The equation has two terms and you are shown one
Rate multiplied by hours. Every comparison people make before booking is on the first term, because it is the one printed on a page. Every bill that shocks people afterwards was decided by the second.
A rate is cheap or dear; an afternoon is cheap or dear. The second range is wider, and it is the one nobody quotes.
The published rates, and what the first hour costs
Four London firms publish a leak detection price. Here is what each one produces at the point you have been in the property for one hour, calculated from their own published rates and minimums. The arithmetic is ours and the inputs are theirs.
| Firm | Published rate | First hour, as published or as calculated |
|---|
| Aspect | From £54.00 plus VAT per half hour, one-hour minimum | £108.00 plus VAT (our calculation from their rate and minimum) |
| Pimlico Plumbers | £165 excl. VAT per hour, 7am–6pm, one-hour minimum | £165 excl. VAT |
| 0800 Homefix | Trace and access from £950.00 plus VAT, described as a starting price | Not billed by the hour for this product |
| ADI Leak Detection | £595 plus VAT full day for pipework, £495 plus VAT half day for roof or structural | Not billed by the hour; a full day is allocated to every pipework investigation |
| Leak Fix London | £150 per hour | £150, and nothing at all if we do not find it |
Aspect's rate guide describes its figures as starting-from prices and says actual rates vary by postcode. Pimlico's card is dated 15 January 2026 and was read from an Internet Archive snapshot of 7 June 2026, because their site was behind bot protection. 0800 Homefix flag their figure as a starting price whose final cost depends on complexity. All checked 19 September 2026.
The three-hour problem
Take the lowest published half-hourly rate in that table and run a search that does not work. Three hours at £54.00 plus VAT per half hour is £324.00 plus VAT, and you still do not know where the water is going. Book again next week and the meter restarts at zero.
Now run the same three fruitless hours where the search time is not charged if it fails. The cost is nothing. Not discounted, not credited against a future visit. Nothing.
The rate you compare on a price list is the price of a good outcome. The price of a bad one is the number that actually varies between firms, and it is the one nobody advertises.
Three ways a low rate turns into a long bill
The rate is for a different product
0800 Homefix publishes general plumbing labour at £120.00 plus VAT for Monday to Friday, 07:00 to 18:00, and publishes trace and access separately at £950.00 plus VAT as a starting price. Those are two products on one rate card, and the firm is being entirely clear about it. The trap is not theirs: it is booking the cheaper line for a job that is actually the other one, anywhere in the market. If you ring for "a plumber, hourly" and the problem is a hidden leak, the hourly plumber will spend hours on it.
The increments and the minimum
Aspect's terms state that after the one-hour minimum, charges are made by the half hour rounded up to the next half hour. Pimlico's card states 15-minute increments after the first hour. 0800 Homefix publishes half-hour increments from the point of arrival. On a job that runs to two hours and ten minutes, those three structures bill two and a half hours, two and a quarter, and two and a half. The rate did not change and the invoice did.
The tail nobody quoted
Detection ends with a hole. The repair and the making good are separate work, and on a tiled screed floor the making good is often the largest of the three. ADI publishes that drying and reinstatement are separate work and that it can recommend a national company for it. That is honest and it is also a second and third supplier, each with their own mobilisation and minimum. The full comparison of who does what is in detection only, or detect and repair.
Where the higher structures genuinely win
This cuts against us as much as for us, so it goes in plainly.
- A fixed day rate wins on a hard leak. ADI's £595 plus VAT allocates a full day to a pipework investigation. If your leak is a cold feed under 60mm of screed in a period conversion with no record of the pipe run, a day is a realistic estimate of the work and the price risk sits with them, not you. On that job a fixed price is the cheaper outcome and the calmer afternoon.
- A half-hourly rate wins on an easy one. If a pressure test is going to settle it in forty minutes, buying half hours rather than days is straightforwardly better value.
- A national wins when availability is the constraint. Aspect publishes 24-hour, 365-day coverage on its leak detection page; Metro Rod and Dyno-Rod both publish round-the-clock availability. At 3am with water coming through a ceiling, the cheapest rate in London is worthless if nobody answers.
- Insurance-backed cover wins if you have been claiming repeatedly. HomeServe sells the problem as cover rather than as a job, with a stated excess per new problem and a 28-day initial waiting period during which new problems are not covered. For a household with recurring plumbing failures that arithmetic can work; for a one-off hidden leak today it does not, because of the waiting period and because pre-existing issues are not covered.
What actually keeps your bill down
- Do the meter test before you call. Everything off, read, wait an hour, read again. Free, and it converts a suspicion into a measurement that shortens every search.
- Write down the pattern. When the damp appears, what was running, how the boiler pressure behaves over a week. Pattern is what narrows a search, and narrowing is what costs money.
- Clear the access before anyone arrives. An hour moving furniture bills identically to an hour tracing.
- Arrange the neighbour in advance. Waiting in a hallway for access to the flat above is the most expensive part of many London flat jobs, on any rate card.
- Do not open anything speculatively. A floor already lifted in the wrong place destroys evidence and adds reinstatement.
- Ask what happens if it is not found. That single answer changes the expected cost more than any rate comparison in this article.
Our number, and its limits
£150 per hour, fixed before we attend, with no call-out fee, no out-of-hours uplift and no find, no fee on the search. It is not the lowest published rate in London and we are not going to argue that it is.
What it is, is a rate that cannot be revised once somebody has seen your floor, attached to a guarantee that prices the failures into the successes instead of billing them to whoever happened to have the hardest leak. It is still a rate and not a total, and the difference between those two is worked through in why leak detection is charged by the hour. If you want the published UK averages alongside it, they are in leak detection cost in London.
