The plumbing problems most likely to get worse overnight are slow leaks you cannot see, drips landing on ceilings, cisterns that keep overflowing and pipes exposed to freezing weather. They get worse mainly because nobody is watching them for several hours.
Knowing which faults behave this way helps you decide what to check before bed.
Slow Leaks and Hidden Drips
A small leak from a pipe joint under the floor, behind a bath panel or inside a kitchen unit may only release a little water at a time. Over a whole night, though, that water can soak into floorboards, plaster and cupboard bases. By morning, a small damp patch can turn into a stain on the ceiling below.
A drip that is already landing on a ceiling is a particular concern. Plasterboard and older ceilings can absorb water until they sag. If you notice a ceiling bulging, keep people out of the room underneath. In flats and terraced houses, water can also travel into a neighbouring home, which is another reason not to leave a known leak running.
Overflows, Appliances and Backing Up
A toilet cistern that does not shut off properly may send water through the overflow all night. On a metered supply that wastes water and money, and if the overflow pipe is blocked or poorly fitted, the water may end up somewhere it should not.
Appliances left running overnight are another risk. If a washing machine or dishwasher hose has started to leak, running it while everyone is asleep gives the leak hours to spread. If you suspect a problem, leave the appliance off until it has been checked.
Waste water is a different concern. A toilet or sink that is starting to back up may get worse if it is used again before bed, so it is better left unused until it has been looked at.
Cold Nights and Exposed Pipes
On very cold nights, pipes in lofts, garages, outside walls and under suspended floors can freeze. A frozen pipe may not leak straight away, but ice can split it, and the leak often shows when it thaws. Thames Water advises insulating pipes, including outdoor ones, to reduce this risk.
If a pipe is frozen, avoid using a naked flame to thaw it. Warm the area gently and get the pipe checked if you are unsure whether it has been damaged.
Checks Before Bed
If you have noticed anything unusual during the day, a quick look before bed can save trouble. Check under sinks, around the toilet and near any appliance that has been used. Listen for water running when nothing is turned on.
If you find a leak, close the isolation valve for that fitting or the stopcock, as long as it turns without force, and put a container under any drips. Where water cannot be stopped or is near electrics, it should not be left until morning. For a fuller look at deciding what can wait, see our advice on plumbing problems outside normal hours in Oxford.