Blog>Expert Advice>Everything you need to know about installing a septic tank
Last updated: 5 September 2024
Everything you need to know about installing a septic tank
Are you thinking about installing a septic tank? Let’s take a closer look at everything you need to know; from applying for planning permission to choosing a quality installer.
What is a septic tank and what are the benefits?
Septic tanks are a type of onsite wastewater management system. While the majority of properties are connected to a main sewage network, septic tanks are often used in more rural areas.
Septic tanks are installed underground and store and treat a property's wastewater.
Fluids from a building's toilets. Sinks, showers and baths can be drained into a septic tank. This drainage system also deals with wastewater produced by washing machines and dishwashers.
Waste from your home is separated and treated inside the septic tank. Solid waste will turn into sludge at the bottom of the tank. Fats, oils and greases rise to the top and wastewater stays in the middle.
The wastewater - often referred to as effluent - is drained from the tank through the outlet pipe and moves through the rest of the septic system. The effluent is naturally treated in a drainage field which is connected by pipes to the septic tank.
Finally, the treated water seeps down into the soil.
Septic tanks are often unnecessary if your home is hooked up to the local sewage network.
That being said, a septic system has many benefits and may be your only drainage option. For instance, properties in rural areas may too far away from the local sewage line. In this situation, it is often more cost-effective and practical to install a septic tank sewage system.
Benefits of installing a septic tank
The advantages of installing a septic tank include:
Cheaper water bills - You can save money on water bills by dealing with your home's sewage yourself. However, unless you have a well or other independent water source, you will still need to pay for a water supply
Environmentally friendly - Your septic system should not leak raw sewage into the environment. These systems also filter pollutants out of the wastewater before draining it into the soil
Self-sufficient waste management - With a septic tank installed, there is no need to worry about leaks or other sewage issues. This installation allows you to be in total control of your home's wastewater disposal
Septic tank regulations
There are rules and regulations that need to be followed when replacing an old septic tank or installing a brand new system.
Specific septic tank regulations have been put in place by the government to protect the environment and public health. Your septic tank installation must comply with current regulations, as set out in the Environment Agency's General Binding Rules.
The General Binding Rules were last updated in 2023. Your septic tank must meet the following criteria to be compliant with the latest regulations:
Sewage must only be from a domestic property's toilets, bathrooms, kitchens and showers
Sewage must be checked once a month to make sure no pollution is caused
The drainage field must be at least 10 metres from a watercourse (river, stream etc) and 15 metres from any buildings
The drainage field must be installed at least 50 metres from a water supply - a well, for example
There must be no driveways, access roads or paved areas close to the drainage field
Waste must not be discharged into a watercourse. Instead, a drainage field or sewage treatment plant must be used
Waste discharges made into the ground must be two cubic metres or less per day in volume
Only a competent person can perform system maintenance
Waste sludge from the system must be safely disposed of by an authorised person
Waste must not be discharged within 30 metres of a public foul sewer
There are also General Binding Rules in place specific for septic tanks installed near conservation areas. The rules also differ slightly between systems discharging waste into the ground and those releasing waste into surface water.
We recommend reading the full list of septic tank system regulations on the government website.
Septic tank installation requirements
In addition to complying with the above criteria, it's important to position a septic tank in the right location.
A septic tank must be installed at least seven metres away from any dwelling. The tank must also be installed within 30 metres of an access point.
We recommend working with experienced tradespeople to make sure your septic tank system is installed correctly.
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Planning permission
Contact your local council and speak to your local planning authority (LPA) to find out if your project requires planning permission. Planning permission will likely be needed if you install a new septic tank system.
Different councils have different planning permission rules. We always recommend checking with your local council before making any significant changes to your property.
Unless you are changing the entire system, you can replace an old septic tank without permission from your LPA.
Septic tank permit
You may also need to be issued with a septic tank permit from the Environment Agency. It is only necessary to apply for this permit if any of the following apply:
Your property can not 'reasonably' be connected to the mains sewer line
Your septic tank system does not comply with current General Binding Rules
Your septic tank system can't be modified or upgraded to comply with current General Binding Rules
Your property isn't already connected to the mains sewer network
The Environment Agency will not issue a septic tank permit if they believe your property can be connected to the mains sewer network.
Your application may also be declined if the Environment Agency think you can update your septic system to comply with the General Binding Rules.
