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The Newton CDM System is a Type C waterproofing solution that comprises of BBA-certified cavity drain membranes, drainage channels, pumping systems and pumping ancillaries that are all specifically designed for waterproofing and protecting earth-retaining and below-ground structures against water from the ground.


Type C Systems differ from Type A and Type B waterproofing in that they do not seek to resist the water pressure, but instead allow it to enter before depressurising and controlling it in a safe fashion that will keep it away from the internal space.

BS 8102:2022 states that where a combination waterproofing design is being considered, systems should have different performance characteristics to mitigate the risk of failure due to a common cause. The compatibility of the different protection types should also be assessed in order to minimise the risks and negate the need for remedial measures.

So, where the assessed risks are deemed to be high or where the consequences of failure to achieve the required internal environment are deemed too high, Type C systems truly offer a failsafe system.

type c waterproofing system

Type C System Maintenance

Key Considerations

Type C solutions such as the Newton CDM System actually require very little maintenance, however there are a number of points that you should be aware of, and indeed you should make your client aware of these points in the content of your survey report and/or contract documents.

The Type C system should be designed and installed as a maintainable waterproofing management system, and as such the vital components should be accessible for both inspection and maintenance. This is highlighted as a key requirement within the British Standard for waterproofing, BS 8102:2022.

PLEASE NOTE: this guidance document does not provide detailed information on how the servicing visits should be scheduled or performed. The specific site conditions, waterproofing design, materials, and the machinery used will all play a part when deciding on the frequency and scope of your service visits.

During Installation

Silt build up in cavity drain waterproofing

Whilst installing the system, any repairs that are required should be carried out as and when they occur. This will save time later and reduce the risks of overlooking potential problems.

Once the system is installed, and before the finishes are applied, the membrane should always be checked for damaged area and repaired where necessary. Cavities, drainage channels and sumps are all susceptible to build-ups of silt, fines and other particulate matter that may enter the building along with water from the ground. The deposit of calcium carbonate (free lime) can also occur in circumstances where new concrete is used in the construction, or chalky soils exist in the substrate. In both instances, severe deposits can result in the failure of a Type C System, as shown in the image to the right.

Inspection Ports

To combat such occurrences, drainage channels should be fitted with accessible and structurally capable inspection ports that allow for the drainage channels to be inspected, jetted or washed as necessary.

It is important that these inspection ports are situated in practical and convenient locations in order to allow for periodic access, inspection and cleaning as and when required in future, and these locations should be detailed on the installers final floor plan.

As a minimum requirement, inspection ports should be large and accessible enough that:

  • The water levels within the channels can be seen
  • A cleaning nozzle can be inserted and directed in both directions as required
  • A camera can also be inserted in order to allow for inspection in either direction

Sump & Pump Chambers

Sump chambers should also be installed in locations that allow for easy access during the periodic servicing schedule.

Pumps and the associated pipe work within the sump chamber should be accessible when the sump is open, and installed in such a way as to allow easy servicing and wherever necessary the easy replacement of elements of the pumping system.

Maintenance Inspections 

inspection ports for cavity drain membrane

The pumping system should have its first service within 3 months of being commissioned, and at this first visit a future service schedule should be agreed between the service engineer and the client.

The servicing and maintenance of Type C systems should be carried out by trained, competent service engineers, with a good knowledge of Type C waterproofing and access to the specific details of the installed system.

The maintenance inspection should cover all of the following areas plus any additional requirements, as detailed by the specific pump manufacturer:

  1. Cleaning and descaling of the pump system as required
  2. Checking for and ensuring free movement of the pump impeller
  3. Checking pump seals for leakage and renewing as required
  4. A pump impeller test ensuring free movement
  5. Inspect pump discharge pipes for damage and leaks
  6. Check non-return valves
  7. Remove any debris from the base of the sump that may interfere with pumping
  8. Check electrical connections and fuses
  9. Flush through the Basedrain and Floordrain drainage system (if required)
  10. Check the positioning of the battery
  11. Record the internal environmental temperatures
  12. Check battery terminal connections
  13. Check battery Volts
  14. Check the inverter and inverter settings
  15. Check the battery in alarm and test
  16. Check connections to panel systems (if installed) and test
  17. Check pump Amps
  18. Check pump cable resistance

PLEASE NOTE: Sump pumps are electrically powered, so it is important to maintain a constant power source in order to achieve maximum drainage capacity. Newton Victron Power Inverters are available for continuing the discharge of the sump during failure of the mains power supply.

Please contact the Newton Technical Team or the installing contractor for information relating to the servicing of individual pumps and specific configurations.

Service Intervals

At first, Type C systems should initially be inspected and serviced at least annually, however in some circumstances the period between services may be considerably shorter or longer. Site conditions, design, materials, the machinery used, and the severity of the implications of a system failure will all play a part when deciding on the frequency and scope of service visits.


For more information on this technical article, or to speak to our Technical Team, please call 01732 360 095, email tech@newtonwaterproofing.co.uk or fill out the form below.

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