Plumbing·Leaks

How to find a water leak in your house (2026)

Partially verified Safety-critical topic

Quick Answer

To find a water leak in your house, start by checking whether water is still being used anywhere, then watch your water meter for movement when all taps and appliances are off. Once you know there is a leak, narrow it down by checking common problem points such as toilets, taps, appliance hoses, under sinks, visible pipe joints, the hot water cylinder or boiler area, and damp patches on walls, ceilings or floors. If you cannot isolate the leak, if water is near electrics, or if the leak appears to be inside a wall, under a floor or on the incoming supply pipe, stop and call a qualified plumber or leak detection specialist.

Safety first

If water is near electrical sockets, lighting circuits, appliances or consumer units, keep clear and get qualified help before touching electrics.
Know the location of the main stop valve before you start investigating so you can shut off water quickly if a leak worsens.
Do not cut into walls, floors or ceilings unless you are sure it is safe and you understand what services may be hidden behind them.
Be careful when moving washing machines or dishwashers; avoid straining hoses, damaging flooring or trapping power cables.
Use stable access if checking high areas or ceilings, and stop if the ceiling is sagging or appears waterlogged.
If mould is already extensive or materials are badly water-damaged, seek professional advice on safe clean-up and repairs.

When to call a professional: Stop and contact a qualified plumber or leak detection specialist if the leak is hidden in walls, floors or ceilings; if the meter shows a leak but you cannot isolate the source; if the leak is on or near the incoming supply pipe; if water is near electrics; if the leak involves a boiler, unvented hot water system or major appliance internals; or if there is structural damage, a sagging ceiling, significant mould, or repeated leaks after a DIY repair.

Overview

Finding a water leak is usually a process of confirming that water is escaping somewhere, then isolating which part of the plumbing system is responsible. The most useful first check is your water meter: if it continues to register flow when no water is being used, you likely have a leak on your internal plumbing or the supply pipe. After that, work from the simplest and most common causes first. Toilets are a frequent source because a faulty flapper, flush valve seal or fill valve can let water run continuously into the pan without obvious puddles. Taps, shower valves, washing machine and dishwasher hoses, sink traps and visible pipe joints are other common leak points. Hidden leaks often show up as damp patches, mould growth, peeling paint, warped flooring, stained ceilings, reduced water pressure or the sound of running water when everything is off. Acting quickly matters because even a small leak can damage finishes, encourage mould and increase your water bill. If you find active leaking, the safest first response is usually to shut off the local isolation valve or the main stop valve, then dry the area so you can confirm where fresh water reappears.

Who this is for

Homeowners and tenants who need to check for a suspected internal water leak before deciding whether a simple fix is possible or a plumber is needed.

What you’ll need

torch
dry cloths or paper towels
water meter access if your property has one
notepad or phone camera
food colouring for toilet leak testing if available
basic tools for access panels or appliance connections if needed
main stop valve location identified before you begin

Before you start

Know where your main stop valve is and make sure you can reach it quickly. If there is standing water near sockets, switches, appliances or wiring, do not step into it or touch electrical equipment; isolate power only if it is safe to do so and seek professional help. If you rent, check your tenancy agreement or report the issue to the landlord or managing agent, especially if the leak may be from hidden pipework or a communal supply.

