Rubber Bladder for Vessels

A rubber bladder is the flexible membrane at the heart of an expansion vessel or pressure tank. It separates the water or fluid side from the pre-charged air or nitrogen cushion, absorbing volume changes caused by thermal expansion and maintaining stable system pressure. Replacing a worn or failed bladder restores full vessel performance without the need to replace the entire unit.

Material Options

EPDM (Ethylene Propylene Diene Monomer) is the standard choice for closed heating circuits and solar thermal systems. It offers excellent resistance to hot water, steam, and glycol-based fluids, and retains its elasticity across a wide temperature range. A high-temperature EPDM variant is available for solar thermal applications where fluid temperatures can exceed standard limits.

NBR (Nitrile Butadiene Rubber) is specified where compatibility with oils, fuels, or hydrocarbon-based fluids is required. NBR bladders are commonly used in industrial pressure vessels and fuel system accumulators where EPDM would degrade.

Size Range

Bladders are available in capacities from 8 L to 1000 L, covering the full range of common expansion vessel and pressure tank sizes used in residential, commercial, and light industrial installations. Each bladder is sized to match the internal geometry of the corresponding vessel, ensuring a proper seal and full working volume.

Potable Water Approved Options

Selected EPDM bladders carry WRAS (Water Regulations Advisory Scheme) and NSF 61 certification, confirming suitability for direct contact with drinking water. These approved variants are required for potable water pressure systems, boosting sets, and domestic hot water storage applications where regulatory compliance is mandatory.

High-Temperature EPDM for Solar Thermal

Solar thermal circuits can subject expansion vessels to fluid temperatures well above those found in conventional heating systems. The high-temperature EPDM variant is compounded to withstand continuous operating temperatures up to 120°C, preventing premature hardening, cracking, or loss of elasticity that would occur with standard-grade rubber.

Installation

All bladders feature a threaded neck attachment that secures directly to the vessel's internal fitting. This design ensures a reliable, leak-free seal and allows straightforward replacement without specialist tooling. Always depressurise the vessel and verify the replacement bladder matches the vessel's rated capacity and connection thread before installation.

Typical Applications

Rubber bladders are used across a broad range of fluid system applications:

• Closed heating circuits and underfloor heating systems
• Chilled water and cooling circuits
• Potable water pressure and boosting systems
• Solar thermal expansion vessels
• Industrial hydraulic accumulators and fuel system pressure vessels