Patch repair, pipe lining or excavation: which drain repair do you need?

There are three realistic ways to repair a damaged drain: a localised patch liner, a full cured-in-place liner along the run, or excavation and replacement of the pipe. They differ enormously in cost and disruption, and which one you need is determined by what the defect actually is, where it sits and whether the pipe still holds its shape.

That means the decision cannot be made from the surface. Any contractor quoting to dig without having put a camera down the run first is guessing, and guessing always defaults to the most expensive option. A CCTV survey with a written report and a located defect is the document that decides the method.

A patch liner is a resin-impregnated sleeve positioned over a specific defect using a packer, inflated against the pipe wall and left to cure in place. When the packer is withdrawn, a rigid section of new pipe wall remains bonded over the damage.

It suits single, well-defined defects: one cracked or fractured section, a displaced joint, a hole where roots have entered, an open joint letting soil in. It is installed through an existing chamber with no excavation, and most patches are completed within a few hours.

It is the cheapest repair by a distance — typically a few hundred pounds against thousands for a dig — and the least disruptive. Its limitation is that it only fixes what it covers. If a run has multiple defects spread along its length, patching each one individually stops making sense.

A full liner works on the same principle applied along a whole length of pipe. A resin-saturated liner is inverted or winched into the run between chambers and cured, forming a continuous new pipe inside the old one.

It suits runs with several defects, general deterioration in ageing clay, or persistent root ingress at multiple joints — because a liner seals every joint at once, it removes the route roots use to get in. A properly installed liner has a design life comparable to a new pipe.

It costs more than a patch and far less than excavating the same length, and it is still a no-dig operation from existing access points. The main constraints are that the pipe must be structurally intact enough to take the liner, the run needs suitable access at each end, and the liner slightly reduces the internal diameter — rarely a practical issue on a domestic run, but relevant on a system already running at capacity.

Excavation means opening the ground, removing the damaged section and laying new pipe. It is the only option when the pipe has lost its shape: sections that have collapsed inwards, been crushed under vehicle loading, or dropped out of alignment so far that a liner cannot be drawn through.

It is also the answer to problems a liner cannot solve, such as a run laid with insufficient fall so that water stands in it, or a length that has to be rerouted around an obstruction or a new structure.

The cost sits well above the other two methods, and the reinstatement is often the larger part of it. Relaying pipe under a lawn is one thing; taking up and replacing a block-paved driveway, a patio or a concrete slab is another, and the surface reinstatement can exceed the drainage work itself.

On cost, patch is lowest, full lining is mid-range and excavation is highest — usually by a multiple rather than a margin. On disruption, patch and lining involve no excavation at all and typically finish within a day; excavation means open ground, spoil, plant access and reinstatement.

On durability, a correctly installed patch or liner is a permanent structural repair, not a temporary measure. That is worth stating plainly because the assumption that no-dig means short-term still puts people off the cheaper option unnecessarily.

On applicability, patch fixes one defect, lining fixes a length, and excavation fixes anything — including the cases the other two cannot touch. The correct approach is to work up from the least invasive method that will genuinely solve the problem, rather than down from the most invasive.

Insist on a CCTV survey with footage and a written report before any repair is priced. Ask for the defect to be located from the surface with a sonde, and ask which side of your boundary it sits on — if it is on a shared or public length, the sewerage undertaker may be responsible for the repair entirely.

Ask specifically whether a patch or a liner was considered and why it was ruled out if excavation is being proposed. A firm that only offers excavation may not have lining capability, which is a reason for their recommendation but not a reason for your decision.

If you are claiming on insurance, the survey report, footage and location reference are what the insurer will ask for, so get them at the diagnosis stage rather than after the work is done.