ground needs to be checked to ensure it will be able to absorb some of the excess water.

Getting this checked over and having any required pipe and drainage works installed will enhance the project’s price.

Full Planning Application fees, planning, can cost up to £1500 including design fees.

The price of application and liaison building notices will cost approximately £500.

Ensure that all planning permission and building regulations have been adhered to before getting quotes from professionals for the job.

If you fail to comply with building regulations and permissions, you may suffer a fine of up to £100,000.

Septic Tank Maintenance Costs

Urban dwellers usually take sewer systems for granted, but if you live in a rural area you will likely already know all about septic tanks.

If there is no mains sewage, then homes need a septic tank to provide a place for wastewater to drain into. Septic tanks need emptying at least once a year.

Although most of the sludge in the bottom of the septic tank is broken down by bacteria, it is likely that some sludge at the bottom of the tank will remain and this will build up over time so needs to be removed.

When you hire a contractor to empty the tank, they will take the sludge but put the watery effluent back in as this contains the good microbes necessary for your septic tank to work properly.

It’s really not emptying your septic tank, but simply removing the sludge.


General maintenance should also be applied within the household when cleaning the pipes.

Make sure to not flush through bleach into your sinks or toilets as it will kill any active bacteria within your septic tank and will lessen the effectiveness of your septic tank system.

Below is a table outlining the cost of general maintenance jobs.

Emptying a small septic tank £100-£150 Under an hour
Emptying a large septic tank £200-£250 1-2 hours
Replacement soakaway system £500-£700 1 day

Removing Septic Tank Costs

Your septic tank may need to be removed and replaced if there’s blocked pipe in your household, a blocked filter system, flooding, or if there’s an unpleasant odour coming from your garden.

This happens when a septic tank is damaged, and you may need to fork out for a replacement.

If you hire a company to come and empty your septic tank, they will find the cause of the problem and either help you out with a quick fix or give you the unfortunate news that you need a new septic tank or drainage system.


Costs can differ depending on the reason why your septic tank needs replacing.

If you’re lucky, your replacement could be covered by your building insurance, meaning you will only have to pay for the excess which is usually up to £100.

However, if you need a whole new tank to be installed, this can cost anywhere between £1,000-£3,000.


A septic tank is a multi-chamber system which retains sewage from a property for sufficient time to allow the solids to be naturally broken down. The remaining effluent can then drain from the tank through an outlet pipe.

They are usually installed where there is no mains drainage and are buried in the ground.
They are basically just a way of slowing up the sewage to allow sufficient time for the natural break-up of the contamination by enzymes. The septic tank is basically a storage point for sewage and after the solids have settled the liquid effluent on top of the sludge has a relatively low level of contamination which can safely be drained into a soak-away and then into the ground.

The sludge itself is then broken down over time by naturally occurring microbes.
A septic tank is low maintenance but should preferably be emptied once every 3-5 years. This will depend on how many people live in your household and how often your water system is used.
Too many chemicals in your pipework can affect the chemical balance of your septic tank so it’s important you don’t use any cleaning products which damage your system.
Water-based cleaning products are a good choice for cleaning your household, as well as most multi-purpose household cleaners.

You may be able to get away with small amounts of household bleach, but any high strength or extra strong bleach should be avoided.
The size of your house will determine how big your septic tank will need to be.
The larger your house, the larger the septic tank.

A house under 1,500 sq. ft will work best with a 750- or 1,000-gallon tank, whereas a large house will function better with a septic tank over 1,250 gallons.
The main difference is that septic tanks have no power demand and no moving parts, so they are cheaper to install and run, but the final effluent from a septic tank will always require further treatment in a soak-away.

Whereas waste-water treatment plants usually have an electricity supply which drives a small pump to aerate the wastewater and break it down so that no soak-away is required.
The addition of bacteria into the septic tank augments the existing biological population and ensures that the tank has all the right strains of bacteria to work efficiently.
In a perfect environment this is not necessary as the biomass will be self-sustaining, but some strains of bacteria find it harder to thrive in a septic tank than others, so regular bio-augmentation guarantees your tank has sufficient bacteria of the right kind in it.
A well installed and maintained septic tank system should be able to last up to 40 years. This all depends on how well you look after it, what products you use, and the environment surrounding the excavated ground.

It’s important to make sure your installation is high quality, even if that adds cost to put in septic tank.

How to Find & Hire a Septic Tank Installer

When hiring a contractor to install your septic tank, you want to ensure that you have a specialist who is skilled, trustworthy, and qualified to complete the job. It can seem like an overwhelming task to find the right person to hire, but we’re here to help.

Below is a list of questions you want to be asking potential installers when talking with different tradesmen and comparing quotes.


Make sure you ask for proof on whether they have the correct qualifications including:

  1. General Liability and Workers Compensation insurance
  2. Installer license through Texas Commission on Environmental Quality (TCEQ)

Ask For Pictures and References

Check that they’ve undertaken this job before and have prior experience with installing septic tank systems.

Seeing previous pictures and hearing from their other customers will give you an insight into how your installation will turn out and how reliable they are.

Checking out their work will also give you peace of mind and make sure they’re not all talk.

However, if they refuse to let you see any pictures or hear references, then it may be best to look somewhere else.

Compare Quotes

Comparing quotes is the best way to make sure you’re getting the best deal possible.

It’s also a great way to fish out anyone who may be upping their prices to a layman.

Comparing several quotes will let you see the general price range of your specific job.

Set Up Payment Plan

Once you’ve found your tradesmen and have agreed on a quote, dates, surveying, and all the rest, you should set up a prior payment plan through either direct debit or cash.

Make sure to ask for a receipt to avoid any potential future disputes or problems.


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