Harmer SML Below-Ground Drainage is a trusted soil and waste system from Alumasc Water Management Solutions (AWMS), designed for demanding projects where performance, reliability, and ease of installation are critical.

Designed to allow direct connection from soil to drain to sewer, Harmer SML Below-Ground Drainage brings together advanced cast iron technology with a lightweight, dry-jointed design to support efficient specification and straightforward installation across a wide range of building types.

Performance and Compliance

Manufactured and tested in accordance with BS EN 877, Harmer SML Below-Ground Drainage meets the requirements of both CE Marking under the Construction Products Regulation, and Kitemark certification, giving specifiers confidence in product quality and regulatory compliance.

Produced under strict factory-controlled conditions to ISO 9001, the system is engineered to perform in demanding below-ground environments, where drainage components must withstand aggressive effluents, chemical exposure and long-term mechanical stress. Pipes are available in standard 3-metre lengths with diameters ranging from 100mm to 400mm, for flexible system design.

In addition to structural strength, Harmer SML offers excellent acoustic performance, with noise attenuation tested to BS EN 14366, making it suitable for residential, commercial and mixed-use developments.

Installer Benefits

Harmer SML combines traditional strength with a lighter, more manageable system to facilitate quicker handling on site. The socketless, dry-jointed design allows secure connections between pipes and fittings without specialist tools, helping installers achieve reliable results efficiently.

Essential accessories are available, whilst a comprehensive suite of fittings and specialist components enables installers to address complex layouts and site constraints. Inspection chambers are also available in a range of formats, for easy access and maintenance.

The system is fully compatible with the Harmer SML Above-Ground range, enabling continuity throughout the building envelope and simplifying coordination between above- and below-ground drainage design.

Advanced Protection

Harmer SML pipes are externally protected with an anti-corrosive primer and a two-part epoxy coating, while interiors feature a high-performance epoxy lining that provides resistance to chemical attack and mechanical damage. Fittings receive internal and external epoxy coatings to ensure consistent protection throughout the system.

These coatings go beyond the minimum requirements of BS EN 877, supporting long-term performance even when exposed to aggressive cleaning agents and domestic effluents.

The Benefits of Cast Iron

The use of cast iron, manufactured to EN 1561 with a minimum grade of EN-GJL-150, ensures high tensile strength and excellent load-bearing capability. As a non-combustible material with an A1 fire classification, cast iron also supports fire safety strategies without the need for additional fire protection collars.

Cast iron’s low thermal expansion and exceptional stability give it a natural resistance to deformation, maintaining structural integrity far better than plastic. Its low coefficient of thermal expansion, ensures SML pipework remains dimensionally stable under temperature variation and extremes, eliminating the need for expansion joints or special movement provisions.

Harmer SML Below-Ground Drainage is 100% recyclable system with a long-life cycle of 40 years. All waste can be returned to the furnace to make new cast iron products, reducing the system’s environmental impact, and maximising life cycle value.

The system is further supported by Alumasc’s nationwide network of technical experts, ensuring long-term peace of mind for clients and building-users alike.

Harmer Building Drainage sits under the AWMS umbrella together with Alumasc Rainwater Gutters & Downpipes; Skyline Architectural Aluminium; Wade Building Drainage; and Gatic Civil Drainage & Access Covers. All five brands are well known for innovation, quality and longevity.

Download the Harmer SML Brochure here

For further information, call 01536 383810 or visit https://www.alumascwms.co.uk