Drainage, Treatment Plants and Septic Tanks
If a site isn't on mains drainage, this is usually the thing that decides whether it can be built at all — and it's the element most likely to hold up a planning application or a building control sign-off.
We design and install foul drainage, sewage treatment plants, septic tanks and pump stations across Surrey and Hampshire, and we can advise at design stage as well as install. It's almost always cheaper to get the drainage strategy right before the drawings are finalised than to work around it afterwards.
Sewage Treatment Plants
For properties off the mains, a packaged treatment plant is now the default. It treats the effluent to a standard clean enough to discharge to a drainage field or, with permission, to a watercourse.
Since the General Binding Rules came into force, a septic tank discharging directly to a stream, ditch or river is no longer permitted. If you have one, it has to be replaced or upgraded — usually to a treatment plant — or connected to the mains. It's the kind of thing that surfaces during a house sale, at the worst possible moment.
We'll size the plant to the property, install it, connect it, and leave you with the paperwork you need.
Septic Tanks and Drainage Fields
Where a septic tank is still the right answer, it discharges to a drainage field rather than a watercourse. The field has to be sized against a percolation test — dig a hole, fill it with water, time how fast it drains — and the results dictate the length of the run.
We carry out percolation testing and design the field around the result, allowing for the setback distances from buildings, boundaries, watercourses and any borehole or well.
Septic Tanks and Drainage Fields
Where a septic tank is still the right answer, it discharges to a drainage field rather than a watercourse. The field has to be sized against a percolation test — dig a hole, fill it with water, time how fast it drains — and the results dictate the length of the run.
We carry out percolation testing and design the field around the result, allowing for the setback distances from buildings, boundaries, watercourses and any borehole or well.
Pump Stations
Not every site falls the right way. Where the drainage run can't reach the sewer or the treatment plant under gravity, a packaged pump station lifts it. We install and connect these, size the chamber and pumps for the flow, and set them up so they can actually be maintained — which means access, not a chamber buried under a new patio.
Surface Water, Soakaways and Rainwater Harvesting
Foul is only half the job. Surface water has to go somewhere too, and on most sites now that means a soakaway rather than the sewer.
We're also installing a growing number of rainwater harvesting tanks, which take roof water into an underground tank for use on the garden or, with the right treatment, in the house. On a big roof with a big garden the numbers stack up, and it takes load off the soakaway at the same time.
Oil and Gas Tanks
We install underground and above-ground oil tanks and LPG tanks, with the bases, bunding and excavation that go with them.
Common Questions About Drainage and Treatment Plants
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Not illegal, but it will hold up the sale. Under the General Binding Rules, a septic tank discharging directly to a stream, ditch or watercourse must be replaced, upgraded or connected to the mains — and if the property is being sold, that has to be dealt with before completion. It's the most common reason we get called out at short notice: the buyer's solicitor raises it and suddenly there's a deadline.
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For most domestic installations you register under the General Binding Rules with the Environment Agency rather than applying for a permit, provided you meet the conditions on volume, discharge point and distance from watercourses and boreholes. If you can't meet them — usually because of where the discharge has to go — you'll need a permit. Building regulations approval applies either way. We'll tell you which route your site is on before you commit to anything.
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The plant itself is usually the smaller half. A domestic unit for a typical house runs to a few thousand pounds; the excavation, base, backfill, pipework, electrical connection and commissioning is generally the larger share. Total installed costs across the industry commonly fall in the region of £8,000 to £15,000, and go higher where there's high groundwater, rock, or difficult access for machinery.
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A properly installed and serviced plant should give you twenty to thirty years or more, though pumps and blowers are consumables and will need replacing well before then. Most failures we're called to aren't the plant — they're the installation. A unit set on inadequate backfill, or a chamber that was never accessible for servicing, will cause trouble regardless of the brand.
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Usually, but the discharge is the question rather than the plant. Clay drains slowly, which means a percolation test may rule out a drainage field or dictate a very long one. Where that happens the answer is normally a treatment plant discharging to a watercourse with the right consent. We carry out the percolation testing and will tell you what your ground will actually take.
Get a Price
Send over the drawings, or if you're at an earlier stage than that, tell us where the site is and what you're hoping to build. We'll tell you what the drainage is likely to involve before you've spent money on a scheme that can't be drained.
We work across Surrey and Hampshire, and often as part of a full groundworks and foundations package. Get in touch or call Dan on 07808 781794.