Step-by-step

1
Confirm whether you likely have a leak
Turn off all taps and water-using appliances you control, including the washing machine, dishwasher and any irrigation. Make sure no toilet has just been flushed. Then check your water meter. If the meter continues to show flow or changes over a short period while no water is being used, there is likely a leak somewhere on your side of the supply.
Why: This separates a real leak from normal water use and gives you a clear starting point before opening panels or replacing parts.
2
Check toilets first
Remove the cistern lid and listen for continuous filling or trickling. Put a few drops of food colouring into the cistern and wait without flushing. If colour appears in the toilet pan, water is leaking past the flush seal or valve. Also check whether the fill valve is overfilling and sending water into the overflow route.
Why: Toilet leaks are very common and can waste a lot of water without leaving visible signs on the floor.
3
Inspect visible fittings and appliances
Look under sinks, around basin and bath traps, at tap tails, shut-off valves, shower hoses, radiator valves where relevant, and around washing machine and dishwasher hoses. Run each fitting briefly, then dry every joint with a cloth and check again for fresh moisture. Pay close attention to hose connections and areas where vibration or movement occurs.
Why: Fresh water on a dried joint is one of the easiest ways to identify a slow leak that would otherwise be missed.
4
Look for hidden leak clues in the building
Check ceilings below bathrooms, walls behind showers, skirting boards, flooring edges, cupboards, and areas around the boiler or hot water cylinder for staining, bubbling paint, mould, warped materials, musty smells or unusual warmth. Listen for hissing or running water when the house is quiet and all outlets are off.
Why: Leaks inside walls, floors or ceilings often reveal themselves through secondary damage before the pipe itself is visible.
5
Isolate sections if the source is still unclear
If your plumbing has local isolation valves, shut off one fixture or appliance at a time and recheck the meter. For example, isolate a toilet, then watch the meter; if the movement stops, that branch is likely the problem. If there are no local valves, shut off the main stop valve and note whether the meter still moves. If it does, the issue may be on the supply side before your internal plumbing and needs professional investigation.
Why: Isolation helps narrow the leak to a specific branch or tells you whether the problem is internal or on the incoming pipework.
6
Make the immediate safe fix you are confident about
For a leaking toilet, the fix is often replacement or adjustment of the flush seal, flapper or fill valve according to the manufacturer instructions. For a dripping tap, the cartridge, washer or O-ring may need replacement. For a leaking appliance hose or visible compression connection, shut off the water first, then replace the faulty hose or remake the connection only if you are sure of the correct parts and method. Dry the area and recheck for fresh leaks afterwards.
Why: Simple component failures can often be corrected quickly, but only after the water is safely isolated and the faulty part is positively identified.
7
Stop and escalate if the leak is hidden or causing damage
If the leak appears to be inside a wall, under a floor, from a ceiling void, from the boiler or hot water system, or near electrics, shut off the water supply if practical and contact a qualified plumber. If the leak has affected ceilings, structural timbers or significant finishes, document it with photos for insurance or landlord reporting before repairs proceed.
Why: Hidden leaks and leaks affecting building fabric or electrical safety need specialist diagnosis and repair to prevent further damage.

Why this works

Water leaks can only occur on a section of plumbing that is pressurised or in use. By confirming unwanted flow at the meter, then checking the most failure-prone fixtures and isolating parts of the system, you progressively narrow the fault until the leaking component or pipe run is identified.

Common mistakes to avoid

Assuming a leak is not serious because there is no puddle; many toilet and hidden pipe leaks do not show obvious standing water
Tightening random fittings before identifying the exact leak point, which can damage seals or worsen the leak
Ignoring appliance hoses behind machines, which can leak slowly for a long time
Forgetting to dry joints before checking them again, making it harder to tell where fresh water is appearing
Continuing to use a suspected leaking fixture instead of isolating it first

Troubleshooting

Water meter moves when everything is off, but no visible water is found

Check toilets with dye, then isolate fixtures one by one if possible. If the meter still moves and you cannot find the source, arrange professional leak detection for hidden pipework or the supply pipe.

Damp patch on ceiling below a bathroom

Stop using the shower, bath and nearby fittings, then inspect sealant failure, waste connections and toilet leaks above. If the source is not immediately visible, call a plumber because the leak may be in concealed pipework.

Slow drip under a sink

Dry the trap, tap tails and valves, then run the tap and watch for the exact point of leakage. Replace worn seals, trap washers or flexible connectors only with the correct parts and with the water isolated first.

Toilet keeps refilling or making a faint running sound

Inspect the flush valve seal or flapper and the fill valve level. Replace the faulty cistern component according to the toilet manufacturer's instructions.

Leak appears only when the washing machine or dishwasher runs

Pull the appliance forward carefully, inspect the inlet hose, drain hose and connection points, and replace damaged hoses or seals. If the leak seems to come from inside the appliance, use an appliance engineer or plumber.

