Case studies

Raising and Sealing MH’s with Cretex Pro-Ring™

Located on the shore of Lake Macquarie this Hunter Water Corporation MH is subject to tidal influence. The lid and frame were in extremely poor condition and during high tides, subject to salt water ingress.

Unwanted water entering the sewer network (due to rain, sea water or ground water) through cracks, damaged grade adjustment rings and failed mortar results in unnecessary treatment costs. The increased flow causes excessive wear and tear on pump stations, treatment plants and the increased risk of sewer overflows results in unnecessary costs to water authorites and can risk the environment.


MH at low tide showing broken frame and lid removed

Hunter Water Corporation selected Cretex Pro-Ring™ to raise the height of this manhole and seal it to prevent ongoing water leakage.

Cretex Pro-Ring™ was selected for it’s light weight, high durability and it’s good resistance to hydrogen sulphide gas and leakage. The light weight Cretex Pro-Ring™ minimises this risk of injuries associated with manual handling of heavy concrete rings.

Two 150mm high Cretex Pro-Ring™ were used to raise the frame and cover a total of 300mm. The Cretex Pro-Rings™ 24”ID x 36”OD were used with a 6” (150mm) Grade ring installed first and a 6” (150mm) Finish installed prior to positioning of the new frame and lid.

As this installation is above ground and subject to tides and wave action, it was decided that, in addition to the ChemLink M1 structural adhesive/sealant, threaded rods would also be anchored into the existing shaft with the frame and Pro-Ring™ bolted down.

Operators were able to quickly and easily install the Cretex Pro-Ring™ providing a long term and cost effective solution.

MH showing threaded rods with 1 Pro-Ring™ Grade ring installed

MH showing Pro-Ring™ Installation complete with new lid and frame

MH with Pro-Ring installed and mortar used for visual appeal over Frame edge


Failed and leaking risers


Cretex Pro-Ring™