Siphonic Roof Drain Outlets

Engineered Roof Drain Outlets

Each outlet is matched to the system design and fused to HDPE pipework, ensuring airtight joints, low maintenance and reliable performance during extreme rainfall events on commercial and industrial buildings.

Our HDPE siphonic drainage systems are ideal for large commercial buildings, airports, stadiums, and industrial facilities where rapid rainwater removal is critical.

Advantages

Higher flow capacity with smaller pipes
Fewer downpipes required
No pipe slope needed - horizontal installation
Reduced material and installation costs
Self-cleaning action prevents blockages

Applications

Airports

Large terminal buildings requiring efficient rainwater management.

Warehouses

Industrial and logistics facilities with large roof areas.

Siphonic Roof Drain Outlets at Full-Bore Velocity

Siphonic systems drain large roofs with a fraction of the pipework of gravity systems - but only when engineered precisely. Our BS EN 12056 designs deliver full-bore flow with balanced collector geometry.

Effective drainage engineering is about managing peak events, not average flow. Our systems are hydraulically modelled against design storm scenarios, with pipe sizing, gradient and access point spacing optimised to carry cloudburst loads without surcharge or sediment settlement.

Smooth-bore HDPE delivers a Manning coefficient around 0.009 - significantly better than concrete - which allows smaller diameters or flatter gradients for the same discharge capacity. Combined with chemical resistance against sewage aggressors, this keeps buried assets serviceable for over fifty years.

High Flow Capacity

Smooth bore walls reduce friction losses and maintain design velocity

Ring-Stiffness Options

SN4 to SN8 buried grades engineered for traffic load conditions

Chemical Immunity

Resists hydrogen sulphide attack and aggressive soil chemistry

Siphonic Expertise

Full-bore siphonic roof and ground drainage designed to BS EN 12056

Joint Integrity

Fusion-welded or rubber-ring joints sealed against infiltration and exfiltration

Long Service Life

50+ year design life with negligible maintenance intervention