ETA Range

Sizing is based on population equivalent (PE) — the number of people the system serves, not just bedrooms. The ET A Range typically covers small domestic installations from around 4PE up to larger multi-occupancy sizes, so as a rule of thumb count all regular occupants and add a margin for guests. If you're between sizes, it's always better to go up a size than risk an undersized system struggling with peak flows.

If the treated effluent discharges to a watercourse or to ground via a soakaway, you'll usually need to register or apply for a permit with the Environment Agency (or SEPA/NRW in Scotland and Wales). Discharges to a watercourse generally need a permit, while soakaway discharges below a certain daily volume may only need registration — check current thresholds before you install. Your installer or groundworker should factor this into the site plan from the outset, as it affects where the tank can legally be sited.

Yes — these tanks are commonly specified for new-build off-mains drainage as well as replacing failing septic tanks or older treatment plants. On replacement jobs, check the existing invert levels and pipe positions match up, as retrofitting can sometimes need extra fall or a pumped outlet if the new unit sits differently to the old one. A site survey before ordering avoids costly surprises during installation.

Like all sewage treatment plants, it needs periodic desludging (typically annually, though this depends on usage) and a service check to keep the mechanical or aeration components working correctly. Most units come with manufacturer guidance on service intervals, and keeping records is worth doing for building control and resale purposes. Neglecting maintenance is the most common cause of poor effluent quality and permit breaches.

Installation involves excavating to the correct depth, providing a suitable pea-shingle or concrete surround depending on ground conditions and water table, and getting the inlet/outlet inverts and fall right for gravity flow. Tanks must be installed level and correctly backfilled to avoid distortion, particularly with GRP or plastic constructions. We'd always recommend using a groundworker experienced with sewage treatment plant installations rather than treating it as a standard drainage job.

The range is built from durable GRP (fibreglass) or polyethylene construction, both of which are lightweight for delivery and installation but need proper backfill support once in the ground — they're not designed to bear structural loads unsupported. Avoid siting under driveways or parking areas unless the tank and installation are specifically rated for it, and always keep appropriate access clearance for future desludging and servicing.