Leaks rarely announce themselves with a burst. More often they appear as a damp patch under the sink, a green crust on copper, or the sound of dripping at night. Many common leaks can be fixed with basic tools. Start by checking visible pipework, tap washers and overflow joints, and always isolate the water before tight repairs.

Before you tackle any repair: isolate the water

Water off first, every time. Find your internal stopcock — usually under the kitchen sink, in an airing cupboard, or near the front door. Turn it clockwise until it stops. If you have a cold water tank, close the gate valve on the outlet pipe. Open the lowest tap to drain remaining water and confirm the supply is off.

• For hot water, switch off the boiler or immersion heater before draining.
• For electric showers, turn off the pull-cord isolator.
• Keep a bucket, old towels, a torch and a small mirror to hand.

Check visible pipework and joints first

Most leaks are found, not guessed. Dry every suspect joint with kitchen roll, then wrap a fresh piece of tissue around it. Wait a few minutes and check for dampness. On copper pipe, look for green verdigris or white limescale. On plastic pipe, check the pipe is pushed fully into the fitting and the collet is secure. Compression joints have a nut and olive; vibration can loosen them.

If a compression nut weeps, tighten it a quarter turn — no more. Overtightening can crush the olive. If that fails, isolate, drain, undo the joint, inspect the olive, and remake it. For threaded joints, wind PTFE tape clockwise three or four turns. For push-fit, release the collet, cut a fresh square end, add a pipe insert if plastic, and push it home. Never open a gas boiler casing; call a qualified gas engineer.

Tap washers and dripping taps

A dripping tap wastes water and stains the basin. Traditional taps usually need a new washer. Isolate the supply, plug the basin, unscrew the head, remove the retaining nut and lift out the spindle. The old washer sits at the bottom — take it to a merchant to match. Reassemble carefully, avoiding cross-threading.

Quarter-turn and mixer taps often use ceramic cartridges. Isolate, remove the handle, unscrew the cartridge and replace with an identical model. Check base and spout O-rings, common hidden drips. Under the sink, flexible connectors can weep at the fibre washer; tighten gently or replace. If the tap body is cracked, replacement is the sensible answer.

Overflow joints, toilets and cold water tanks

Water dripping from an overflow outside is a classic sign of a faulty float valve. In a cold water tank, the valve may let by because the washer has perished or the arm is set too high. Turn off the supply, fit a new washer or valve, and set the float so water stops about 25mm below the overflow. In a toilet cistern, the same valve controls the fill. If water runs into the pan, check the flush valve seal or float height.

For a leaking overflow joint, isolate and drain the cistern, clean the joint, and remake it with a new washer or silicone. Do not block an overflow pipe — it is a safety device. Close-coupled toilets can leak at the doughnut washer between cistern and pan. Tighten backnuts gently and evenly, or fit a new washer kit.

Tight repairs: compression, push-fit and sealants

Tight spaces are frustrating. A basin wrench, small adjustable spanner and head torch help. For a compression joint you cannot easily remake, dry it and apply a few wraps of PTFE tape around the olive before reassembling. For plastic push-fit, use the correct release tool rather than forcing the collet. For threaded plastic fittings, use PTFE tape or jointing compound, never both unless the manufacturer says so.

Self-amalgamating tape can seal a pinhole on copper as a temporary measure, but not permanently. If a pipe is blown or badly corroded, cut out the damaged section and replace it using compression or push-fit fittings. Support the pipe so the repair is not under strain. If unsure, stop and call a plumber — small leaks cause rot, mould and electrical damage.

Preventing leaks and knowing when to call a plumber

Prevention is simpler than repair. Lag exposed pipes in the loft and garage, insulate outside taps, and check under the sink and around the washing machine once a year. Fit isolating valves on tap and appliance supplies. Make sure everyone knows where the stopcock is and that it turns freely.

Call a professional for gas appliance leaks, unvented cylinders, mains stopcock problems, leaks behind solid walls, or any repair where you cannot safely isolate the water. A plumber can pressure-test the system and find hidden leaks with minimal damage. A slow drip adds to your water bill and quietly damages your home. With preparation, most common leaks are within reach of a careful DIY repair.