The following factors will be considered when you apply for a septic tank permit:
The distance between your property and the nearest public sewer
The cost of installing a septic tank system compared to the cost of connecting to the mains sewer network
Obstacles preventing a connection to the public sewer - large road, for example
The potential environmental benefits of your new sewage system
Building regulations
As well as planning permission and a septic tank permit (when needed), your new septic tank system must meet the current building regulation requirements for drainage and waste disposal.
It is best to work with a competent tradesperson to make sure your installation is compliant with all current rules and regulations.
See the tradespeople we've checked and recommend for your job
The process of building a septic system
There are several stages involved in installing a septic tank system.
It is possible to install a septic tank yourself but we recommend hiring a professional. Working with an experienced tradesperson is the best way to make sure your septic tank is compliant, secure and correctly installed.
The septic tank installation process typically includes the following stages:
Applying for planning permission and a septic tank permit
Hiring a qualified septic tank installer or team of installers
The installers will visit the site, test the soil and draw up plans
The site will be prepared. This includes removing fences and other obstacles on the installation site
Digging the hole for the septic tank
Creating the tank base, lowering the tank into position and filling the hole with gravel, concrete or sand
Building the drainage field. This step involves excavation work and laying perforated pipes in the ground
Connecting the inlet and outlet pipes
Covering the septic tank opening to prevent any people or animals from falling inside
Your installers can answer any questions you have about the installation process. They can also offer advice on the best size septic tank for your household needs.
How much does it cost to install a septic tank?
It costs an average of £5,000to install a medium size tank and this increases to£6,000 for larger systems.
As well as installation costs, you will also need to pay a professional to empty your septic tank on a regular basis. This service has an average cost of £175 for a small tank. Emptying fees can increase up to £312.50 for extra large tanks.
Read our septic tank cost guide for a closer look at current installation prices.
Installing a septic tank checklist
Make sure your septic tank system complies with current General Binding Rules
Apply for planning permission if you are installing a new septic system
Apply for a septic tank permit if your system does not comply with current regulations
Make sure your system meets all required building regulations
Hire professional septic tank installers to plan your project, and to install your tank and drainage field
We recommend contacting a local installation company for more information about installing a septic tank. The experts can tell you everything you need to know about planning your unique project.
Make sure you are working with a reputable septic tank installation company to achieve the best results. Enter your postcode below to find high quality and verified tradespeople in your local area.
All Checkatrade tradespeople have been thoroughly checked and meet our high quality standards.
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FAQs
When is best to install a septic tank when building a house?
If you are building your own home, you may be wondering when is the best time to install a septic tank.
Septic tank systems can be installed at any point during your house build. However, often installers will wait until your home has been built before installing the septic tank and drainage field.
Septic tanks are typically installed last to avoid damage to the site. For instance, heavy construction vehicles can damage the drainage field. There is also the risk of installing the system in the wrong location if you do this work first.
Installing the septic tank last also makes sense because all the property's plumbing will be done. This means you can instantly hook up your septic tank once it is installed, instead of having to wait for the plumber to finish their work.
We recommend speaking to the tradesperson managing your house build project to find out when your septic tank should be installed.
What happens if a septic tank is not registered?
If you have a non-compliant septic tank you can be fined up to £150,000 by the Environment Agency.
Continuing to use a non-compliant septic system can pollute the environment and put your health at risk. As well as having to pay a fine, you may also need to pay to 'clean up' any land that has been polluted by your septic tank.
What are the rules on selling a house with a septic tank?
If you are selling a house with a septic tank you have a legal obligation to provide your buyers with the following information:
A description of the septic drainage system. including details of any changes that have been made
Maintenance cost details and the maintenance manuals (if you have them)
The location of the septic tank
The location of the discharge point
Maintenance records
It is always best to be honest when selling a house. Your buyers must be informed if the septic system needs to be updated to comply with current regulations.
If the system needs upgrading, buyers may offer below your asking price to cover the modification costs. Alternatively, you may decide to replace the tank before putting your house on the market.
It is also likely that your buyers will ask for a drainage survey before agreeing to the purchase. The results of the survey may influence their decision to buy a home with a septic tank or not.
How long does a septic tank survey take?
A professional septic tank survey typically takes between 45 minutes and 3 hours to complete.
The duration of the survey will be influenced by the size and complexity of the septic drainage system. During the inspection the surveyor will look for leaks, clogs and damage.
The surveyor will also perform checks to make sure the septic tank is suitable for your household's sewage requirements.
How long does it take to get a septic tank permit?
A septic tank permit will be needed if your system does not comply with current General Binding Rules.
Once your permit application has been received, it takes approximately four months for the Environment Agency to make a decision.
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