Heating & Hot Water · 6 min read · Beginner

Hot-Water Cylinder & Pipe Insulation: Simple Heat-Loss Improvements

Reduce heat loss from older hot-water cylinders and exposed hot-water pipes while keeping controls and safety components accessible.

Key points & steps

Identify whether the cylinder is factory-insulated foam or an older type using a removable jacket. Modern cylinders may already have substantial integral insulation.
If using a separate jacket, select one designed for the cylinder size and fit it without covering thermostats, labels, immersion-heater heads or safety controls that need access.
Insulate accessible hot-water pipework with correctly sized pipe insulation, prioritising hotter runs near the cylinder and pipes through unheated spaces.
Mitre or carefully join insulation around bends so large bare sections are not left at elbows and valves.
Do not insulate components that manufacturers require to remain visible or uninsulated, and keep discharge/safety arrangements unobstructed.
Check the cylinder thermostat/control strategy at the same time; insulation reduces heat loss but does not correct unsafe or inefficient control settings.
Inspect insulation periodically after plumbing work because pipe lagging is often removed for access and not reinstated.

A poorly insulated older cylinder can be a cheap target for improvement compared with replacing the entire hot-water system.
Use pipe insulation with an internal diameter matching the pipe rather than leaving a large air gap around it.
Hot-water storage temperatures have hygiene/safety implications; do not reduce cylinder temperature simply as an energy-saving shortcut without proper guidance.