Septic Tanks & Cesspools

Clearwater units are available in two shapes, spherical and cylindrical, with sizes suitable for all domestic applications.

Clearwater septic tanks are designed to meet both the installation requirements and the standards of discharge specified by EN 12566 Part 1.

Clearwater tanks are used for domestic sewage disposal where connection to a mains sewer is not practical.

The septic tanks in the range all achieve a high degree of settlement, producing a quality of effluent for discharge to a land drainage system.

Septic Tanks & Cesspools

A septic tank consists of a single chamber system that retains sewage from a property for sufficient time to allow the solids to form into sludge at the base of the tank, where it is partially broken down through anaerobic digestion. The remaining liquid in the tank then overflows from the tank by means of an outlet pipe to a drainage field.

Cesspools are designed for storage only, with their contents being emptied at regular intervals using tankers. High Level Alarms with audible and visual warnings are available for all tanks to enable level monitoring for optimum use.

When sizing a storage tank for domestic properties it must be noted that under the Building Regulations it must have a minimum capacity of 18,000 litres (2 people) under Environment Agency regulations.

When siting units there are a number of factors to be considered. Systems should not be positioned closer than 7 metres to any dwelling and as far as possible from any watercourse, normally not less than 10 metres. Adequate access to tankers for emptying should also be taken into consideration.

Shallow Dig Septic Tank

Clearwater offers septic tanks suitable for shallow dig installation and designed to reduce both installation time and costs.


  • Reduced installation costs – less soil disposal and excavation costs.
  • Manufactured from GRP and EN12566-1 approved.
  • 99.7% efficient.
  • Suitable for pea shingle gravel backfill for dry sites
  • Fully CE-marked


No. People
(150 Ltrs/
Invert Height
STH028 2800 5 1225 2955 500
STH038 3800 12 1225 3895 500
STH057 5700 24 1425 4275 500
STH071 7150 34 1920 3225 500
STH091 9150 47 1920 3960 500

Spherical Septic Tank and Cesspool Selection Chart

Spherical septic tanks are manufactured as standard from 2,800 to 4,600 litres net working capacity.

Cylindrical cesspools are available with capacities from 18,000 to 26,000 litres. The cylindrical tank allows reduced depth excavation in comparison with the same size of spherical tank, offering considerable savings where ground conditions are difficult or where there is a high water table.



Septic Tanks (Spherical) Cesspools (Cylindrical)
Diameter A
Height B


Diameter C
Length D


2,800 STS0281OB 615 1,905 2,565
3,800 STS0381OB 835 2,070 2,795
4,600 STS0461OB 1011 2,080 3,035
18,000 CP2818S10CB 4,000 2,600 4,320
22,000 CP2822S10CB 5,000 2,600 5,090
26,000 CP2826S10CB 6,000 2,600 6,190

Septic Tanks have a 1.0m standard invert depth. 1.5m inverts are available upon request.

Cesspools are available with invert depths of up to 2.0m. For deeper cesspool inverts please contact our technical sales team.



Storage Tanks

Clearwater storage tanks provide a reliable solution for the collection and retention of:

  • Surface water;
  • Firefighting reservoirs;
  • Rainwater harvesting reservoirs;
  • Animal drinking reservoirs.

* For silage storage, please inquire.