Underground storage tanks

Combined sewer Overflow

Camplas Technology specializes in the design and manufacture of Combined Sewer Overflow (CSO) tanks, offering robust solutions for efficient stormwater management. Our tanks can be fabricated with capacities up to 300m³, and for projects requiring larger volumes, they can be seamlessly joined together to achieve virtually unlimited capacity. These tanks are engineered to handle the excess flow during heavy rainfall, preventing the overload of sewer systems and minimizing environmental impact. With a focus on durability, reliability, and ease of installation, Camplas Technology’s CSO tanks are the ideal choice for managing wastewater and protecting urban infrastructure.

3 x 300m3 combined sewer overflow tanks for Welsh Water- Nelson
6 x 200m3 combined sewer overflow tanks - Dt Andrews Golf Club
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Combined Sewer overflows


Click on the link below to download the underground storage tank data sheet

Designed to contain overflows to control waters at times of heavy rainfall or other events which are beyond the capacity of the treatment system.

Gravity or pumped discharge return and can be fitted to consented discharges to reduce the impact on the environment or to prevent non-consensual discharges, which could result in prosecution under the water resources act. 

  1. Regulator CSOs: These are the most common type and use mechanical devices such as gates or weirs to control the flow of combined sewage. During heavy rainfall, the excess flow is diverted to overflow points while the rest continues to the treatment facility.

  2. Outfall CSOs: These are specific points where the overflow from combined sewers is discharged into water bodies. They are designed to manage the volume and rate of overflow to minimize environmental impact.

  3. Storage CSOs: These involve the use of storage tanks or tunnels to temporarily hold the excess combined sewage during peak flow periods. The stored sewage is later pumped back into the sewer system when the flow subsides, reducing the frequency of overflows.

  4. In-line CSOs: This type of CSO involves modifications within the existing sewer pipes, such as installing flow control devices or additional piping to manage the overflow within the sewer network itself.

  5. Off-line CSOs: These systems involve diverting overflow to separate storage or treatment facilities located off the main sewer line. This helps in managing peak flows without overwhelming the main treatment plant.

  6. Screening CSOs: These systems include mechanical or static screens to remove solids and debris from the overflow before it is discharged. This helps in reducing the environmental impact by preventing the discharge of untreated sewage solids.

Using a Camplas GRP (Glass Reinforced Plastic) combined sewer overflow (CSO) tank offers several advantages over polyethylene or steel tanks, making it a superior choice for managing stormwater and combined sewage flows. Here are the key benefits:

  • Corrosion Resistance: No rust, withstands harsh chemicals.
  • Lightweight & Strong: Easy to transport and install, high structural integrity.
  • Flexible Design: Custom-molded to fit specific site requirements.
  • Durable: Withstands a wide range of temperatures and conditions.
  • Leak-proof: Seamless construction reduces the risk of leaks.
  • Low Maintenance: Smooth internal surface, easy to clean.
  • Cost-effective: Lower long-term costs, reduced risk of leaks.
  • Eco-friendly: Long service life, lower environmental footprint.

13,000 SuperTanks now in service installed worldwide

BS4994-1987(formerly BS4994-1973) with a minimum factor of safety of 8/1

Available in various sizes and diameters. Ranging from 20m3 to 300m3 in one tank.

Key features of the Combined Sewer Overflow Tanks

High strength helically wound composite construction

One piece construction with no joints or seams below the liquid level

Designed to hold corrosive chemicals up to a specific gravity of 1.35

Unaffected by U.V. degradation and very low temperatures
Tensile strength 20 times higher than Polyethylene
Combined sewer overflow

Problem: Overflowing Car Park and Sewage Discharge



The Royal & Ancient Golf Club at St. Andrews faced car park overflows during heavy rainfall, leading to unpleasant sewage discharge into St. Andrews Bay.

Solution: Installation of Overflow Attenuators

We installed six combined sewer overflow attenuators beneath the car park, each 3.5 meters in diameter and 22 meters long, providing a total capacity of 1.2 million liters.




  • Minimized Residue: Tanks designed to prevent septic conditions.
  • Odor Control: Ozone injection combats smells.
  • Logistical Success: Navigated narrow streets, including ‘Ochterlonies Corner,’ for timely installation.



This solution was completed in time for the British Open, effectively resolving the overflow issue and enhancing the visitor experience.

Contact us about Combined sewer Overflow

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