No-Dig Drain Repair: Patch Lining, CIPP Full Relining, Resin Injection and Lateral Relining Methods

Summary

Traditional drain repair meant digging up the garden, driveway, or road — expensive, disruptive, and slow. No-dig (trenchless) technology allows the same repairs to be completed from access points at either end of the drain, typically within a few hours and at a fraction of the excavation cost. The market has matured significantly: CIPP relining now routinely achieves a 50-year design life when properly installed and is used by all major UK water companies for sewer rehabilitation.

No-dig repair is not always appropriate. Collapsed pipes with zero bore, severely displaced joints, or drains with tight bends that prevent liner insertion may still require excavation. A CCTV survey (see drain cctv survey) is essential before specifying any no-dig method — choosing the wrong technique for the defect type wastes money and may not solve the problem.

For domestic drainage contractors, understanding the no-dig toolkit is increasingly essential. Householders expect it, insurers prefer it, and local authorities mandate it for works under adopted roads. The cost premium over excavation has largely disappeared for pipes up to 150mm diameter over runs of more than 5 metres.

Key Facts

• BS EN 13566-4 — structural design and installation of plastics piping systems for renovation of drains and sewers (CIPP standard)
• CIPP design life: 50 years minimum when installed to BS EN 13566-4
• Minimum pipe diameter for CIPP: 100mm (some specialist contractors work down to 75mm)
• Typical liner thickness: 3–6mm for 100–150mm pipes; 6–12mm for 150–300mm pipes; custom calculation for larger
• Patch liner length: typically 0.5m, 1.0m, or 1.5m standard sizes; custom lengths available
• Resin systems: polyester (most common, lowest cost), vinylester (chemical resistance), epoxy (best mechanical properties)
• Curing methods: ambient temperature (overnight), hot water, UV light (fastest, 20–40 minutes)
• Bypass pumping: required if drain is in active use during relining
• Lateral launch: robotic lateral lining can install a junction liner from inside the main pipe — eliminates excavation for branch connections
• Patch lining structural requirement: patch must overlap defect by minimum 150mm either side
• Post-installation CCTV: mandatory to verify full cure, no wrinkles, no bypass of defect

Quick Reference Table

Detailed Guidance

CIPP Full Relining

CIPP (Cured-In-Place Pipe) is the gold standard for no-dig pipe rehabilitation. A felt or fibreglass liner tube is impregnated with resin, inverted or pulled into the host pipe, then inflated with air or water bladder to press against the pipe wall and cured to form a structural pipe within a pipe.

Process:

1. Pre-clean by high-pressure jetting (typically 3,000–4,000 psi)
2. Pre-installation CCTV to confirm suitability and document existing condition
3. Calculate liner specification (thickness, resin type) based on pipe diameter, burial depth, and loading
4. Install liner using inversion drum (water or air pressure) or pull-in-place winch
5. Inflate calibration hose inside liner to hold against pipe wall
6. Cure: ambient cure (6–24 hours), hot water cure (1–3 hours at 60–80°C), or UV cure (20–40 minutes)
7. Cut out laterals with robotic cutter
8. Post-installation CCTV and pressure test

UV curing has become the dominant method for 100–300mm pipes. UV light travels down the liner on a light train pulled through at 0.5–1.0 m/min. Total installation and cure time for a 20m domestic drain: typically 3–4 hours.

Liner thickness calculation per BS EN 13566-4:

• Inputs: pipe diameter, burial depth, soil conditions, traffic loading, groundwater level, pipe ovality
• A 100mm pipe at 1.0m depth in domestic ground with no traffic loading typically requires 3mm liner
• For structural purposes (pipe fully deteriorated, liner must be self-supporting) thickness increases significantly

Patch Lining

Patch liners address isolated defects — a single cracked joint, one section of cracked pipe, a displaced joint — without relining the entire run. The patch is a short section of GRP (glass-reinforced plastic) or resin-impregnated felt, installed on an inflatable packer.

Process:

1. Clean the area to be patched
2. Insert packer assembly to chainage of defect
3. Inflate packer to press patch against pipe wall
4. Cure (ambient or UV — UV patches cure in under 10 minutes)
5. Deflate, withdraw packer
6. CCTV to inspect patch

The patch must extend a minimum 150mm beyond the defect in each direction. For a single open joint (typically 10–20mm wide), a 500mm patch is usually sufficient. For a cracked pipe section up to 300mm long, a 1,000mm patch.

Patch lining is only suitable for isolated defects. If CCTV shows defects every 2–3m along a run, full CIPP relining is more cost-effective than multiple patches.

