Tanks & Cylinders

Unvented hot water cylinders — such as Megaflo, Heatrae Sadia, and Vaillant uniSTOR — and traditional vented cylinders behave very differently when they develop a fault, and so do gravity-fed cold water storage tanks in the loft. Unvented cylinder work is legally restricted to qualified plumbers holding the relevant Part L qualification, but understanding how your system works can help you explain the fault clearly and avoid being overcharged. These guides explain how each system type works, how to diagnose common problems, when the pressure relief valve discharging is normal, and when it signals a serious fault.