Soakaway Installation & Repair in Birmingham

Signs Your Soakaway Has Failed

A functioning soakaway clears surface water within a few hours of rainfall stopping. If yours is showing any of these symptoms, it may have silted up or may never have been correctly sized for the catchment area it serves:

• Garden waterlogged for days after rainfall — not hours. Normal ground saturation clears within a day or two; a failed soakaway stays wet for much longer.
• Standing water near the soakaway inspection point or above where the soakaway pit is located, indicating the void has silted or collapsed and water has nowhere to go.
• Surface water migrating away from the property — flowing across a neighbour's land or out onto the pavement — because the soakaway is not accepting it.
• Overflow drain running continuously or discharging to a watercourse or road drain even in moderate rainfall, showing the soakaway has insufficient remaining capacity.

Why Soakaways Fail

Most soakaway failures in Birmingham come down to one of three causes:

• Silting over time. Fine particles in surface runoff pass through old rubble-filled soakaways and gradually clog the voids. Without a geotextile wrap or upstream catch pit, even a well-installed soakaway will lose capacity over ten to fifteen years.
• Original undersizing. Many soakaways in older properties were installed without formal percolation testing or drainage calculations. An undersized soakaway works adequately in light rain and fails in heavier rainfall — the type that West Midlands gets increasingly often.
• Unsuitable soil conditions. Clay-heavy geology underlies a substantial part of Birmingham — particularly in the south and east of the city. Clay retains water rather than dispersing it, and a soakaway installed in clay without proper assessment simply doesn't work. This is probably the single most common reason we're called to a soakaway problem that turns out never to have functioned correctly in the first place.

What We Do

1. Percolation test. Before recommending a soakaway, we carry out a percolation test to measure how quickly water drains from your soil (expressed as the Vp value in mm/hour). This determines whether a soakaway is viable and, if so, how large it needs to be.
2. Design to BRE Digest 365 / BS EN 752. Where the test confirms a soakaway is suitable, we calculate the required volume based on the test result, the catchment area, and the design storm — not a rough guess at what looks about right.
3. Installation. We install modular plastic crate soakaways (preferred over rubble fill for their consistent void ratio and longevity), wrapped in geotextile to prevent silt ingress, with a catch pit upstream to intercept suspended particles before they reach the soakaway.
4. Connect to surface-water drain. The soakaway is connected to the existing surface water drainage from the property — downpipes, patio drains, driveway channels — and an inspection chamber is installed for future maintenance access.

When a Soakaway Is Not Viable

We will tell you clearly if a soakaway will not work on your plot. If the percolation test shows your soil drains too slowly — as is common in clay-heavy parts of Birmingham — we'll discuss the alternatives honestly:

• Attenuation tank — stores surface water and releases it slowly to an approved outlet (ditch, watercourse, or mains drain) at a controlled rate.
• Connection to the mains surface water sewer — subject to Severn Trent approval; an option where the public surface water sewer is nearby.
• French drain with outlet — for redirecting water away from a specific problem area rather than dispersing it into the ground.

For drainage issues related to an outside area, see also our outside drain unblocking service and our domestic drainage page for the full range of residential drainage work we carry out.

General drainage repairs — including surface water connections and pipe replacements — are covered on our drainage repairs page.