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Empty Septic Tank Costs: 2023 Price Guide (UK)

Photo: Sustainable Sanitation Alliance Secretariat / Flickr / CC BY 2.0

Many rural areas of the UK don’t have mains drainage due to remoteness or local geography. So, it’s normal for properties in these regions to use a private septic tank rather than pay a water company to remove and treat wastewater. This purpose-built container receives the discharged foul and wastewater from a property. It settles and contains the solids while allowing the decanted water to percolate into the surrounding soil, subject to strict regulations. However, you must pay for solids removal when the tank’s full.

The average cost of emptying a septic tank ranges from £100-£400, depending on your tank’s capacity and other factors we’ll discuss later.

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This guide explains how septic tanks operate, the regulations governing their use, how much it costs to empty and clean them, and the factors affecting the price.

How Much Does It Cost To Empty A Septic Tank?

Manufacturers produce several standard-sized septic tanks. Modern tanks are moulded from glass reinforced plastic (GRP) or polyethene (PE) and arrive on site ready to drop into a previously excavated hole and connect to the drain pipes. In contrast, septic tanks in older properties, built before the strict regulations, were constructed in situ from concrete or brick and were made to any convenient size. 

Septic Tank CapacityNumber of ChambersRecommended Emptying FrequencyAverage Cost to Empty
4,500 LSingle Chamber12-24 months£100-£150
8,500 L£150-£200
12,500 LMulti-Chamber£200-£250
17,500 L£250-£350

The table above shows the standard sizes, recommended emptying frequency and the average cost to empty using a local waste disposal contractor. Note that these estimated average prices will vary depending on several factors.

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Factors Affecting Emptying Septic Tank Prices

Several factors affect the estimates you receive from a waste disposal contractor for emptying a septic tank.


The waste disposal contractor will need access for a vehicle and suction pipe. Many contractors charge for the amount of time they are in attendance. So, it’s in your interest to ensure a parking place as close to the tank as possible. Contractors will charge for a failed visit, so ensure you have done everything possible.

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Remove any obstructions between the vehicle and the tank, such as fences. If this isn’t possible, inform the contractor of any access problems so they can bring a tanker with a powerful pump and extension pipes to suck the sludge from the tank over the distance. 

Difficult roads

Rural areas often have narrow country lanes or steep hills. Let the contractor know in advance so they can bring the right vehicle. Many companies have small tankers or towable trailers for use with a 4×4 such as a LandRover or similar.

Size of tank

The capacity of your septic tank determines the time needed to empty the tank and the vehicle size sent to the job. This factor, in turn, determines the size of your bill.

Tank CapacityTime to Empty
4,500 L45 minutes
8,500 L60 minutes
12,500 L90 minutes
17,500 L150 minutes

These durations represent average times and will vary depending on various factors.

Although large tanks take longer to empty and cost more, it’s worth remembering that they also need emptying less often. Therefore, although the initial cost to buy and install a large septic tank is more expensive, it will save you money in the long run.

The Type of Tank

You must also consider the type of tank you own as another factor. 

  • The number of chambers – single chamber tanks are cheaper to empty than multi-chamber tanks.
  • Material – tanks made from GRP or PE are cheaper to empty than brick or concrete. Their smooth surfaces and rounded corners collect fewer solids and require less backwashing. 

Backwashing or Inspection

Most customers only require a tank emptying service. However, sometimes you might want your tank cleaned and inspected, mainly if the septic tank isn’t operating correctly and you suspect a blockage or leak. But, as you’d expect, these services cost extra.


Certain parts of the UK have a higher cost of living than others. Areas in the South of England have higher wages than those elsewhere in the country. Often, the hourly labour rate can vary by £4-£8/hour

As we’ve already stated, you’ll find most septic tank systems in rural areas where it’s too expensive for the local water company to install mains drainage. Furthermore, these areas have a lower average wage than those nearer cities or suburbs.

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How Often Should We Empty The Tank?

