Pipe Relining Case Study in Hatfield School

Client Challenge

The school estate manager responsible for a ablution block drainage line in Hatfield, Pretoria needed a repair option that avoided unnecessary excavation. The reported issue was capacity loss during heavy rainfall, with the main operational risk being student disruption and repeated blockages.

The affected route was located under a concrete slab. That made open trench replacement more disruptive than a controlled diagnostic and trenchless rehabilitation approach.

CCTV Inspection Findings

HydroTrace would first verify the pipe internally before recommending relining. In this scenario, CCTV inspection indicated open joints allowing silt and groundwater to enter the line. The host pipe was recorded as 110 mm concrete, with approximately 64 m requiring close assessment.

The inspection focus included pipe grade, deformation, connection points, water holding, silt deposits, joint condition and whether the host pipe was suitable for a liner or coating system.

Existing Pipe Details

• Pipe material: concrete
• Internal diameter: 110 mm
• Assessed length: 64 m
• Access restriction: under a concrete slab
• Failure mode: stormwater infiltration

Recommended Rehabilitation Method

The selected approach was ambient-cure CIPP liner. This method involves resin-impregnated liner installed from existing access points and cured in place. It was selected because it could reinstate the internal pipe surface while limiting demolition, downtime and reinstatement cost.

Preparation included jetting, silt removal and post-cleaning CCTV survey. Preparation is critical because relining should never be installed over loose scale, grease, silt or unverified obstructions.

Installation Process

1. Confirm access points and isolate the working section.
2. Perform CCTV inspection and mark the affected distances.
3. Clean the pipe using jetting, descaling or mechanical cleaning.
4. Reinspect the pipe to confirm readiness for rehabilitation.
5. Install the ambient-cure CIPP liner to the measured section.
6. Allow the system to cure or set under controlled conditions.
7. Carry out post-installation CCTV and flow verification.
8. Issue a technical report with findings, photos or video references where available.

Project Outcome

The intended outcome was to restore flow, reduce water ingress, seal the damaged pipe wall and avoid unnecessary excavation around the ablution block drainage line. The estimated working window for this scenario was 2 days, depending on access, cleaning difficulty and curing requirements.

For similar sites in Hatfield and Pretoria, HydroTrace would recommend combining CCTV inspection, cleaning and post-repair verification so the client receives a defensible technical record instead of a guess-based repair.

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FAQs

Why was pipe relining considered instead of excavation?

Relining was suitable because the damaged section was accessible from existing inspection points and excavation would have disrupted the site, finishes or operations.

Was CCTV inspection used before the relining decision?

Yes. CCTV inspection is used to confirm pipe condition, locate defects, measure distances and verify whether the line can be cleaned and rehabilitated internally.

Can this method work below concrete or paving?

Yes, where the host pipe still has enough structural profile and access is available, trenchless lining can rehabilitate sections below concrete, paving, roads or buildings.

Is pipe cleaning required before lining?

Yes. Jetting, descaling or mechanical cleaning is required so the liner or coating bonds against a prepared internal pipe surface.

What confirms that the repair worked?

Post-installation CCTV, flow verification and where applicable pressure or water testing are used to confirm the result.