Harlequin

Harlequin manufacture a broad range of polyethylene tanks including potable water storage, rainwater harvesting systems, septic tanks, and bunded oil and chemical tanks. Most are moulded in one piece using MDPE, giving a robust, corrosion-free tank suitable for above or below ground installation depending on the model. Check the individual product spec, as burial depth and inlet/outlet configurations vary across the range.

Many Harlequin tanks are specifically designed for underground installation, with ribbed or dimpled walls to resist ground pressure and a design depth stated in the product literature. You'll need to follow the manufacturer's installation guide closely, particularly around pea-shingle backfill, concrete surrounds where specified, and groundwater conditions. If you've got a high water table or vehicle loading above the tank, additional measures such as a concrete slab or traffic-rated cover may be required.

Sizing depends on roof catchment area, average rainfall for your region, and intended use — garden irrigation needs less storage than a system feeding toilets and a washing machine. A rough rule of thumb for domestic use is 5,000–7,500 litres, but larger commercial or agricultural applications may need considerably more. Our team can help you calculate a suitable size based on catchment and demand if you're unsure.

Harlequin septic tanks are manufactured to meet BS EN 12566-1 and carry the necessary CE/UKCA marking, but compliance also depends on correct installation, discharge consent, and — since the 2020 general binding rules — routing to a soakaway rather than a watercourse. If your septic tank discharges to a watercourse, you'll typically need to upgrade to a sewage treatment plant. Always check with your local Environment Agency office or building control before installation.

Larger Harlequin tanks are usually delivered on a kerbside pallet or crane-offload lorry, so you'll need suitable site access and enough manpower or machinery to move the tank into position — these are heavy, bulky items even when empty. Lead times vary by tank size and current stock levels, so it's worth confirming dispatch timescales before you commit to a groundworks date. Always inspect the tank on delivery for any transit damage before signing for it.

Bunded tanks have an integral secondary containment skin designed to hold 110% of the tank's capacity in the event of a leak, which is a requirement for oil storage near watercourses or in vulnerable groundwater areas. They still need a stable, level, load-bearing base — usually a concrete or paving slab — and should be sited with fire regulation separation distances from boundaries and buildings in mind. Check whether your specific model requires venting or an overfill alarm as part of a compliant installation.