Attenuation tank installer in Hampshire

Why the south of the county runs on storage

The coastal plain around Southampton, Eastleigh, Fareham and Portsmouth sits on clays, silts and a lot of made ground. Percolation results there are often too slow for a soakaway to empty between storms, so the water is sent on to a watercourse or sewer instead, at a rate the receiving network can take.

Under the 2025 national SuDS standards, infiltration sits near the top of the runoff hierarchy, so your engineer has to show the ground can't take the water before moving down to a controlled discharge. Once they have, the gap between what falls on the site and what the outfall is allowed to release needs somewhere to wait. That is the attenuation tank.

Chalk sites that still need a tank

The chalk downland through the middle and north of Hampshire usually drains well, but a good percolation result doesn't settle every job. Clay-with-flints can cap the chalk at shallow depth, and much of the chalk feeds the groundwater that supplies drinking water and the Test and Itchen. On some sites the engineer will keep runoff from car parks and service yards out of the ground and store it instead.

Where that happens the tank is fully lined, and the membrane joints decide whether it holds. Every one of ours is heat-welded, never taped.

How we work on Hampshire sites

We can supply the crates and membrane and fit them, or fit materials already delivered to your site. Sizing the tank and setting the flow control is your engineer's job; opening, forming and backfilling the excavation is your groundworker's. We don't dig. Crews travel from our Tamworth base and are sequenced into your groundworks programme.

Urban plots in Southampton and Portsmouth are often tight, with the tank going in beside live services, boundary walls or an existing building. We plan the membrane layout and the order of the crate build around the space the dig leaves us, and raise anything that would stop the tank matching the drawing before we start.

• Formation checked before we start, and you're told straight if it isn't ready
• 300gsm protective fleece, then an impermeable membrane cut to the tank geometry
• Each crate course laid level, up to the drawn volume and the specified loading class
• Pipe connections and the flow control made to match the drainage drawing
• A recorded test weld, plus the QA and handover file building control will ask for

Built the same at any size

Plenty of Hampshire tanks are small, under a single commercial unit or an infill plot. They get the same fleece, the same membrane welded panel to panel, the same connections tied into the scheme and the same recorded test weld before backfill as our largest, because a building inspector or adopting authority checks for those things whatever the volume.