How long does it take to install a septic tank?

How long does it take to install a septic tank system?

It takes approximately one to two weeks for a below-ground septic tank system to be installed by a professional. These tanks are inserted down into the ground and include either a drainage field or secondary filter system.

Above-ground septic tanks can be installed quicker. They store wastewater only, and unlike below-ground septic tanks, above-ground installations do not include treatment and drainage systems.

An above-ground septic tank is often only a temporary sewage solution. As this type of septic tank has less features, installation can often be completed in a single day.

Factors influencing septic tank installation time

The installation time of a septic tank will depend on:

• Weather conditions – Heavy rainfall can saturate the soil and create poor construction conditions. Rain can also interfere with the drainage systems being put in place
• Ground and site conditions – Your installation site needs to be prepped before excavation work can begin. More time will also be needed if there are obstacles (e.g. fences and shrubs) that need to be removed from the installation site
• System size – Larger septic tanks take more time to install. More time is needed for excavation work, creating the drainage field and backfilling the hole
• Applying for planning permission – If you are installing a septic tank for the first time, planning permission will be needed. Contacting your local planning authority and waiting for planning approval can add several weeks to your project

We recommend asking your septic tank installer for an estimated timeframe for your project.

Installing a septic tank

A septic tank installation often includes the following stages:

• Site visit and planning
• Site preparations
• Excavation work
• Tank installation
• Drainage field installation

The length of time it takes to complete each stage will impact the overall duration of your installation.

Here’s a closer look at the septic tank installation process:

Apply for planning permission

Planning permission is needed for all new septic tank installations. Contact your local council and ask to be sent to the local planning authority (LPA).

Building regulations approval is also needed. Before proceeding with a septic tank installation, make sure you have all the legal requirements covered.

Site visit

We recommend doing your research before hiring a septic tank installation company.

Approach multiple tradespeople and spend time reading customer reviews. Once you have found the right installer for the job, they will visit the installation site.

During this stage, a professional will examine the ground condition and make plans for your installation. Measurements may be taken, and this is your opportunity to ask any questions you may have about how long it takes to install a septic tank.

Site preparations

Fences, walls, and shrubs may need to be removed before installation work can begin. Your project will take longer if several obstacles need to be removed from the installation site.

Depending on the layout of your septic system, any items removed may be able to be reinstalled once the work is complete.

Excavation

As the name suggests, below-ground septic tanks are installed into a hole in the ground.

Larger tanks typically take longer to install because more excavation work is needed. Bad weather can also delay your project, as digging in wet soil can be dangerous.

This stage can also be time consuming if you need to wait for diggers and other equipment to become available.

Install the tank

Once the hole has been made, the tank’s base will need to be built. A septic tank base is usually made from concrete and must be installed before the tank can be lowered into the hole.

Specialist equipment is used to install the septic tank securely in place. Finally, the hole is filled with either gravel, concrete or sand.

Install drainage field

A drainage field – or drainage bed – is needed for the majority of septic tanks. A below-ground septic tank must be connected to a drainage field or secondary filter system.

Any fluids that have been filtered away from the tank will flow through pipes into the drainage field.

Once in this part of the system, filtered fluids pass through perforated pipes and seep down into a layer of gravel. The contaminants in the wastewater are then broken down by microorganisms present in the ground, before finally passing down into the soil.

Installing a septic tank drainage field takes approximately a week. Bad weather and poor soil conditions can extend the duration of this phase of your project.

Connect pipes and cover the tank

The final stage of the installation involves connecting the inlet pipe to your home’s drainage pipe. The system’s outlet pipe will also need to be connected to the drainage field or a secondary filter.

Finally, make sure the septic tank is covered. Sealing the tank with a manhole cover will prevent any people or animals from falling in.

Cost of installing a septic tank system

Just like installation times, septic tank installation costs can vary significantly.

The size of your septic tank will determine your project quote. Larger tanks are more expensive and also take more time to install.

Large septic tanks have an average installation cost of £6,000. This price includes the cost of the tank, plus excavation and installation labour fees.

It costs £4,200 to install small tanks and an average of £5,000 to install a medium sized septic tank.

Replacing an old septic tank with a new system is less expensive and will cost, on average, £4,000.

Take a look at our septic tank installation cost guide for more information.

Key takeaways

• It takes an average of one to two weeks to install a septic tank
• Bad weather and poor ground conditions can impact the duration of your installation
• Above-ground septic tanks can be installed in a day
• An experienced tradesperson can provide you with an estimate timescale for your project
• Replacing an old septic tank takes less time than installing a new system
• Septic tank installation costs vary. It costs an average of £6,000 to install a large tank and £4,200 for smaller installations

Finding septic tank installers near you

We recommend hiring an experienced professional to install your septic tank system.

Find approved and verified septic tank installers near you by entering your postcode below.