Resin Injection (Joint Sealing)

Resin injection is a non-structural technique for sealing joints against groundwater infiltration. It does not address structural defects (broken pipes, displaced joints). The process uses a dual-port packer that isolates a joint, injects a flexible polyurethane or acrylic resin, and allows it to cure to form a water-stopping gasket.

Suitable for:

• Grade 2–3 open joints with infiltration (DIS/DIF codes on CCTV survey)
• Post-CIPP joint sealing where small gaps remain
• Sealing around lateral connections

Not suitable for:

• Joints open more than 25mm (insufficient material contact)
• Structurally displaced joints (BJD Grade 4–5)
• Broken pipe sections

Lateral Relining

When CCTV reveals a failed junction between a branch pipe and the main drain, the traditional repair was to excavate at the junction point. Lateral relining uses a robotic launcher inside the main sewer to install a junction liner that seals the junction and extends up the lateral for 1–3 metres.

The process:

1. Main drain CCTV to identify junction location (chainage from access point)
2. Clean main drain and lateral
3. Deploy robotic launcher to junction chainage
4. Insert pre-impregnated lateral liner into robotic arm
5. Rotate arm into lateral and inflate
6. Cure (UV or ambient)
7. Pull back and CCTV to verify

Lateral relining is especially valuable in situations where excavation would be through a driveway, wall foundations, or road — where the access cost would dwarf the repair cost.

Pipe Bursting

Pipe bursting is not strictly a lining method but is classified as no-dig. A conical bursting head is pulled through the existing pipe, fracturing it outward and simultaneously pulling in a new HDPE pipe of the same or larger diameter. Requires a small pit at each end for equipment access and pull-back.

Best suited to:

• Completely collapsed clay or concrete pipes where lining is impossible
• Where the client wants to upsize the drain
• Straight runs with no tight bends

Not suitable for ductile iron, steel, or heavily reinforced concrete pipes.

Frequently Asked Questions

Is CIPP relining as strong as a new pipe?

For new lining over a structurally sound host pipe, the liner is effectively an inner pipe with the host providing external support. For structural (fully deteriorated) pipe design — where the liner must be self-supporting — BS EN 13566-4 calculations ensure the liner alone can withstand soil and traffic loads. A properly installed 50-year design life CIPP liner regularly outlasts adjacent new-build pipes in practice.

Will relining reduce the pipe's internal diameter?

Yes, slightly. A 3mm liner in a 100mm pipe reduces the internal diameter to approximately 94mm. Hydraulic capacity is also affected — ADH Table 1 uses the actual bore, so a relined 100mm drain may have slightly reduced DU capacity. In practice, for domestic drains with moderate loading, this reduction is insignificant. For heavily loaded commercial runs, check the hydraulic capacity post-lining.

Can I reline a drain under a building?

Yes — this is one of the strongest arguments for no-dig methods. Relining a drain running under a house slab avoids the disruption and cost of breaking out concrete. The CCTV access is from manholes at each end. All major CIPP contractors have handled this scenario many times. Confirm access point dimensions before instructing — the liner drum and UV light train need to enter the pipe, which may require careful manhole access.

Does the Water Company need to be involved?

If the defective section is on your private drain (upstream of the public sewer boundary), you do not need water company involvement. If the defect is in the public sewer, contact your water company (e.g., Thames Water, Severn Trent) — they are responsible for the repair at no cost to you. For shared private sewers, agreement of all users is needed before proceeding.

Regulations & Standards

• BS EN 13566-4:2021 — Plastics piping systems for renovation of drains and sewers. Lining with cured-in-place pipes

• BS EN 13566-3 — lining with close-fit pipes (different technology)

• WRc Sewerage Rehabilitation Manual (SRM) — industry guidance for water company rehabilitation work

• Approved Document H — Building Regulations for drainage design and performance

• MCPF (Main Contractor Pre-Qualification Framework) — qualification for water company framework contractors

• CIPP Explained — CIPHE Technical Guidance — Chartered Institute of Plumbing and Heating Engineering

• WRc — Sewer Rehabilitation Research — technical research and standards

• NADC — No-Dig Drain Repair Guidance — National Association of Drainage Contractors

• BBA Certification for Drain Liners — product certifications for CIPP materials

• drain cctv survey — survey and MSCC4 reporting before specifying no-dig repair

• root intrusion — root intrusion treatment including relining options

• blocked drains — clearing before lining

• underground drainage — new drain installation standards