Hidden water leaks are sneaky. They can run for weeks or months before you notice, causing damage and hiking up your water bill. Here’s how to spot leaks early, what you can check yourself, and when to call a professional.
Warning Signs of Hidden Leaks
Higher Water Bills
If your bill jumps without an obvious reason (no extra people, no lifestyle change), you might have a leak. Even a small constant drip can waste hundreds of litres per week.
Damp Patches or Stains
Look for:
- Discolouration on ceilings or walls
- Wet patches on floors or carpets
- Peeling paint or wallpaper
- Bubbling plasterwork
Check under sinks, behind toilets, near radiators, and in airing cupboards.
Mould or Mildew
Mould thrives in damp conditions. If you have persistent mould in unusual places (not bathrooms or kitchens), suspect a leak.
Hissing or Dripping Sounds
Listen for running water when all taps and appliances are off. Check:
- Behind walls where pipes run
- Under floors
- In the loft
- Near the boiler or hot water cylinder
Reduced Water Pressure
A sudden drop in water pressure can indicate a leak in the supply pipe. If only hot water pressure drops, check the hot water cylinder and pipework.
Unexplained Wet Patches Outside
Soggy ground, pooling water, or unusually green grass in one area can signal an underground leak in your supply pipe.
DIY Leak Detection
Before calling a plumber, try these simple checks.
The Meter Test
If you have a water meter, this test confirms whether you have a leak:
- Turn off all taps, appliances, and the boiler
- Check your water meter and note the reading
- Wait 2 hours without using any water
- Check the meter again
If the reading has changed, you have a leak.
Visual Inspection
Check common leak spots:
Under sinks: Look for drips from pipes, P-traps, or supply connections.
Around toilets: Check the base for water pooling. Listen for running water in the cistern (faulty flush valve).
Behind appliances: Pull out the washing machine and dishwasher to check hoses and connections.
Radiators: Look for rust stains, drips, or damp patches on the floor beneath radiators.
Boiler and hot water cylinder: Check for drips from the pressure relief valve, pipework, or the base of the cylinder.
Loft: Check for wet insulation, drips from the roof, or damp around cold water tanks.
Toilet Cistern Test
Toilets are a common culprit for hidden leaks. The flush valve can fail, causing water to constantly run into the bowl.
Test: Add food colouring to the cistern. Wait 30 minutes without flushing. If colour appears in the bowl, the flush valve is leaking.
Radiator Pressure Test
If your heating system loses pressure regularly, there’s a leak somewhere.
Test: Top up the system pressure to 1.5 bar, then check it daily. If it drops more than 0.2 bar per week, you have a leak (in the boiler, radiators, or pipework).
When You Can Fix It Yourself
Some leaks are DIY-friendly:
Dripping tap: Usually a worn washer. Turn off the water, dismantle the tap, and replace the washer (available from hardware stores).
Loose pipe connection: If a compression fitting is dripping, tighten it with a wrench. Don’t overtighten or you’ll crack the fitting.
Leaking toilet flush valve: Replace the valve (around £10-£20). Turn off the water, drain the cistern, remove the old valve, fit the new one.
Leaking radiator valve: If the valve gland is dripping, tighten the gland nut. If the valve itself is leaking, you’ll need to replace it (best left to a plumber unless you’re confident).
When to Call a Professional
Some leaks need a plumber:
Behind walls or under floors: You can’t access these without causing damage. A plumber has leak detection equipment (thermal imaging, acoustic sensors, tracer gas).
Boiler or hot water cylinder leaks: Gas and pressurised systems need a Gas Safe registered engineer.
Underground supply pipe leaks: If the leak is between the water main and your property, you’re responsible for repair. This needs excavation and specialist equipment.
Persistent system pressure loss: If your heating system keeps losing pressure despite no visible leaks, there’s a hidden leak in the pipework or boiler.
Multiple leaks or widespread damage: If you’re finding leaks in several places, the problem might be bigger (corrosion, poor installation, frozen pipes). A plumber can assess the system.
You’re unsure or uncomfortable: If you’re not confident diagnosing or fixing the leak, call a professional. A small leak can become a big problem if mishandled.
