Case Study: Soakaway Replacement in Verwood, Dorset
Updated: Oct 4
The call came in last February, after a fortnight of the kind of rain east Dorset has been getting more of every winter. A family in Verwood had watched their back lawn turn into a shallow pond for the third year running. This time the water was sitting against the patio doors, and they'd had enough.
A few details are changed here for privacy, but the job is real and the pattern is one we run into constantly around Verwood, Ferndown and Ringwood. If your garden behaves the same way, the diagnosis below will probably sound familiar.
The symptoms weren't the actual problem
Water was still lying on the lawn three days after the rain stopped. The gully by the back door gurgled and backed up whenever the roof was shedding properly, and there was a dark tide mark on the render where the splash-back had been going on for years. The owners had already had the gutters cleared and the drain rodded by someone else. Neither made any difference, which told us the problem wasn't sitting in the pipe run at all.
Houses of that era around Verwood were routinely built with a rubble-filled soakaway pit for rainwater. A hole, some brick hardcore, and a bit of optimism. Fifty years of silt washes in, the voids between the rubble close up, and the pit stops soaking away. It just fills, and then the pipe backs up behind it.
What the CCTV survey found
We put a camera through 26 metres of surface water run before quoting anything. We always survey first, because guessing at drainage is how people end up paying for the same job twice.
Three things showed up. The pipe had almost no fall across the last 8 metres, closer to 1 in 150 than the 1 in 80 you want, so silt had been settling out for years. Fine roots from a leylandii hedge had found a cracked joint about 9 metres out. And the old pit was completely blind: water went in, the camera showed it standing there, nothing was going anywhere. The full survey, with written report and footage, came to £260.
Why we test the ground before we price a soakaway
Verwood sits on the Poole Formation, which is mostly sand and gravel and usually drains well. Usually. There are clay bands running through it, and we've had two gardens a couple of hundred yards apart where one took water away in minutes and the other held it like a bucket. You can't price a soakaway off a postcode.
So we ran a percolation test to BRE Digest 365: three trial pits, each filled and timed three times, to get a real infiltration rate. That figure sets the crate volume. Building control will want to see it too if the work is notifiable. Budget £400 to £600 for a properly reported test. Part H also wants a soakaway at least 5 metres away from the building, which ruled out the obvious spot near the patio.
The rebuild, start to finish
Dug out and removed the old rubble pit, 3.4 tonnes of silted hardcore carted off site.
Installed a 3.2 cubic metre modular crate soakaway 6.5 metres off the rear wall, wrapped in geotextile with a gravel surround, sized off the percolation result.
Re-laid 14 metres of 110mm surface water pipe at a proper 1 in 80 fall and cut out the root-damaged section.
Added a catchpit with a silt trap ahead of the soakaway, so it can be jetted out in future instead of dug up again.
Ran an 18 metre land drain along the low side of the lawn into the same system, then reinstated the turf.
Five days on site with two of our groundworkers and a mini digger, plus the test day a fortnight earlier. The lawn looked rough for a season, which we'd warned them about. It had knitted back together by June.
What the job cost
These are our own September 2026 rates for this part of Dorset, inclusive of our margin. They're what a customer would actually pay us, not trade-only figures or a national average:
CCTV survey with written report: £260
BRE 365 percolation test, three pits: £400 to £600
New 3.2m³ crate soakaway, excavation and muckaway included: £2,650 to £3,850
Land drain: £70 to £100 per metre laid
Catchpit, new gully and 14 metres of re-laid pipe: £520 to £620
All in, this one landed between £5,400 and £7,600, depending mainly on how much spoil had to leave site. The variables that move that number most are digger access down the side of the house, how deep we go before we hit free-draining ground, and whether the water table is high, which it often is closer to the Moors River.
Related reading
Water sitting in your garden this autumn?
Autumn is when this gets noticed, and it's the sensible time to sort it before winter rain starts working on your foundations and patio. We handle drainage and civil works across Verwood, Ferndown, Ringwood, Wimborne and the rest of east Dorset, and we survey every job before we put a price on paper. Book a site visit with us and we'll tell you what your drains are actually doing.
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