Septic Tank Installation Cost

Septic Tank Cost Calculator

How Much Is a Septic Tank Installation?

Installing a septic tank is common in rural areas that don’t have a mains sewer connection. A septic tank handles all household wastewater — toilets as well as sinks, showers and appliances — before it drains to a compliant soakaway or drainage field.

In 2025, the average septic tank installation cost for a classic UK home centres around the £1,200 mark for the tank itself. Total install time is usually between 2 and 7 days depending on the dig and ground.

The size of the tank and the ground conditions are the two big levers on septic tank prices and how long the job takes:

• Small tank (low occupancy) — costs less but requires more frequent emptying.
• Medium tank (most homes) — balanced cost to install a septic tank and maintenance interval.
• Large tank (bigger households) — higher upfront, fewer pump-outs.

The last factor that moves the needle is the groundwork. This is where most of the variation in the cost to install a septic tank comes from:

• Drainage field (legal requirement) — every system needs a compliant soakaway or drainage field. This must be sized to your soil tests.
• Excavation — shallow, open digs are quicker. Deep digs, clay/rock, roots or tight access add time and spoil removal.
• Access and reinstatement — getting plant in/out, then making good lawns, paths or drives afterwards.

You ideally want to hire a specialist septic tank installer (not a general installer). They’ll size the system, design the drainage field, and handle Building Regulations sign-off. Typical septic tank labour costs run between £150 and £250 per day.

For the full rundown of septic tank installation cost and what affects it on your plot, see the tables below, then compare a few written quotes from local septic tank installers.

Planning and building regs do apply — see the Planning Permission and Building Regulations section of this guide for what’s typical and what to check.

Septic Tank Installation Price List

You should hire a professional septic tank installer to fit your septic tank, as they will do the job efficiently without making mistakes. It's recommended to compare a few quotes so you make sure you get the best price for installing a septic tank.

Here are the prices you can expect for septic tank installation:

Labour Cost of Septic Tank Installation

Septic tank specialists will charge £150 to £250 per day. The whole septic tank installation process can take anywhere from 2 to 7 days.

Timescales depend on weather conditions, the condition of your soil, and any other extenuating factors — so you should budget a contingency in case of these events if the installer is not working on a fixed cost basis.

Septic Tank Maintenance Costs

Once installed, you’ll have ongoing emptying and basic upkeep to budget for. Most households empty roughly once a year, but usage and tank size matter. For example, smaller tanks or bigger households may need more frequent visits.

Septic tank emptying costs can vary a bit, depending on your tank’s capacity.

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Factors That Impact Septic Tank Installation Costs

Prices shuffle around a little based on a few practical things on site. Here’s what makes the biggest difference:

Drainage or Soakaway (Required)

Every system needs a legal way to discharge — normally a soakaway or drainage field. Direct discharge from a septic tank to a watercourse isn’t allowed under the current rules. Your installer should test the ground and size the drainage field correctly.

Excavation

Digging is often the swing factor. The cheapest option is shallow, easy ground with clear access. Deep digs, clay/rock, tree roots, or working around services all add time and spoil removal.

As a rough guide, extra excavation beyond a straightforward dig can add roughly £400 to £1,200 on smaller installs. If the ground is exceptionally hard or access is fairly tight, then you’ll pay anywhere from £1,500 to over £3,000 (plus skips for spoil). Get this itemised in the quote.

Landscaping & Making Good

Once the tank and drainage are in, you’ll likely want the area put back tidy — levelling, new turf, paths or driveway patches if they were disturbed. Keep it septic-related. Agree what’s being reinstated and what’s not, so there are no surprises.

What Are The Signs of Septic Tank Failure?

Unfortunately, septic tanks can fail from time to time. Here's what to look out for:

• Bad odours coming from the septic tank or drains
• Slow flushing or overflowing toilets
• Gurgling drains
• Ground movement near either the septic tank or soakaway
• Septic tank contents spilling out onto your land

Even with a good install, issues can crop up over time. The main causes of septic tank failure are:

• Rupture of tanks
• Improper maintenance, or infrequent pumping
• Flushing inappropriate items (oil, grease, paint, sanitary products)
• Incorrect tank size for household
• Groundwater issues such as a high water table, or as a result of recent heavy rainfall

It's important to speak with your septic tank specialist to understand what you can do to mitigate these issues and prevent big problems from occurring once you've had your tank fitted.

Planning Permission and Building Regulations for Septic Tank Installations

If you’re installing or replacing a septic tank, check Building Regulations Approved Document H (Drainage and waste disposal) for the rules on non-mains foul drainage, and the Planning Portal’s guidance on non-mains drainage for when permissions and building control apply.

• Building regs apply (Part H). Your installer must meet drainage rules (tank sizing, siting, ventilation, drainage field spec) and have the work signed off.
• Planning permission: For most single-dwelling domestic installs, a below-ground tank within the property boundary is often permitted development. You may still need permission in protected areas, if you’re significantly altering ground levels, or where access works are substantial.
• Discharge rules (the big one): In England/Wales, small domestic discharges can usually run under the “General Binding Rules” — but only to a drainage field. Direct discharge to a watercourse isn’t allowed for septic tanks.
• Registration/permits: If you don’t meet those rules (e.g. high flows, tricky ground), you may need to register or apply for a permit with the regulator (Environment Agency in England, Natural Resources Wales in Wales).
• Setbacks and siting: Keep clear of buildings, boundaries, and water sources. Your installer should confirm distances and the drainage field location during the survey.
• Paperwork: If your contractor can’t self-certify, you (or they) must notify building control for sign-off. Keep copies — they’re often requested on sale.

Not sure which bits apply to you?

Ask your installer to confirm: building control route, whether you’re within the General Binding Rules, and if any local planning quirks affect your plot.

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Can You Install a Septic Tank Yourself?

DIY aside, you still need to meet building regulations and the discharge rules — see the Planning Permission and Building Regulations section for the basics. For most households, it’s safer (and quicker) to use a pro and get the work signed off properly.

An underground septic tank will need drainage works (usually a drainage field) and Building Control sign-off. Planning permission is site-dependent, not automatic. It’s worth leaving the tricky bits to a specialist and comparing a few written quotes.

You should hire a septic tank specialist to install your septic tank, as they will have the essential skills and experience to do the job to a high standard. If you’re not experienced in installing septic tanks or carrying out the digging work to fit the tank, you could run the risk of making a mistake.

Checklist: How to Find and Hire a Septic Tank Installer in the UK

Here's what you should keep in mind when searching for a septic tank installer near you:

• Gather at least 3 quotes from local drainage specialists to compare their prices for septic tank installation.
• Make sure your quotes are in written format, and have itemised lists of exactly what's included in your quote. Check to see if waste removal is included, or something you'll need to pay for separately.
• Look at the septic tank installer's website or portfolio. Do they have experience in your exact installation type?
• Take a look at their past customer reviews, taking note of any comments on good timekeeping, cleanliness on site, and evidence of health and safety regulations.
• Check that your contractor has insurance to cover you if any accidents happen on-site during installation.
• If you're having a septic tank installed for the first time, make sure your contractor will register this for you with the Environment Agency or with Natural Resources Wales, that they have the necessary building permits, and are aware of any underground utilities in the area.