The emptying frequency depends on the tank size and the number of people living in the house. Generally, empty a septic tank every year if you have a small to medium-sized household. But usually, we can empty a tank serving a larger property with fewer people every two years.

Regular emptying is essential if you want your septic tank to operate correctly, and everyone wants that.

Over time the wastewater and slurry that came from the house into the tank separate into three layers:

  • Scum – The topmost layer consists of oils, fats and other lighter than water substances, solidifying into a floating crust.
  • Wastewater – This middle layer consists of wastewater with suspended solids left over after the scum separates and solid waste settles. Wastewater and some suspended particles run through the soak-away system of pipes and percolate into the surrounding soil, known as the drainage field.
  • Sludge – This section consists of the settled solids that drop to the bottom. Over time, this layer builds up, and a licenced waste haulage contractor must eventually remove it. Leaving the sludge in place restricts the particles’ settlement distance, and there’s nowhere for the wastewater to separate. Then, the sludge gets into the wastewater distribution system, and you have foul odours and sludge pooling on the surface of the drainage field. It’s then that the system breaks down.

Even if the tank isn’t full, which often happens when you have a large tank, it’s good practice to empty it regularly to keep the bacteria active. Healthy bacteria help digest the sludge and ensure the system works properly.

What’s Involved In The Job?

If the toilets in your property flush slowly, drains and sinks take longer to empty, and you notice a foul odour around the septic tank or wastewater drainage field, it’s time to have the tank emptied. The tank is full and struggling to cope with the extra waste. And if not addressed quickly, the septic tank will stop working, and the drainage field will become unusable. Therefore, arrange for the sludge tanker to arrive as soon as possible.

The following describes a typical sequence of events. Details might vary depending on the type of tanker and septic tank:

  1. The contractor connects a large diameter flexible pipe to the pump situated on the vehicle.
  2. Drop the pipe’s other end into the septic tank’s access hatch.
  3. Pump the scum crust and sludge into the tanker, leaving as much wastewater as possible in the tank.
  4. Sometimes, the contractor backwashes the tank with clean water to dislodge any solids that have become stuck to the tank’s inner surface. This is especially important if it’s a masonry or concrete tank with rough surfaces and sharp angular corners.
  5. The contractor then takes the tanker to a sewage treatment facility which sterilises and disposes of the contents according to the existing waste disposal legislation.
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DIY or Professionals

Emptying a septic tank is something that an amateur must not do. Raw sewage is a dangerous material due to the presence of various micro-organisms hazardous to health. Furthermore, uncontained raw sewage will damage the local ecosystems and open water supplies. Polluting the environment in this way is illegal and very expensive to remedy. The new Septic Tank Regulations, which came into force in 2015,  state that wastewater from septic tanks must not drain directly into water courses, Instead it must be:

  • Replaced by a small sewage treatment works certified to BS EN 12566-3.
  • Or diverted to a drainfield designed and built according to BS 6297 2007.

Property owners had to upgrade their existing septic tank systems by 1 January 2020. The complete regulations appear on the UK government website. But, it’s easier to read about septic tanks and sewage treatment plants on this UK government page. You will also find that all new septic tanks and upgrades need appropriate Planning Permission and compliance with Approved Document H of the Building Regulations

If you’re a DIYer, you must not carry or treat wastewater because of the following requirements:

  • Highly technical knowledge.
  • Specialist health and safety training.
  • Numerous regulations you must know.
  • Waste carriers must register with the Environment Agency.
  • Only a licenced professional company can hold the necessary permits.

You can see why attempting waste carrying or treatment is impossible if you’re an amateur. Instead, it’s more cost-effective to hire a professional who already has the training, is certified, and holds all the appropriate permits and licences.

Find A Local Pro

Emptying a septic tank is not a DIY job. Instead, hire a fully trained professional who already holds the permits and licences required under UK law. Complete the form on this page, and you will receive up to four septic tank emptying quotes from fully licenced contractors.

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