Drainage air admittance valve McAlpine MP50-50C-PB 50 mm for plumbing ventilation

McAlpine MP50-50C-PB is a 50 mm drainage air admittance valve engineered for plumbing ventilation in domestic and light commercial installations. The valve admits air into drain systems to equalize pressure and prevent negative pressure from siphoning trap seals, while also providing a one-way barrier against sewer gases entering the building. Designed to fit standard 50 mm pipe connections, it can be used in both new installations and retrofits where traditional external venting is impractical.

Advantages

The valve provides reliable pressure balancing in drainage systems without the need for roof penetrations. Its compact 50 mm connection simplifies installation into existing soil and waste stacks or branch fittings. The one-way sealing mechanism helps maintain trap water seals and reduces the risk of sewer gas ingress. Constructed for use in typical domestic and light commercial environments, the component supports improved drainage performance and quieter venting compared with unvented systems.

Suitable for

• Domestic and light commercial drain and soil stacks with 50 mm pipework
• Retrofit installations where roof venting is not feasible
• New builds requiring concealed or internal ventilation solutions
• Situations needing protection of trap seals from negative pressure

Key specifications

• Connection size: 50 mm
• Function: Air admittance (one-way air inlet and gas barrier)
• Intended application: Drainage and plumbing ventilation
• Suitable environments: Domestic and light commercial
• Installation type: Inline or branch fitting for soil and waste systems

How to use

Install the valve on a vertical branch or soil stack at a point accessible for service, ensuring the connection matches 50 mm pipework and the valve is oriented per manufacturer guidance. The unit should be fitted above the highest fixture served or in accordance with local plumbing codes to allow air admission while maintaining trap seals. After installation, check for secure joints and test fixtures to confirm proper drainage and absence of sewer gas odors. Follow all applicable standards and regulations for plumbing ventilation in your jurisdiction.

Usage recommendations

Use this valve where traditional external venting is impractical, and confirm compatibility with local plumbing codes. Periodic inspection is advised to ensure the valve operates freely and maintains a tight seal against sewer gases.