List of products by brand Harmer Building Drainage

Shop Harmer flat roof outlets, floor drains and balcony drainage at The Gutter Centre. Part of Alumasc, Harmer offers high-performance aluminium, cast iron and stainless steel outlets for flat roofs, podium decks, terraces and internal wet areas.

Shop Harmer roof outlets, floor drains and balcony drainage online at The Gutter Centre. Harmer, part of Alumasc Water Management Solutions, is a market leader in engineered building drainage for commercial, residential and public-sector buildings. We supply Harmer high-capacity roof outlets, floor drains, balcony and terrace outlets, and cast aluminium drainage products designed for long-term durability and efficient water management.

Made from aluminium, cast iron and stainless steel, Harmer drainage products offer excellent corrosion resistance and high hydraulic performance. Engineered outlet bodies, secure clamping rings and precision-made components give reliable, watertight performance on flat roofs, podium decks, balconies, wet rooms and busy internal areas.

Harmer Flat Roof Outlets

Harmer flat roof outlets remove rainwater efficiently from warm roof, cold roof and inverted roof build-ups. Their hydraulically designed sumped bodies give high flow rates while protecting the integrity of the waterproofing membrane.

Key Benefits

  • Aluminium, cast iron or stainless steel bodies for long-term durability
  • High-capacity sump designs reduce ponding and roof loading
  • Secure clamping systems compatible with a wide range of waterproofing membranes, including single ply, bituminous and liquid-applied systems
  • Vertical, horizontal (spigot) and parapet outlet options
  • Lightweight aluminium options for fast installation

Harmer roof outlets are widely used on commercial roofs, apartment buildings, schools and public-sector developments.

Harmer Floor Drains and Gullies

Harmer floor drains and gullies remove water efficiently from internal areas such as plant rooms, commercial kitchens, washrooms, showers and utility areas. Smooth internal surfaces and stainless steel components support hygiene and make maintenance easy.

Performance Advantages

  • Available in aluminium, cast iron or stainless steel
  • Trapped and untrapped options
  • Removable gratings for easy cleaning
  • Suitable for concrete, screed and tiled floors
  • Gratings designed to resist blockages in busy areas

Harmer floor drains are commonly installed in leisure centres, restaurants, healthcare facilities and busy commercial buildings.

Harmer Balcony and Terrace Drainage

Harmer balcony outlets, spigot outlets and terrace drainage products remove rainwater from balconies, podium decks and roof terraces. Lightweight cast aluminium options give a long service life, excellent corrosion resistance and a clean architectural finish, and can be colour-coated to suit the building design.

They're especially well suited to contemporary residential and mixed-use developments where looks and longevity matter.

Why Choose Harmer Drainage?

  • High hydraulic performance across roof, terrace and floor drainage
  • Durable aluminium, cast iron and stainless steel construction
  • Compatible with a wide range of flat roof waterproofing systems
  • Lightweight options for easier installation
  • Precision-engineered for watertight reliability
  • Suitable for commercial, residential and industrial buildings

At The Gutter Centre, we supply Harmer roof outlets, floor drains and balcony drainage with nationwide delivery. Need help choosing the right Harmer outlet for your roof build-up or

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Harmer Cast Iron Grate - Square Heavy Duty Grate 323mm x 323mm

Cast Iron Grate - Square Heavy Duty Grate 323mm x 323mm available in 4" NPSM Threaded Ductile Iron with trap and 100mm Outlets.
Code: S300/DI/4/T
From
£308.18 Ex VAT£369.82 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Vertical Large Sump Square Grate & Adjustable Extension

Cast Iron Trapped Vertical Large Sump with Square Flat Grate & Adjustable Extension available in 225mm x 225mm Stainless Steel with BSP connection and 100mm & 150mm Outlets.
Code:
From
£265.51 Ex VAT£318.61 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Horizontal Medium Sump Square Grate & Adjustable Extension

