HarlequinSewage Treatment Plants

Sizing is based on population, not property size — Harlequin plants are rated from 6 to 50 person equivalents. As a guide, count the maximum number of bedrooms plus two, though holiday lets, HMOs and commercial premises need a more careful assessment of actual usage. Our team can help you work out the correct model from your occupancy figures.

Yes, you'll need to notify or apply to the Environment Agency (or SEPA/NRW in Scotland and Wales) for a permit or exemption, depending on the discharge location and flow rate. You'll also need to comply with Building Regulations, particularly Part H, covering positioning, access and pipework. Discharges to a watercourse need tighter consent than those to ground via a soakaway.

Yes, upgrading from a septic tank to a Harlequin treatment plant is one of the most common installations we support, particularly where the General Binding Rules now prohibit septic tank discharge to a watercourse. The existing tank is usually removed or decommissioned, and the new plant is sited following a fresh drainage assessment. It's worth checking your soil percolation and outlet route before ordering, as this affects the final installation design.

Harlequin plants need an annual service by a competent engineer to check the air blower, mechanical components and effluent quality, plus periodic desludging — typically every 6 to 12 months depending on usage. Most models are fitted with an alarm to flag faults or high sludge levels early. Keeping up with servicing protects your warranty and keeps you compliant with your discharge permit conditions.

GRP (fibreglass) tanks are rigid, robust and well suited to sites with high water tables or unstable ground, as they resist flotation and ground movement well. Polyethylene tanks are lighter, easier to manoeuvre on tricky access sites, and generally more budget-friendly. Both are built to the same treatment standard, so the choice usually comes down to ground conditions and site access rather than performance.

Make sure the excavation is ready, with clear, level access for the delivery vehicle and any lifting equipment required, as these tanks are large and awkward to reposition once off the lorry. Confirm the inlet and outlet invert levels match your drainage design, and have someone on site to receive and check the delivery against your order. It's also worth double-checking ducting and electrical supply routes are prepared in advance, as most Harlequin plants require power for the blower unit.