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Septic Tank Costs: Installations, Emptying and Replacements

| Michael Quinn

How much does a septic tank cost?

An onion shaped septic tank
An onion shaped septic tank.

Our charge for carrying out the supply and installation of a new septic tank will start from £5,000+VAT, including the costs of labour and all plants and materials needed. This price will also be subject to the availability of access, as well as ground conditions. If you need a test hole survey, or there are services in the area, you wish to carry out the work; this will further impact your septic tank’s installation cost.

What affects septic tanks costs?

A few of the core factors that will affect your septic tank cost will be:

  • the size of the tank itself
  • the ground conditions where it's being installed
  • the access to the site
  • the size of the drainage field required to suit the tank

You will also find that the size will affect how much it costs to empty your septic tank. Larger tanks may require more than one load, which means the price will increase.  

How much does it cost to run a septic tank?

How much it will cost to run a septic tank on your property will depend on several different factors:

  • Size of the tank
  • Location of the tank
  • Usage of the tank (the more people using it, the quicker it will fill up and the more expensive it will be to run)

These factors will combine into the cost of running a septic tank over the course of a year, as they all affect your septic tank’s emptying cost, as well as any maintenance that is needed.

Our estimates for land drains for septic tanks.

Our prices for the installation of land drainage that will be connected to your septic tank are based on a couple of different factors:

  • Good access for all supplied plant machinery
  • Percolation test results
  • The size of the tank and the number of people it is serving
  • The depth of the drainage field installation

Surface water warning

If surface water or rainwater can enter your septic tank, either through open joints in your drains, broken pipes or from a direct connection through a downpipe from your property’s guttering, this can cause problems with the separation of waste in your septic system.

This is because water that enters in a surge, such as during heavy rainfall or a storm, can stir up the first chamber's contents in the tank. It can also bypass separation barriers, disturbing any settlement that has already taken place in the primary settlement chamber. This may increase the cost of having your septic tank pumped because the excess water may not drain correctly, having not allowed solid waste to settle.

Why is rainwater problem?

If solids are getting through to the next chamber, they can reach your soakaway system, which could result in clogging and reduce the lifespan of your drainage field.

If you believe this may be happening in your system, we highly recommend that you book a CCTV drain survey with ASL, to discover the source of your drainage problem. We use a state-of-the-art flexible camera to take detailed footage and images of the inside of your drains, spotting any flaws, faults or damage that may be causing your drains not to work correctly.

If the cause of your drainage problem is discovered this way, we will be able to repair the drain for you. If the cause is not found in the drain, we will suggest that your surface water gullies and downpipes are tested, to see if the problem can be found.

How septic tanks work

Septic tanks work through three significant processes.

These are the initial separation of solids from liquids, the limited bacteriological action, and finally, absorption. A septic system should always have a minimum of two chambers (or occasionally, a single chamber divided by a separation wall with dip pipes). Effluent will enter the tank, where the initial separation of larger solids takes place, and fats float to the surface. Because the first chamber receives waste straight from the drains, the contents can get stirred up as new effluent enters, especially if it is a large volume all at once, such as emptying a bath. This is why the first chamber is limited to the initial separation of larger solids and fats. 

Effluent will then pass via the dip pipes to the second chamber (or additional chambers), which offer a calmer environment. Smaller particles of solids in suspension will also have the opportunity to settle at the bottom of the tank. While this process takes place, there is a limited bacteriological breakdown of the effluent. The separated effluent then passes along a further dip pipe to the land drains. These are installed in light aerated soil. The separated liquid will be absorbed by the surrounding soil, providing a secondary level treatment to the wastewater and acting as a supplementary natural filtration.

How do dip pipes work?

Dip pipes are essential to the separation process, as, without adequate separation, suspended solids and fats can pass through the septic tank, and on through to the soakaways. There, they can coat the surface, causing irreparable damage and making it progressively waterproof. This will diminish the soakaway’s ability to dissipate water until it ceases to work altogether.

To learn more about septic tanks, costs and how they work, or to get your septic tank cleaned or repaired, call us today. As experts in the drainage industry, we will be able to help explain any part of the process in the tank and send our experienced engineers to assess your septic tank.

Costs for test hole surveys

Before we begin any work on your property, we will carry out a test hole survey as part of the work. This survey will help us find out how porous or firm the ground of your property is, then determine where it is possible to install a septic tank, sewage treatment plant, or drainage field.

Prices for a stand-alone test hole survey can range from £150 to £1,500 depending on:

  • your ground conditions
  • the type of survey required
  • and access to the site


Contact us if you would like to know more about our test hole surveys and percolation tests and how we carry them out. If you have been looking for a cost-effective and efficient septic tank at a price that will suit your budget, get in touch with ASL Limited.

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