Septic tanks

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Discover the simplest way to protect your property and the environment with our range of compact Rewatec septic tanks.

Premier Tech range of Rewatec septic tanks

What is a septic tank?

A septic tank is an underground system that receives and partially treats raw wastewater from domestic or commercial properties not connected to the main sewage system, such as those in rural areas. They are typically the most simple and most economical form of onsite wastewater treatment (known as primary wastewater treatment).

CALONA Rewatec septic tanks

With nominal capacities from 3,000 up to 250,000 litres, our Rewatec septic tanks (formerly Conder millennium septic tanks) are ideal for virtually any application. Quick to install, simple to use, and easy to maintain, these durable solutions give you a discreet and reliable performance you can trust.

Our septic tanks are also CE and UKCA marked having been fully tested and certified to EN12566-1.

Properties owners, please note: as per the building regulations, a standard septic tank that discharges to surface water, no longer complies with UK regulations (2020 General Binding Rules). However, our septic tanks can be installed if you apply for a permit and it is approved by the Environment Agency. Our septic tanks can also be installed as part of a larger sewage treatment system (for example with our Ecoflo wastewater treatment system for energy free wastewater treatment).


Example applications

  • primary residences
  • seasonal residences
  • residential developments
  • apartment buildings
  • campsites and parks
  • office buildings
  • commercial sites
  • schools

How does a septic tank work?

CALONA millenium stockage

Wastewater from your domestic property runs into a main drainage pipe that flows into the septic tank. The septic tanks job is simple: it allows wastewater to separate into three layers.

In the top layer, oils, greases, and fats float to the surface and form scum. In the bottom layer, solids settle on the bottom of the tank and form sludge. Periodic emptying by a licensed waste disposal company is required to remove the gradual build-up of scum and sludge.

Partially clarified liquids accumulate between the layers of scum and sludge and exit the septic system through the outlet pipe. An integrated effluent filter - standard in all 3,000-10,000 litre polyethylene Rewatec septic tanks, capture suspended solids that could clog system components further downstream.

Wastewater final dispersal

As the effluent is not fully treated, wastewater can flow into an advanced secondary system for additional treatment (Ecoflo, MBBR, or SBR) to meet the the general binding rules set out by the Environment Agency and to fully protect our environment.

In areas where the septic tank does not discharge directly to a watercourse, the effluent can leave the septic system and flow into an array of perforated pipes (i.e. a septic drainage field or leach field) for further treatment before discharging to the ground. Please note, a percolation test must be carried out before discharging to a drainage field to ensure the porosity of the soil is adequate.

Will a septic tank work without power?

The short answer is yes, a septic tank will work without the use of electricity. In fact, one of the benefits of a septic tank is that it is a self-contained wastewater treatment system that uses natural processes to treat and dispose of wastewater from your household. This means that it does not require electricity or chemicals to operate, making it a cost-effective option for households that are not connected to the main sewage system.

If you don't have space to install a drainage field downstream of your septic tank, or if gravity alone isn't sufficient to transport the effluent to your drainage field, a pump station may be required. This will require electricity for use.

Septic tank servicing and maintenance

Protect your investment in your Rewatec septic tank by having it regularly serviced and maintained. When we visit your property we will :

  • inspect your septic tank and check for cracks and leaks
  • measure the scum and sludge layers
  • advise on desludging if required (see below for more information)
  • clean the effluent filter in the outlet pipe
  • keep and update maintenance records for your system
  • carry out any repairs to your septic tank (if required)

Do septic tanks need emptying?

Yes, septic tanks do need to be emptied on a regular basis. Over time, solid waste and other debris will build up in the tank, reducing its efficiency and causing problems such as sewage backups in your house and overflows in your garden. Depending on the size of your tank and the amount of wastewater it receives from your household appliances, it may need to be emptied every few years, every year or more frequently.

It is important to have the septic tank pumped / desludged and cleaned by a licensed professional to ensure that it is working as it should, and to prevent any potential health or environmental hazards in the future. If you currently own a septic tank and require it emptying, contact us and we can assist with your requirements.

Obtain a free quote for our services

Our septic tank warranty

For over 50 years, we have proudly developed sustainable and long-lasting products that make a real difference for our customers, our professional partners, and, above all, our planet.

Our experience in the industry allows us to give you a complete warranty for septic systems.

Our Rewatec septic tank warranty includes:

  • 10 year shell and construction (polyethylene)
  • 25 year shell and construction (GRP)


CPD training course

Our 45-minute CPD certified course "An introduction to off-mains wastewater management" is ideal for Architects, Consultants, Engineers, Installers and Specifiers looking to learn more about what wastewater treatment is and why it is important, regulatory bodies and the current UK regulations, how systems are designed, and what systems are available.

Request a CPD course

Options and accessories

Personalise your septic tank to meet your site requirements, with our wide range of options and accessories.

Polyethylene septic tanks

Options and accessories for Rewatec septic tanks (3,000 and 4,000 litres)


GRP septic tanks

Options and accessories for GRP Rewatec septic tanks

Technical information

Our standard range of polyethylene septic tanks are available in 3,000 to 10,000 L capacities, whilst our glass reinforced plastic (GRP) septic tanks are available in 14,000 to 84,000 L capacities. If you have a need for a larger septic tank, please contact us for a bespoke solution that meets your requirements.

Polyethylene septic tanks

Rewatec septic tank specification table


GRP septic tanks 

Rewatec GRP septic tank specification table

Available products

We offer a complete range of septic tanks to meet your needs from 3,000 litres to 250,000 litres. Wherever your site, whatever the regulations, we have the right product to transform any wastewater treatment challenge into a tailor-made solution.

UK lake on a sunny day

Free quote

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