A 600x450mm Solid Top Galvanised Double Seal Manhole Cover and Frame is a specialized, airtight access cover designed to seal underground inspection chambers and foul drainage pits located indoors, in enclosed areas, or close to living spaces.

Primary Uses & Key Features

• Indoor & Sensitive Location Drainage: Designed for installation inside buildings (such as garages, extensions, basements, and utility rooms) or directly adjacent to exterior doors and open windows where foul sewer odors must be completely contained.

• Double Seal Smell-Proofing: Features two continuous internal sealing channels—typically a combination of rubber gaskets, neoprene seals, or grease-filled grooves—that form a secondary barrier to guarantee a fully gas-tight and airtight fit.

• Corrosion-Resistant Steel: Manufactured from mild steel and hot-dip galvanised to BS EN ISO 1461 standards to withstand internal moisture, damp garage environments, and cleaning chemicals without rusting.

• Solid Anti-Slip Top: Built with a raised chequer-plate steel lid that provides a flat, secure walking or driving surface while preventing dirt, spills, or surface water from penetrating the underlying drainage chamber.

Available for collection from our Rugby branch or local delivery using our own fleet.

Delivery is kerbside and the final offloading position is always subject to safe access and the driver’s discretion.

Please tell us before delivery about:

• Narrow roads or restricted entrances
• Parked vehicles or limited turning space
• Overhead cables, trees or other obstructions
• Soft, sloping or unsuitable ground
• Any other access concerns

Enter your postcode on the product page to check your delivery area. We’ll confirm the delivery date after your order is placed.

How does a double seal system actually stop sewer gases?

The frame contains two parallel channels. The inner channel holds a continuous rubber gasket or grease seal, while the outer channel creates a secondary compression barrier. When the lid is bolted down, these dual contact points lock in foul smells and prevent sewer gases from leaking into surrounding living spaces.

Is a double seal cover required for indoor drainage chambers?

Yes. Under Building Regulations (Document H), any inspection chamber or manhole cover located inside a dwelling, garage, extension, or enclosed outbuilding must be double-sealed and screwed down to ensure an airtight seal against toxic sewer air.

Do you need to use grease in the frame channels during installation?

For non-gasketed double seal models, filling the inner frame groove with silicone grease or thick petroleum jelly creates the airtight barrier. Even for gasketed models, applying a thin layer of grease protects the rubber seals from drying out and sticking over time.

How do you lock down the double seal to ensure it stays gas-tight?

The cover is supplied with four corner locking screws. Tightening these bolts draws the solid steel lid evenly into the frame, compressing the dual sealing gaskets or grease channels tightly against the seat to maintain a permanent air- and water-tight seal.