A water pipe leak ranges from a drip under a sink (annoying, not urgent) to a burst under pressure (emergency, call now). Here’s how to tell the difference, what to do in either case, and typical Belfast repair costs.
Step 1: how bad is it
Emergency, call immediately:
- Water spraying under pressure
- Water coming through a ceiling
- Burst pipe audible (loud hissing or running sound inside a wall)
- Pressure drop across the whole house
- Water main leak: see Leaking water main in Belfast
Urgent, call within the hour:
- Persistent drip that won’t stop
- Boiler losing pressure fast
- Leak under floor or in a wall with no visible access
- Damp spreading across a ceiling or wall
Not urgent, book normal slot:
- Slow drip from a tap (needs a washer or cartridge)
- Slight dampness around a radiator valve
- Occasional drip from a toilet cistern
Step 2: stop the water
For most leaks:
- Turn off the mains stopcock (under kitchen sink, cupboard near front door, or under stairs)
- Open a cold tap on the ground floor to drain pressure
- Move electrics and valuables away from the leak
- Put buckets, towels or a plastic sheet to contain drips
For central heating leaks (radiator valve, boiler pipe):
- Turn off the heating at the thermostat / timer
- Close the valves either side of the leak (TRV one side, lockshield the other)
- Top up boiler pressure only if instructed (if pressure has crashed, leaving it low is often safer)
For hot water cylinder leaks:
- Turn off the boiler (so no more hot water pumps into the cylinder)
- Turn off the immersion heater (electric element on the side of cylinder)
- Turn off the cold feed to the cylinder (usually a valve near the top)
Step 3: find the source
Common leak points:
| Location | Likely cause |
|---|---|
| Under kitchen / bathroom sink | Tap washer, cartridge, waste trap, flex hose |
| Behind washing machine / dishwasher | Inlet hose, isolator valve |
| Around a radiator | Valve gland, radiator pinhole |
| Under boiler | Diverter valve, pump seal, auto-air vent |
| In the loft | Cold tank overflow, overflow pipe, tank itself |
| Toilet base | Pan connector, flush seal, overflow |
| From ceiling (room below bathroom) | Bath waste, shower tray seal, tile grout failure |
Step 4: DIY repairs (only if you know what you’re doing)
Reasonable DIY:
- Tap washer or cartridge: £5-£25 part, 30-60 min job, needs isolation valve under the sink
- Flexible hose replacement: £8-£25 part, 15 min job
- Radiator bleed valve tightening: one-eighth turn with a square key
- Immersion heater element: £25-£60 part, requires complete cylinder isolation + drain. Not recommended unless you’re confident
Not reasonable DIY:
- Soldered copper joint repairs (push-fit fittings are fine, soldering in a cupboard is a fire risk)
- Mains stopcock replacement
- Boiler internal leaks
- Under-floor pipe leaks (access issues)
- Any gas work (legally must be Gas Safe registered)
Typical Belfast repair costs (2026)
| Job | Typical total |
|---|---|
| Tap washer / cartridge replacement | £85-£140 |
| Waste trap replacement | £95-£160 |
| Flex hose replacement | £85-£120 |
| Radiator valve replacement | £120-£220 |
| Radiator body leak (small pinhole, replacement) | £180-£320 |
| Push-fit pipe repair (accessible) | £140-£240 |
| Under-floor pipe repair (access required) | £320-£580 |
| Boiler internal leak diagnosis | £95-£140 call-out + parts |
| Cylinder leak (needs replacement) | £1,200-£2,400 |
| Mains stopcock replacement | £95-£160 |
Insurance
Most buildings insurance covers damage caused by a leak (ceilings, walls, flooring). It usually does NOT cover:
- The pipe repair itself (wear and tear is excluded)
- Excess (£100-£500 typical)
- Gradual damage if you knew about the leak and delayed
Report to insurance within 48 hours. Take photos before, during, and after repair.
Prevention
- Know where your stopcock is and exercise it every 6 months
- Insulate exterior pipes and the loft tank before winter
- Service the boiler annually (catches valve seal degradation before it leaks)
- Replace washing machine / dishwasher hoses every 5-7 years
- Check under sinks quarterly for damp (daylight torch test)
Book a repair
For active leaks, phone is fastest. For non-urgent (suspected leak, damp spot investigation), send photos. We respond inside 2-4 hours in working hours across Belfast, Lisburn, Newtownabbey, Bangor.
Related services: Emergency Plumbing · Boiler Repair · Radiator Installation
Related guides: Leaking water main in Belfast · Radiators not heating up