Vaillant Pressure Relief Valve 3Bar 17-8985 178985

Vaillant Pressure Relief Valve 3Bar 17-8985 178985

The Vaillant Pressure Relief Valve (Part No. 178985) is a critical safety component designed to protect the boiler and the wider heating system from excessive internal pressure. Pre-set to 3 Bar, the valve is engineered to open and discharge water through a dedicated pipe (tundish) if the system pressure exceeds a safe limit. This prevents damage to the heat exchanger, pipework, and other hydraulic components.

This part is also commonly identified by the reference 17-8985.

Key Features and Specifications
Fixed Pressure Setting: Set to discharge at 3 Bar (0.3 MPa), the industry standard for domestic sealed heating systems.

Genuine Vaillant Part: Manufactured to the exact specifications required for Vaillant hydraulic blocks, ensuring a perfect seal and reliable "crack" pressure.

Corrosion Resistant: Constructed with a high-grade brass body and a durable internal spring mechanism designed for long-term reliability in wet environments.

Safety Essential: Acts as the final line of defense against system over-pressurization, often caused by a failed expansion vessel or a leaking filling loop.

Direct Replacement: This is the authorized replacement for the PRV found across the ecoTEC and ecoFIT ranges.

Boiler Compatibility
This Pressure Relief Valve (PRV) is used in almost all modern Vaillant wall-hung boilers. Compatible models include:

ecoTEC Plus: 412, 415, 418, 428, 438, 612, 615, 618, 624, 630, 637, 824, 831, 837, 937.

ecoTEC Pro: 24, 28, 30.

ecoFIT Pure: 412, 415, 418, 425, 430, 435, 612, 615, 618, 625, 630, 825, 830, 835.

Home Glow: Various system and combi models.

Technical Tip: If your boiler is leaking water from the small copper pipe on the outside wall, the PRV has likely opened. While this can happen due to a one-time pressure spike, persistent dripping usually means the valve's seat is contaminated with debris or the Expansion Vessel has lost its charge.

Maintenance and Installation Advice
Replacing the PRV requires the boiler to be fully drained. It is a "plug-and-play" component held in place by a retaining clip. When replacing the valve, it is essential to check the Expansion Vessel pressure, as a failed vessel is the most common reason for a PRV to blow. Always ensure the discharge pipework is clear and correctly terminated to a safe, visible location outside.

Essential Companion Products
To resolve persistent over-pressurization issues, the following genuine Vaillant parts are often checked or replaced alongside the PRV:

Direct Product Link: Vaillant Pressure Relief Valve - 178985

The Root Cause: Vaillant Expansion Vessel - 181051

Pressure Monitoring: Vaillant Water Pressure Sensor - 0020059717

Air Removal: Vaillant Automatic Air Vent - 0010033857

Specialist Support and Local Collection
Is your boiler pressure constantly rising or is the valve dripping? Our trade counter team can help you diagnose whether you need just the PRV or if your expansion vessel also requires attention.

Visit our trade counter and Bathroom Showroom at 61 Fullers Road, E18 2QB for expert technical advice and immediate access to genuine Vaillant spares.