Cast Iron Trapped Horizontal Medium Sump with Square Flat Grate & Adjustable Extension available in 225mm x 225mm Stainless Steel with BSP connection and 50mm, 75mm & 100mm Outlets.
Code:
From
£425.02 Ex VAT£510.02 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Vertical Medium Sump Square Grate & Adjustable Extension

Cast Iron Trapped Vertical Medium Sump with Square Flat Grate & Adjustable Extension available in 225mm x 225mm Stainless Steel with BSP connection and 50mm, 75mm & 100mm Outlets.
Code:
From
£383.85 Ex VAT£460.62 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Vertical Medium Sump Square Grate & Adjustable Extension

Cast Iron Non-Trapped Vertical Medium Sump with Square Flat Grate & Adjustable Extension available in 225mm x 225mm Stainless Steel with SPIGOT connection and 50mm, 75mm & 100mm Outlets.
Code:
From
£395.21 Ex VAT£474.25 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Vertical Large Sump Square Grate & Adjustable Extension

Cast Iron Trapped Vertical Large Sump with Square Flat Grate & Adjustable Extension available in 323mm x 323mm Sherardized Ductile Iron with BSP connection and 100mm & 150mm Outlets.
Code:
From
£135.19 Ex VAT£162.23 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Vertical Large Sump Square Grate & Adjustable Extension

Cast Iron Trapped Vertical Large Sump with Square Flat Grate & Adjustable Extension available in 225mm x 225mm Sherardized Ductile Iron with BSP connection and 100mm & 150mm Outlets.
Code:
From
£158.26 Ex VAT£189.91 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Horizontal Medium Sump Square Grate & Adjustable Extension

Cast Iron Trapped Horizontal Medium Sump with Square Flat Grate & Adjustable Extension available in 225mm x 225mm Sherardized Ductile Iron with BSP connection and 50mm, 75mm & 100mm Outlets.
Code:
From
£229.66 Ex VAT£275.59 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Vertical Medium Sump Square Grate & Adjustable Extension

Cast Iron Trapped Vertical Medium Sump with Square Flat Grate & Adjustable Extension available in 225mm x 225mm Sherardized Ductile Iron with BSP connection and 50mm, 75mm & 100mm Outlets.
Code:
From
£187.82 Ex VAT£225.38 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Vertical Medium Sump Square Grate & Adjustable Extension

Cast Iron Non-Trapped Vertical Medium Sump with Square Flat Grate & Adjustable Extension available in 225mm x 225mm Sherardized Ductile Iron with SPIGOT connection and 50mm, 75mm & 100mm Outlets.
Code:
From
£199.32 Ex VAT£239.18 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Vertical Large Sump Circular Grate & Adjustable Extension

Cast Iron Trapped Vertical Large Sump with Circular Flat Grate & Adjustable Extension available in 220mm Sherardized Ductile Iron with BSP connection and 100mm & 150mm Outlets.
Code:
From
£290.56 Ex VAT£348.67 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Non-Trapped Vertical Medium Sump with Circular Flat Grate

Cast Iron Non-Trapped Vertical Medium Sump with Circular Flat Grate available in 220mm Sherardized Ductile Iron with Spigot connection and 50mm, 75mm & 100mm Outlets.
Code:
From
£126.79 Ex VAT£152.15 Inc VAT
Est. delivery Wed 18th Nov
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Harmer 200 x 200mm Tile Bezels - Concentric Ring Grate BSP Connection

200 x 200mm Tile Bezels - Concentric Ring Grate available in 4" NPSM Threaded with a choice of Satin Stainless or Nickel Bronze with Removable Bottle Trap
Code:
From
£160.39 Ex VAT£192.47 Inc VAT
Est. delivery Wed 18th Nov
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Harmer Cast Iron Non Trapped Vertical Medium Sump with Circular Flat Grate

Cast Iron Non Trapped Vertical Medium Sump with Circular Flat Grate available in 220mm Sherardized Ductile Iron with BSP connection and 50mm, 75mm & 100mm Outlets.
Code:
From
£113.42 Ex VAT£136.10 Inc VAT
Est. delivery Wed 18th Nov
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