Leak in the Loft? Tanks, Pipes and Condensation

In many houses the cold water storage tank sits in the loft and feeds the bathroom and the hot water cylinder. Beside it a smaller feed and expansion tank tops up an open-vented heating system. Both have a float valve, an overflow pipe to the outside and a lid that should fit. Pipes cross the loft floor to the bathroom, an en suite or a shower pump. A float valve that sticks, a tank that has split or a joint that has weeped for years all end up as a stain on the ceiling below. So does an overflow that drips inside the roof space.

Not every wet loft is a plumbing problem. On cold nights warm air from the house rises into the loft and condenses on the underside of the roof felt, then drips onto the insulation. That shows as scattered damp spots across a wide area, worst in winter, with no pipe nearby. Rain coming through a slipped tile, a cracked flashing or a worn chimney back gutter is a job for a roofer, not for us. We say so plainly. The job of the survey is to say which of these it is, so the right trade is called once.

The check starts with a careful look at the tank and its lid, the float valve and the overflow outlet outside. Every joint on the pipe runs and the insulation under them is checked too. A moisture meter on the ceiling below and on the joists shows where the water has reached. The thermal imaging camera picks out hot pipe runs to the bathroom and any cold wet patch spreading from one. The pipework is pressure tested where a hidden joint is a suspect. A test strip tells mains water from heating water, which separates the storage tank from the expansion tank.

Winter brings its own risk. Pipes and tanks in a cold loft can freeze, and a joint that has frozen and thawed may leak for weeks afterwards. Keeping the loft hatch closed, lagging the pipes and leaving the tank lid on all help in general terms. If a loft pipe or tank is the cause, we repair it in copper or barrier pipe if you want us to. The report records what was found with photographs and readings. Where a ceiling has been damaged, that report supports a trace and access or escape of water claim.