Professional Leak Detection Methods
When you call a plumber for leak detection, they might use:
Thermal Imaging
A camera detects temperature differences in walls, floors, and ceilings. Leaks show up as cold spots (cold water) or warm spots (hot water or heating pipes).
Cost: £150-£300 depending on property size.
Acoustic Leak Detection
Sensitive microphones detect the sound of water escaping from pipes, even behind walls or underground.
Cost: £150-£250.
Tracer Gas Detection
A non-toxic gas is added to the water system. The gas escapes at the leak point and is detected with a sensor. Useful for finding leaks in underfloor heating or underground pipes.
Cost: £200-£400.
Dye Testing
For drain or waste pipe leaks, dye is added to the system and tracked visually. Cheaper and simpler than other methods.
Cost: Often included in standard callout fees (£80-£120).
Emergency Situations
Some leaks need immediate action:
Burst Pipe
Action:
- Turn off the mains water (stopcock usually under the kitchen sink or where the supply enters the property)
- Turn off the boiler and central heating
- Open all taps to drain the system
- Move valuables away from the leak
- Call an emergency plumber immediately
Don’t: Try to fix a burst pipe yourself unless you know what you’re doing. High-pressure water can cause injury.
Ceiling Leak
Action:
- Move furniture and valuables away
- Place buckets to catch drips
- If the ceiling is bulging with water, carefully puncture it with a screwdriver to let water drain (prevents collapse)
- Turn off electricity if the leak is near light fittings
- Call an emergency plumber
Boiler Leaking
Action:
- Turn off the boiler immediately
- Turn off the water supply to the boiler
- Call a Gas Safe registered engineer (don’t attempt to fix it yourself)
Don’t: Ignore a leaking boiler. It can damage the boiler, cause electrical faults, or indicate a serious fault.
Teesside-Specific Issues
Older properties with original pipework: Many Victorian terraces and 1960s estates in Teesside still have original lead or iron pipework. These are prone to corrosion and leaks, especially where pipes pass through walls or floors. If you’re experiencing frequent leaks, consider repiping.
Hard water areas: Teesside has moderately hard water, which can cause limescale buildup in pipes and fittings. Limescale weakens fittings over time, increasing leak risk. A water softener reduces limescale and extends the life of your plumbing.
Cold winters: Frozen pipes are a risk in winter, especially in unheated lofts or external walls. When pipes freeze and thaw, they can burst. Insulate exposed pipes and keep heating on low during freezing weather.
Prevention Tips
Stop leaks before they start:
Service your boiler annually: A plumber checks for leaks, corrosion, and worn seals during a service.
Check visible pipework regularly: Look under sinks, behind toilets, and in the loft every few months.
Insulate pipes: Prevent freezing in winter and reduce condensation in summer.
Replace old fittings: If you have old compression fittings, corroded valves, or worn washers, replace them before they fail.
Monitor your water bill: A sudden increase is often the first sign of a hidden leak.
Maintain heating system pressure: If your boiler pressure drops regularly, investigate before it becomes a bigger problem.
Typical Leak Repair Costs
Rough costs for Teesside in 2026:
Simple tap repair (replace washer): £60-£100
Replace leaking valve (radiator or supply): £100-£180
Fix burst pipe (accessible location): £120-£250
Leak detection service: £150-£300
Underground pipe repair: £500-£1,500 depending on location and access
Boiler leak repair: £150-£400 depending on the fault
Emergency callouts (evenings, weekends) typically add £50-£100 to standard rates.
The Bottom Line
Hidden leaks cause expensive damage if left unchecked. Watch for warning signs (higher bills, damp patches, mould, pressure loss), try simple DIY checks (meter test, visual inspection), and call a professional if you can’t locate or fix the leak yourself.
In an emergency (burst pipe, ceiling leak, boiler leak), turn off the water and call a plumber immediately.
If you suspect a leak in your Middlesbrough, Stockton, or Teesside property, we’re here to help. From simple repairs to advanced leak detection, we’ll find and fix the problem quickly.
Get a free quote or contact us for leak detection and repair.
Related services: Leak Repairs | Emergency Repairs | Plumbing