Common cold-water pipe materials, isolation, and why and where cold pipework must be protected from freezing.
Cold water pipework has to deliver wholesome water reliably, so the material, the joints, the supports and the frost protection all have to suit where the pipe runs.
Inside a dwelling, copper and plastic pipes such as polybutylene and cross-linked polyethylene are common. Underground, blue MDPE is the usual choice for the supply pipe. Each material has its own jointing methods, and pipe clips or supports must be spaced to suit the material so the pipe does not sag.
Fitting service (isolation) valves at appliances and key branches lets you shut off one fitting for maintenance without draining the whole system, which makes repairs quicker and cleaner.
Frost is the big enemy of cold pipework. Water expands as it freezes and can split a pipe or fitting, then cause flooding when it thaws. Pipes in lofts, garages and other unheated spaces, and the underground supply pipe, must be insulated and laid or routed to keep them out of the freezing zone.
Underground, the supply pipe is laid deep enough to stay below the frost line and clear of other services, with protection where it rises into the building.
Match material to location, support it correctly, give yourself isolation points, and protect against frost. Confirm material suitability and depth/insulation detail against current guidance.