If you've ever experienced a frustrating drop in water pressure when two taps or showers run at the same time, an accumulator vessel is one of the most effective and underrated solutions available. Unlike a pump, which actively boosts pressure, an accumulator works by storing a pressurised volume of cold mains water that can be released rapidly on demand — delivering a powerful surge of water the moment a tap opens, without waiting for the mains supply to catch up.
How Does an Accumulator Vessel Work?
An accumulator vessel is a sealed tank divided internally by a flexible membrane or bladder. One side of the membrane is pre-charged with air or nitrogen to a set pressure; the other side fills with mains cold water. When a tap or shower is opened and demand exceeds what the incoming mains supply can deliver alone, the pressurised water stored in the vessel is released instantly to make up the shortfall. The result is a strong, consistent flow at every outlet — even when multiple are running simultaneously.
Crucially, an accumulator does not increase the static pressure of your mains supply — it boosts the flow rate available on demand. If your incoming mains pressure is very low (below around 1 bar), an accumulator alone may not be sufficient and a pump or pump and accumulator combination may be required instead. If your mains pressure is adequate but flow rate drops when demand increases, an accumulator is typically the ideal fix.
Who Needs an Accumulator Vessel?
Accumulators are particularly well suited to properties with combination boilers that are sensitive to flow rate, homes with multiple bathrooms or showers in regular simultaneous use, properties where the incoming mains supply has adequate pressure but limited flow capacity, and any system where inconsistent hot water delivery is traced back to demand exceeding incoming supply. They are also commonly installed alongside unvented hot water cylinders and pump-assisted systems to smooth out demand peaks and reduce pump cycling.
Stuart Turner MainBoost
Stuart Turner is one of the most trusted names in water pressure management in the UK, and their MainBoost accumulator range reflects that pedigree. Designed for straightforward installation on the incoming cold mains supply, MainBoost vessels are compact, robustly built, and pre-charged ready for installation. Stuart Turner's reputation for reliability and their strong UK support network make MainBoost a popular choice for both installers and homeowners looking for a no-compromise solution.
OSO SuperStream
OSO's SuperStream accumulator vessels are a well-specified option combining quality construction with competitive sizing options. Designed to integrate neatly into a range of cold water supply configurations, SuperStream vessels are a solid choice for new-build and retrofit applications where consistent cold water delivery to an unvented cylinder or combination boiler system is a priority.
Salamander AccuBoost
Salamander are best known for their shower pump range, and their AccuBoost accumulator vessels are designed with the same focus on solving real-world low flow problems in UK homes. The AccuBoost range is particularly well suited to use alongside Salamander's pump products where a combined pump-and-accumulator approach is needed, though the vessels work equally well as a standalone solution. Available in a range of capacities, AccuBoost vessels are a popular choice for installers already specifying Salamander equipment.
Sizing Guide — How Big an Accumulator Do You Need?
As a general rule, the larger the vessel the greater the reserve of stored water available during peak demand. For a single bathroom property with a combi boiler, a 10–18 litre vessel is typically sufficient. For a two to three bathroom home with an unvented cylinder, 25–50 litres is more appropriate. For larger properties or commercial applications with high simultaneous demand, 100 litres or above may be required. If you're unsure which size is right for your property, contact our team for advice.
Browse our full range of accumulator vessels below.
