Summary

Leak repair is the most frequent emergency-call plumbing job and one of the most commonly mis-quoted. The customer's mental model is "fix the leak" — a single line item. The trade reality is three jobs: find the leak (detection), repair the source (the cheap part), and reinstate the access damage (often the largest cost). Quoting these as one number is how leak repairs become disputes.

Detection complexity drives pricing more than the repair itself. A visible weep under a sink trap is 15 minutes' work. A pinhole in a copper pipe behind a plasterboard wall, dripping into a void, soaking into a downstairs ceiling, is potentially £1,500-£3,500 including detection, access cutting, repair, drying (3-5 days with industrial dehumidifiers), and full make-good (plaster, paint, sometimes flooring). Always price these scenarios as separate scopes.

This guide covers the full leak repair spectrum: visible joint repairs, concealed pipework, central heating leaks, underground supply leaks, and the increasingly common leak detection insurance work where the trade-off is paid by the insurer but specified by a loss adjuster. For boiler leaks see boiler no pressure; for cylinder leaks see hot water not working; for radiator leaks see radiator replacement pricing guide.

Key Facts

Quick Reference Table

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Leak Scenario Detection Required Repair Time Access Damage Total Range (Regional)
Visible joint under sink No 0.25-0.5 hr None £85-£180
Toilet base leak No 0.5-1 hr None £120-£260
Behind bath panel Partial 1-2 hr Panel re-fit £180-£380
Behind kitchen unit Partial 1-2 hr Unit re-fit £220-£450
Concealed wall pipe (plasterboard) Possibly 2-4 hr Wall cut + plaster + paint £380-£900
Under floorboards (visible) No 1-3 hr Board lift + relay £280-£650
Under solid floor / screed Yes 2-6 hr Screed + tiles £950-£3,200
Underground supply (cold mains) Yes 2-4 hr Excavation + reinstate £750-£2,800
Insurance-managed full repair Yes (logged) Variable Full make-good £1,800-£8,500+

Detailed Guidance

Visible leak repairs — the bread and butter

Visible leaks are the simplest jobs: a dripping compression joint, a failed push-fit, a corroded radiator valve, a worn tap washer. Pricing is call-out + 0.5-1 hour + parts. Always charge the call-out as a separate line — the customer expects this and it covers the travel and assessment. The repair itself is rarely the cost driver; the cost driver is being there.

Common visible leak categories and pricing:

The pricing trap is the "while-you're-here". The customer often points out three more weeps after you fix the first. Always re-quote for each — never lump them in to be friendly. Trade convention is that the first call-out covers one fault; each additional fault is at hourly rate plus parts.

Concealed pipework — detection then repair

Concealed leaks fall into two categories: (1) suspected from secondary evidence (damp patch on a ceiling, smell, pressure drop) and (2) confirmed from a visible source on inspection. Detection methods scale by cost: visual inspection (free, included in call-out), moisture meter (£40-£80 detection charge), borescope inspection of voids (£80-£180), acoustic leak detection (£150-£300), thermal imaging (£200-£400), tracer gas (£350-£650), and full insurance-led investigation (£450-£1,200).

The diagnostic decision tree:

Leak symptom (damp / pressure drop)
  │
  ├─ Localised damp patch?
  │    ├─ Yes → moisture meter + borescope first
  │    └─ No → acoustic / thermal imaging
  │
  ├─ Central heating losing pressure?
  │    ├─ Daily drop → pressure test, pinhole likely
  │    ├─ Weekly drop → PRV / expansion vessel suspect
  │    └─ Monthly drop → normal for old systems
  │
  └─ Cold mains pressure normal?
       ├─ Yes → likely cylinder / DHW circuit
       └─ No → underground supply leak suspect

Once located, the repair is one of: cut and remake the joint, replace a section of pipe (10-cm coupling, hot tap drainage), or fit a leak-clamp (temporary, BS 1306). Always cut back to clean copper or new plastic and re-make in the same material. Mixing copper and plastic with push-fit transitions is allowed but never mid-wall — keep transitions accessible.

Central heating leaks — special considerations

Central heating systems are pressurised (1-2 bar typically), continuously hot (50-80°C), and contain inhibitor chemicals. Leaks in CH systems present differently to cold water leaks: lower-volume continuous weep, often manifesting as inhibitor staining on a ceiling or a brown patch on a wall.

