Patch Lining or Full Relining: Which Do You Need?

What a patch liner is

A patch is a short section of resin impregnated liner, usually between half a metre and a metre and a half long, positioned over one specific defect and cured in place. It bonds to the host pipe either side of the fault and forms a seal across it. The rest of the run is left exactly as it was.

Patches are ideal for a single fractured length, one open joint, or one point of root ingress in an otherwise sound pipe. They are quick, often completed in a few hours, and they are the cheapest structural repair available.

What a full length liner is

A full liner runs from one chamber to the next, rebuilding every metre of the run in one continuous piece with no joints for roots to enter. Branch connections are reinstated afterwards. It costs several times what a single patch costs but it removes every joint in the run rather than one.

The absence of joints is the key point. Most defects in old clay drainage occur at joints, so a run with three failing joints has, in practice, a whole line of joints of the same age and condition, and the two that are currently sound are simply behind the others.

The decision in practice

• One defect, rest of the run clean and sound: patch.
• Two defects close together: single longer patch spanning both.
• Three or more defects along one run: full liner, almost always cheaper over five years.
• Root ingress at multiple joints: full liner, because roots will simply find the next joint.
• Any defect in a run also holding standing water: neither, excavate and relay that section.
• Collapse or severe deformation: excavation for that section, with lining either side if useful.

When a patch is a false economy

Where a run is generally worn, a patch treats the symptom that showed up first. Roots that are cut back and sealed at one joint will find the next joint within a season or two, and you pay a call out, a survey and a repair each time. Three patches on one run typically cost more than the full liner would have.

It is also a false economy where access is hard won. If getting equipment to the chamber involves lifting slabs or moving a lot of material, doing that once for a full liner is better than doing it three times for patches.

When a full liner is over specification

A single fracture in a plastic run laid twenty years ago is exactly what a patch is for. The rest of the pipe is not near the end of its life, the joints are sealed rings rather than mortar, and there is no reason to rebuild forty metres of sound pipe.

The same applies where one specific event caused the damage, such as a fracture directly under a new driveway crossing. Fix the damage, not the pipe.

How we quote it

We survey first and price from the footage, showing you the defects and their distances so you can see the reasoning rather than take our word for it. Where a run sits close to the boundary between the two options, we will quote both and explain the five year view rather than just the cheapest number today.

We carry out patches, full liners and excavation with our own teams across West Lothian, Edinburgh, Falkirk, Lanarkshire and Fife, so the recommendation is not shaped by what we can subcontract.

Thinking about it over five years

The honest way to compare the two is not what each costs today but what the run will have cost by the time it stops causing trouble. A patch on a genuinely isolated defect is finished business. A patch on the first of several failing joints is the first of several invoices, plus the call outs and surveys in between.

We set that out plainly when we quote, with the footage on screen, so the choice is made from what the pipe actually looks like. Where the answer really is a single patch, that is what we recommend, because a run of old clay in good order does not need rebuilding.

Questions we get asked