Frozen pipes in London

Thames Water's steps are simple. Turn off the stop valve by turning it clockwise. Open the taps so water can escape when the pipe thaws. Take off any lagging and move anything you want to keep dry. Warm the pipe slowly with a wrapped hot water bottle or warm towels.

Do not use a blowtorch, heat gun or any naked flame. In old London houses the pipes are often near timber floors and lath walls, and a flame can start a fire inside a void you cannot see. When the pipe has thawed, run a dry cloth along it. If it gets wet, there is a leak, so leave the water off and call a plumber.

Modern condensing boilers have a small plastic condensate pipe that often runs outside. When it freezes, the boiler can lock out. Pouring warm, not boiling, water over the outside section can thaw it. If the boiler still will not restart, or you need anything done on the boiler itself, that is a job for a Gas Safe registered engineer.

Lag pipes in lofts and on outside walls with foam insulation. Fit an isolation valve inside for any outside tap and drain it before winter. If you are going away, leave the heating on low. The Leasehold Advisory Service gives the same advice for leaseholders, because a burst in an empty flat can flood the flats below before anyone notices.

A lot of London flats sit empty for a few days at a time, between tenants, over Christmas or as short lets. That is when a frozen pipe does most damage, because the leak starts on the thaw and nobody is there to turn it off. If a flat will be empty in cold weather, leave the heating on a low setting, turn the stop tap off if the heating is not needed for anything else, and ask a neighbour or the managing agent to look in. Some home insurance policies limit cover for escape of water if a home is left unoccupied for a set number of days, so check yours.