The short answer: there’s no single price, because no two sites need the same work. The cost of a percolation test depends mainly on:
- how many trial pits are needed
- which test (a BRE365 soakaway test, BS 6297 or both)
- the machinery and crew the site calls for
- access
- how many days the testing takes
- whether there’s water on site
- how far the site is from us
Below is how each one affects the price, so you can judge whether a quote is fair.
What actually drives the price
- How many trial pits the design needs. This is the biggest single factor. A small extension may need one or two; a larger site, or a scheme with several soakaways, will need more. Each pit has to be dug, then filled and timed three times over.
- Which test, or both. Surface water testing to BRE 365 and foul testing to BS 6297 are separate tests with separate results. Rural sites with no mains foul connection often need both. Doing them on one visit is far cheaper than two separate visits.
- The machinery the site needs. Most sites need a tracked mini digger to open the pits at the right depth. Deeper soakaway designs, hard ground or larger sites may need a bigger machine. We own our own machinery rather than hiring it in, which keeps this cost down.
- Access. If a machine can get to the test location, the work is straightforward. If it can’t (a walled back garden, a steep plot, no gate wide enough), the pits may have to be dug by hand, which takes considerably longer and more manpower.
- Manpower. A standard test is a two-person job. Hand digging, difficult access or a large number of pits can need a bigger crew.
- Number of days on site. Most tests are completed in a single day, but the three timed fills in each pit can’t be rushed. Slow-draining ground, a lot of pits, or both tests on one site can take the work into a second day or longer. Our proposals are priced for a day’s testing, with any additional day agreed with you in writing on site. We’ll tell you up front if we think more than one day is likely.
- Water supply. Each pit is filled three times, and a BRE 365 test uses a lot of water. If there’s no mains supply or tap close by, we bring a water bowser, which adds to the cost. A usable supply on site makes a real difference.
- Distance. Travel is built into every quote. A site twenty minutes from our Wolverhampton base costs less to attend than one three hours away.
Why quotes vary so much
If you gather three quotes you’ll often see a wide spread, and the cheapest isn’t always doing the same job. The most common reason for a low price is a test that cuts corners: a single trial pit where the design needs several, or one filling instead of three.
BRE Digest 365 asks for each pit to be filled and timed on three separate occasions, and the slowest result is used for the calculation. A single filling is quicker and cheaper, and it’s the sort of thing that gets picked up when the drainage design is reviewed. A retest costs more than getting it right first time.
Questions worth asking before you accept a quote
- How many trial pits is that price for?
- Does it include three timed fills per pit, as BRE 365 requires?
- Is a written report included, with the recorded times, or just a single figure?
- Does the price cover surface water only, or foul as well?
- Is water, machinery and travel included, or are they extras?
- Is the price for one day on site, and what does an extra day cost if the ground drains slowly?
- What happens if the ground fails? Is there a charge for a report that says infiltration isn’t viable?
That last one matters more than people expect. A failed test isn’t a wasted test: it’s the evidence your engineer needs to justify a different drainage approach, and it’s what a water company will want to see before accepting a surface water connection to the sewer. It should still come with a proper report.
How to get an accurate price quickly
We quote per site rather than from a price list, because the honest number depends on the factors above. The more we know up front, the sooner and more accurately we can price it:
- Know where the pits need to go? Use our detailed quote request to mark each pit on a map, with the pit sizes, access and water details. It’s the quickest route to a fee proposal.
- Not sure yet? Send us the postcode and roughly what’s proposed (extension, self-build, barn conversion or a full development), and we’ll advise which test you need.
Allow up to 48 hours for a fee proposal. The quote is free, and if we think you need a different test from the one you asked for, we’ll tell you before you commit.
or call us on 01902 475653.