Air admittance valve McAlpine HC50-50 Ø50 mm for drainage and ventilation systems

McAlpine HC50-50 is an air admittance valve with a Ø50 mm connection designed for drainage and ventilation systems. The compact valve admits air into plumbing stacks and branch drain lines to equalize internal pressure, reducing the risk of trap siphoning and helping maintain water seals. It is intended for domestic and light commercial installations where a mechanical vent is appropriate and connects directly to 50 mm pipework.

Advantages

The valve offers a compact design that fits within confined service voids and under fixtures. It operates without a roof penetration, removing the need for conventional vent stacks in many retrofit and new build scenarios. The construction provides reliable air intake under negative pressure while preventing the escape of sewer gases when pressure is neutral or positive. Installation requires minimal adjustments and routine maintenance is limited to visual checks and occasional cleaning.

Suitable for

• Domestic drainage systems with 50 mm pipework
• Light commercial washrooms and sanitary fittings
• Retrofit projects where roof venting is impractical
• Locations requiring a mechanical alternative to open vent stacks

Key specifications

• Connection diameter: 50 mm
• Function: air admittance to equalize pressure in drainage systems
• Application: drainage and ventilation for traps and stacks
• Typical installation: vertical or as specified by manufacturer guidance
• Construction: compact body suited to confined spaces

How to use

Fit the valve onto compatible 50 mm pipework following plumbing regulations and manufacturer guidance for orientation and location. Ensure the valve is accessible for inspection and positioned above the highest fixture served where practical. After installation, test the system by running fixtures to confirm trap seals remain intact and that air is admitted correctly when fixtures discharge. Replace the unit if signs of damage or persistent odour are detected.

Usage recommendations

Use the valve in accordance with local plumbing codes and the manufacturer's installation instructions. Avoid fitting in locations subject to constant positive pressure or where exposure to external weather could affect operation. For mixed-material systems, ensure compatible connections and consider periodic inspection to verify continued airtight seating and functionality.