Pricing differences: (1) the system needs draining or freezing (pipe freezer kit £80-£180 hire) before joint work, adding 30-60 minutes; (2) inhibitor must be replenished after repair (£15-£35 inhibitor + 30 mins refill); (3) corrosion is the typical root cause, not a single joint failure — the leak indicates pipe wall thinning, and the customer should be advised that adjacent pipework may follow within 12-24 months; (4) where multiple joints fail in quick succession, consider a power flush (£350-£550, see power flush pricing guide) and inhibitor top-up.

Lockshield and TRV body leaks are typically £120-£280 visit cost. Pinhole leaks in solid-floor copper pipework are the highest-cost CH leak scenario: lifting tile or screed, cutting and re-routing in plastic, and reinstating the floor — frequently £950-£2,500.

Underground supply leaks

Cold water service pipes (mains supply from boundary stopcock to internal stop tap) are the silent expense. They typically run under driveways, paths, and lawns; failures are usually pinholes in lead or galvanised iron (pre-1985 stock) or root-damage to MDPE (post-1985 stock).

Detection requires either acoustic correlation (£250-£450) or tracer gas injection (£350-£650). Repair is rarely a patch — best practice on lead supplies is full replacement with 25mm MDPE blue from the boundary stopcock to the internal stop tap. Mole-plough or open-trench installation:

Always involve the local water authority — most have a free repair scheme on supply pipes from the boundary stopcock into the property (subject to terms) and offer a free MDPE replacement under "leakage allowance" schemes. Quoting before checking is a missed cost reduction.

Insurance-led leak repair work

Insurance-paid leak detection and repair is a fast-growing trade segment. Loss adjusters specify the work; the trade invoices the insurer or the homeowner (who claims back). Pricing is rate-card based — typically £75-£110/hr labour, £150-£400 detection, plus materials and make-good as separate line items.

Insurance work requires evidence: dated photographs of the leak source before repair, the failed component retained, written cause-of-loss statement. The make-good is typically scoped by the loss adjuster's surveyor (separate scope) and may be subbed to a different trade — the plumber repairs the leak only.

Trade margins on insurance work are tighter than direct private work but volumes are higher and payment is generally reliable. Be careful of "Approved Repairer" schemes that lock you to insurer rate cards — they suit specialist leak-detection contractors but underprice general plumbers.

Frequently Asked Questions

How much should a leak detection cost on its own?

Standalone leak detection (without repair) typically prices at £150-£400 for a residential visit, depending on the method needed. Visual + moisture meter is the cheapest (£80-£150); acoustic correlation is mid-range (£200-£300); thermal imaging is £250-£400; tracer gas is £350-£650. Insurance-led full investigations with written reports are £450-£1,200. Detection-only visits do not include any repair — that is quoted separately after the leak is found.

Should I quote a fixed price or hourly rate for leak repairs?

Mixed. Quote a fixed call-out fee plus an hourly rate for the first hour or two, with a written-on-site re-quote if additional work is needed beyond that. Pure hourly rates feel open-ended to customers and create disputes. Pure fixed pricing fails when the leak turns out to be hidden — you absorb the cost of the surprise. Fixed call-out + hourly thereafter balances risk fairly.

Who pays for access damage and reinstatement?

In a private job, the customer pays — but they must be told upfront. The quote should separate "leak repair" from "access reinstatement" and the customer signs off both before work starts. In an insurance claim, the insurer pays for both the repair and the reinstatement provided the cause-of-loss falls within the policy (sudden and accidental damage typically covered; gradual deterioration sometimes not). Always advise customers to notify their insurer before authorising significant make-good work.

Can I use a leak sealant additive instead of finding the leak?

Sometimes — but document the trade-off. Sealant additives (e.g. Sentinel Leak Sealer X100, Fernox F4) work for very small pinhole leaks in sealed central heating systems where the leak is inaccessible and the financial cost of finding and repairing it is disproportionate. They are NOT suitable for visible leaks, structural leaks, or potable water systems. Always inform the customer in writing that sealant is a temporary measure (typical service life 2-5 years) and that the underlying pipework should be replaced when access becomes possible.

What if the leak is in a soil/waste pipe rather than a water supply pipe?

Soil and waste leaks are typically cheaper to find (smell, staining usually localised) but more expensive to repair due to the larger pipe diameter and the need to drain/isolate during repair. A cracked plastic soil pipe joint repair is £140-£320; a cast-iron waste section replacement (1970s housing) is £450-£950 because cast iron requires specialist couplings (e.g. flexible couplings or Mission no-hub clamps) and the cutting is slower with a chain pipe-cutter or angle grinder.

Regulations & Standards