Vaillant Expansion Vessel 181051 18-1051

Ecotec Plus 624 VU 246 3-5

The Vaillant Expansion Vessel (Part No. 181051) is a critical safety and functional component within the boiler’s sealed primary heating circuit. As water is heated, it expands; this vessel contains a flexible internal rubber diaphragm and a pressurized air chamber that "absorbs" that increased volume. Without a functional expansion vessel, the heating system would experience rapid, dangerous pressure spikes every time the boiler fires, leading to leaks and component failure.

This part is also commonly identified by the reference 18-1051.

Key Features and Specifications
Large Capacity: Engineered to accommodate the expansion of water for typical domestic heating systems (radiators and underfloor heating).

Genuine Vaillant OEM: Manufactured to the exact dimensions, thread specifications, and pressure ratings required for a seamless fit behind the boiler's combustion chamber.

Pre-Pressurized: Supplied with a factory air charge (usually 0.75 to 1.0 bar), ready for installation and final adjustment by an engineer.

High-Grade Diaphragm: Features a durable, heat-resistant internal membrane designed to prevent the air and water from mixing, ensuring long-term pressure stability.

Corrosion Protection: The external steel shell is coated with a high-quality finish to resist the humid environment inside the boiler casing.

Boiler Compatibility
This vessel is a standard replacement for many of Vaillant's most popular wall-hung boilers. Common compatible models include:

ecoTEC Plus: 824, 831, 837 (VUW 246/3-5, 316/3-5, 376/3-5).

ecoTEC Pro: 24, 28 (VUW 246/3-3, 286/3-3).

ecoMAX: Various 800 series models.

Note: While it fits many models, always verify against your boiler’s 7-digit serial number, as some newer "ecoFIT" or compact models may require a differently shaped vessel.

Technical Tip: Is your boiler pressure gauge rising into the "red" zone (above 2.5 bar) when the heating is on, only to drop to zero when it cools down? This is the classic symptom of a failed expansion vessel. If you see water dripping from the Schrader valve (the air charging point), the internal diaphragm has perished and the vessel must be replaced.

Maintenance and Installation Advice
Replacing the expansion vessel is a significant task that usually requires the boiler to be partially dismantled and fully drained. It is located at the rear of the appliance. Important: Before condemning a vessel, a Gas Safe engineer will check the air charge; sometimes the vessel simply needs re-pressurizing with a pump rather than a full replacement.

Essential Companion Products
To resolve persistent pressure issues, the following genuine Vaillant parts are often replaced alongside the expansion vessel:

Direct Product Link: Vaillant Expansion Vessel - 181051

Safety Relief: Vaillant Pressure Relief Valve (3 Bar) - 178985

Pressure Monitoring: Vaillant Water Pressure Sensor - 0020059717

Air Removal: Vaillant Automatic Air Vent - 0010033857

Specialist Support and Local Collection
Are you struggling with an "F.22" or "F.75" fault code? These are frequently linked to expansion and pressure issues. Our trade counter team can help you identify if this vessel is the correct solution for your boiler model.

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