Compare your options

DIY visible fixture checks

Best for: Drips, toilet leaks, under-sink leaks and appliance hose issues

Pros: Quick, low cost, often enough to find common leaks

Cons: Will not reliably locate leaks inside walls, floors or buried supply pipes

Meter and isolation testing

Best for: Confirming whether a hidden leak exists and narrowing it to a branch

Pros: Systematic and does not require opening walls straight away

Cons: Needs a water meter and accessible isolation points to be most useful

Professional leak detection

Best for: Hidden leaks, repeated unexplained damp, or leaks under floors or in walls

Pros: More accurate for concealed pipework and can reduce unnecessary damage

Cons: Costs more than basic DIY checks and may still need follow-on repair work

Option	Best for	Pros	Cons
DIY visible fixture checks	Drips, toilet leaks, under-sink leaks and appliance hose issues	Quick, low cost, often enough to find common leaks	Will not reliably locate leaks inside walls, floors or buried supply pipes
Meter and isolation testing	Confirming whether a hidden leak exists and narrowing it to a branch	Systematic and does not require opening walls straight away	Needs a water meter and accessible isolation points to be most useful
Professional leak detection	Hidden leaks, repeated unexplained damp, or leaks under floors or in walls	More accurate for concealed pipework and can reduce unnecessary damage	Costs more than basic DIY checks and may still need follow-on repair work

Alternatives

Ask your water supplier whether they provide guidance on reading your meter or checking for supply pipe leaks
If you do not have a visible meter or cannot access it, start with fixture-by-fixture inspection and toilet dye testing instead

Pro tips

Take photos before dismantling anything so you can reassemble it correctly
Place dry tissue around suspect joints; it often shows a slow leak sooner than a visual check alone
Check after everyone in the home has stopped using water for a while, so normal demand does not confuse the diagnosis
If you find a leak under a sink, also inspect the cabinet base and nearby skirting for older hidden damage

Legal & regulatory notes

Plumbing work, responsibility for supply pipes, and notification requirements can vary by country and tenancy arrangement. If you are a tenant, report leaks promptly to the landlord or managing agent. If the leak may involve shared pipework, a communal system, or regulated plumbing work, check local rules and use an appropriately qualified professional.

What this guide does not cover: This guide covers general household leak finding and simple visible issues only. It does not provide full repair instructions for boilers, unvented cylinders, buried pipes, slab leaks, complex bathroom waterproofing failures, insurance claims handling, or country-specific plumbing code compliance.

Cost considerations

Costs can rise quickly if a hidden leak is left unresolved because water damage, mould growth and replacement of finishes often cost more than the plumbing repair itself. Early diagnosis can also reduce ongoing water charges where metered billing applies.

Prefer to hire a professional?

If this job is beyond a confident DIY — or the work needs to be done by a licensed professional — you can find a verified plumber through Trade Directory (tradedirectory.co.nz), New Zealand's directory of real, verified trade businesses. Compare local tradespeople, read their details and request quotes before you commit.

Find a plumber on Trade Directory

Frequently asked questions

Can I have a water leak if there is no visible puddle?+

Yes. Toilet leaks, hidden pipe leaks, and leaks into walls, floors or ceilings may not create an obvious puddle. Your meter, damp staining, mould, warped materials or the sound of running water can be the first signs.

What is the most common hidden leak in a house?+

A leaking toilet is one of the most common because water can pass silently from the cistern into the pan. Appliance hoses and small leaks at under-sink joints are also common.

Should I turn off the main water supply straight away?+

Turn it off if water is actively escaping, if you cannot control the leak locally, or if the leak is causing damage. If the issue is only suspected and not urgent, you can often diagnose first, but be ready to shut the water off if the situation changes.

How do I know if the leak is on the incoming supply pipe?+

If your meter indicates flow when your internal stop valve or all internal fixtures are isolated, the leak may be on the supply side before the house plumbing. That usually needs your water supplier's guidance and a qualified plumber or leak detection specialist.

Can I repair a leaking pipe joint myself?+

Only if the leak is fully visible, you can isolate the water safely, and you know the correct replacement part and method. Hidden pipework, repeated leaks, and any leak near electrics are better handled by a professional.

Sources & references

Guidance on this page is traced to documented sources. Last checked 24 September 2026.

EPA WaterSense - Fix a Leak Week · government
Supports that household leaks are common, toilets are a frequent leak source, and checking and fixing leaks promptly matters.

The basic process for finding household water leaks changes slowly, although local plumbing rules and repair responsibilities can vary.