Septic Tank Problems South Cerney | What to Do

If your garden smells like a farmyard and your toilets are sluggish, you're probably already aware that something's wrong with your off-mains drainage. What you might not know is whether it's the tank, the soakaway, or both. And if you haven't looked at the rules that came in during 2020, there's a reasonable chance your system is now technically non-compliant without anyone having told you.

South Cerney, Coates, Kemble, Sapperton, Down Ampney, and dozens of other villages around the Cirencester GL7 area sit well outside the mains sewer network. That means septic tanks and soakaways aren't a quirky feature. They're the entire drainage system for tens of thousands of homes and businesses.

What a septic tank actually does (and where it goes wrong)

A septic tank separates solids from liquid. Solids sink to the bottom and break down anaerobically. Liquid, the effluent, flows out of the tank and soaks into the ground through a soakaway or drainage field. Simple in theory. A lot can go wrong in practice.

The three most common failures:

• The tank hasn't been emptied regularly. Sludge builds up until it starts pushing into the soakaway. Once solids enter the drainage field, the damage is largely done.
• The soakaway is clogged or saturated. The ground around South Cerney can be poorly draining in wet winters. If the soil can't absorb effluent fast enough, it backs up or breaks surface.
• The inlet or outlet baffles have failed. These are plastic or concrete fittings inside the tank. When they corrode or break, flow patterns go wrong and solids escape.

The symptom you're most likely to notice first is a wet, smelly patch of ground above the soakaway. Or slow drains throughout the house. Or, on a bad day, sewage backing up into a ground-floor toilet.

The 2020 general binding rules. What changed and why it matters

In January 2020, the Environment Agency's general binding rules for small sewage discharges became legally binding. If you have a septic tank in England that discharges directly to a watercourse, a ditch, or a stream, that's now illegal. Full stop.

South Cerney has water everywhere. The Cotswold Water Park is on its doorstep, the Churn runs nearby, and the whole area is threaded with drainage ditches. If your septic tank was installed before 2020 and it discharges to a ditch rather than a soakaway in the ground, you're in breach of the rules and you'll need to either:

• Install a drainage field (soakaway) that meets BS 6297, or
• Upgrade to a sewage treatment plant, which does produce a cleaner effluent and can legally discharge to a watercourse under a separate permit.

This isn't theoretical. The Environment Agency does investigate complaints, particularly around the Water Park. A neighbour, a dog walker, or a local fisherman noticing discolouration in a ditch is enough to trigger an inspection. The fine for a serious breach can run to tens of thousands of pounds.

If you're not sure what your system does, a CCTV drain survey can trace where the discharge goes. That's something we do regularly around the GL7 villages.

Soakaway failure: what's actually happening underground

A soakaway isn't a hole full of rubble. A proper drainage field is a network of perforated pipes laid in gravel trenches, sized according to a percolation test carried out when the site was assessed. When it's working, effluent trickles slowly into the surrounding soil and microbes in the ground treat it.

When it fails, it's usually because:

Biomat has built up. A greasy, anaerobic layer of bacteria coats the walls of the trenches and blocks the pores in the soil. This happens when solids have reached the soakaway, or when the tank was never emptied and the soakaway has been overloaded for years.

The system is undersized. Planning rules on soakaway sizing have changed over the decades. A drainage field installed in 1985 for a three-bedroom bungalow may never have been adequate for a property that now has four bathrooms and a dishwasher.

Tree roots have invaded. Willows and poplars love effluent. If you have mature trees within 15 metres of the drainage field, root intrusion is worth checking.

A failed soakaway can sometimes be rested and partially restored. Turn off the flow, give it six to eight weeks in dry weather, and some biomat does break down. Realistically though, a heavily clogged drainage field usually needs replacing. That means a new percolation test, a new design, and excavation.

Emptying: how often, and why people leave it too long

The standard advice is every twelve months. Most people stretch it to three or four years. Some systems can go two years without trouble if the household is small and the tank is generously sized. But there's no version of this where leaving it indefinitely works out.

When a tank gets pumped, a reputable emptier will check the baffles and flag obvious problems. That's your early warning system. If you're buying a property with a septic tank around South Cerney or Kemble, get the emptying records. No records is a bad sign. A CCTV survey of the tank and drainage field before exchange is money well spent.

Drain repairs and what carries a guarantee

If a CCTV survey reveals a cracked tank, collapsed inlet pipe, or a failed baffle, those are repairable. Pipe relining can fix a fractured outlet run without excavation. Drainsco's 20-year guarantee applies to remedial work of that kind, meaning drain repairs, relining, and pipe replacement. It doesn't cover blockage clearance, which is a one-off service.

A new drainage field is a civil engineering job. It needs a competent designer, a percolation test, and in most cases permitted development approval from the Cotswold District Council. We can advise, carry out the drainage investigation, and refer you to the right people for design and installation if that's the route you need to take.

When to pick up the phone

Sewage breaking surface is an emergency. Don't wait for a dry week. Call the same day.

Slow drains, a smell from outside, or a tank that's overdue for emptying? That's not an emergency but don't let it run into winter. Waterlogged ground in December makes soakaway problems dramatically worse and any excavation work more expensive.

Drainsco covers South Cerney, Cirencester, and the surrounding GL postcodes. Engineers are on call 24 hours a day, seven days a week. We'll give you a clear price before we start, and there's no call-out fee.