Bathroom, kitchen & fixture leak detection in Brisbane, CA
A drip under the sink, a toilet that refills by itself, or a cabinet floor that’s always damp: fixture leaks are often small, but they’re easy to misread. A fixture investigation typically examines the affected fixture, its accessible supply and drain connections, and the timing of the moisture to narrow the likely source. Brisbane Leakmark takes fixture leak inquiries for properties in Brisbane and the nearby communities shown on our service areas page.
Tell us which fixture is acting up. Name the room and when the water shows up.
Call (415) 532-1415Which fixture leaks can be investigated?
A fixture leak is water escaping at or near a point of use. That includes the fixture itself, the shutoff valve feeding it, the supply tube or hose, and the drain connections underneath.
It does not include a pipe failing deep inside a wall, under a slab or underground. Those leaks need a different investigation—see hidden water leak detection when the source seems to be inside the structure rather than at a fixture.
Why does a fixture leak only when it is used?
When water shows up is one of the best clues.
| Pattern | What it suggests | Typical places |
|---|---|---|
| Wet all the time, even overnight | Pressurized supply side: valve, supply tube, fixture inlet | Angle stops, faucet supply tubes, toilet fill valve connection |
| Wet only after a fixture runs | Drain side, or a seal that only gets water during use | Sink traps, tub overflow, shower pan, toilet wax ring |
| Wet only during heavy use | Splash, failed caulk or grout, overflow | Shower doors, tub edges, sink rims |
| Meter moves, but nothing looks wet | Water going down a drain or out of sight | Toilet tank-to-bowl leak, a pipe in a wall |
Can a toilet leak without making noise?
Toilets can leak without a sound and without any water on the floor. Water slips past a worn flapper from the tank into the bowl and straight down the drain. EPA WaterSense notes that worn toilet flappers can cause substantial silent water loss.
How to run a dye test
- Lift the tank lid and set it somewhere safe. Lids are heavy and break easily.
- Add a few drops of food coloring to the tank water. Don’t flush.
- Wait about 10 minutes without using that toilet.
- Check the bowl. Any color there means water is leaking from the tank.
- Flush afterward so the dye doesn’t stain the tank.
Also listen for the fill valve turning on by itself between flushes—another sign the tank is losing water.
Is water under a sink coming from the supply or drain?
A sink has two separate water systems. Each leaks differently.
Supply side
The hot and cold shutoff valves, the supply tubes and the faucet body. This side may remain under pressure when the faucet is off, so a leak can continue without fixture use.
Drain side
The basket strainer, tailpiece, P-trap and wall connection. Drain-side leakage commonly appears during or after use, and residual water may continue dripping afterward.
If electrically safe with no active flooding, gently dry accessible surfaces and observe whether water reappears with the faucet off, then during normal use. Seepage from hidden or previously wet areas can blur the pattern.
Shower and tub: trim, seals and plumbing
Shower leaks are hard to place because many parts sit behind tile.
| Possible source | Shows up as | When it leaks | Check first |
|---|---|---|---|
| Showerhead or arm connection | Drips from the head, staining above it | During and after use | Visible drips with the valve off |
| Valve cartridge or body | Constant drip, wet wall on the far side | All the time if supply-side | Water while the shower is off |
| Trim, caulk or grout | Water outside the enclosure | Only during showers | Wet floor beside the tub or pan |
| Drain or overflow gasket | Ceiling stain below the tub | Only when draining | Stain grows after baths |
| Shower pan | Damp subfloor, stain below | During long showers | Moisture near the base |
Kitchen cabinets and disposals
Kitchen sink leaks often show up in this order:
- Swelling or soft spots in the cabinet floor
- A musty smell when the door opens
- Water rings on stored items
- Drips you can see from the disposal, drain or supply tubes
Do not operate the disposal or another electrical appliance where water has reached wiring, an outlet or the device housing.
Dishwashers, ice makers and supply hoses
Appliances connect to the plumbing through small supply lines. Those connections are part of fixture leak detection:
- Dishwasher supply line and drain hose connection
- Refrigerator ice maker and water dispenser line
- Washing machine hot and cold supply hoses
- Each appliance’s shutoff valve
This looks at where the water connects. It does not cover appliance repair.
Water heaters: supply connection versus tank
Water near a water heater may come from a supply connection, a relief valve discharge line or the tank itself. Fixture leak detection can check the plumbing connections. Work on the tank, burner, element or relief valve itself is outside this service unless a separate service is specifically agreed.
If water is near a heater’s gas or electrical components, keep clear of hazardous equipment and call a qualified professional. Operate a water shutoff only if it is safely accessible; never attempt to bypass a relief valve or alter gas/electrical controls.
How to tell fixture leaks from slab problems
A fixture problem and a slab or in-wall leak can both raise a water bill. This quick triage helps separate them.
| Clue | Points to a fixture | Points to a slab or in-wall pipe |
|---|---|---|
| Location | Wetness at a cabinet, toilet base or tub | Damp floor away from fixtures, warm floor area |
| Fixture valve closed | Leak stops | Leak continues |
| Dye test | Toilet shows color | All toilets pass |
| Meter with all fixtures off | Meter stops after a fixture is isolated | Meter keeps moving |
If meter movement continues after safely isolating accessible fixtures, see hidden water leak detection.
Safe homeowner checks before you call
- Dry each fixture area and check it again after an hour
- Run a dye test on every toilet
- Look for drips at angle stops and supply tubes with the faucets off
- Check appliance hoses for bulges, cracks or wet fittings
- Find each fixture shutoff valve, and turn it gently. Don’t force a stuck valve
- Note when the water appears: always, during use, or after draining
Meter checks when no faucet runs
If every fixture is off and the meter’s low-flow indicator still moves, water is leaving the system somewhere. EPA WaterSense suggests reading the meter, using no water for two hours, then reading it again. Close one fixture valve at a time and watch whether the indicator stops. For step-by-step help, see how to check a water meter for leaks.
Controlled use-testing and dye testing
A technician narrows a fixture leak by turning one variable on at a time:
- Baseline: Dry the area and confirm the meter reading with everything off.
- Supply hold: Open the fixture’s supply valve and watch for drips without using the fixture.
- Use test: Run the fixture for a set time, then check the drain connections.
- Drain test: Fill and release the sink or tub to load the drain and overflow.
- Dye trace: Where water paths are hidden, colored water can show which route reaches a stain.
Do not deliberately run additional water through a fixture if doing so could worsen flooding, saturate damaged finishes or create an electrical hazard.
Moisture tracing near cabinets and wall cavities
Moisture meters can show which part of a cabinet floor or wall is wetter than the rest. They can’t tell you whether that moisture came from a supply tube, a drain or a splash. If moisture extends into the wall cavity, the leak may be behind the fixture. Small access openings may be needed to confirm it.
Testing the drain side versus the pressurized supply side
| Test result | Supply side | Drain side |
|---|---|---|
| Wet with fixture off and valve open | Yes | — |
| Dry until fixture drains | — | Yes |
| Leak stops when the fixture valve closes | Yes | — |
| Stain grows after a bath or full sink | — | Yes |
| Meter moves with all fixtures off | Yes | — |
How inspection differs from repair
1. Inspection
Confirms which fixture, connection or drain part is leaking.
2. Findings
Are explained, including anything that couldn’t be confirmed.
3. Repair
Is a separate step. It may happen on the same visit for simple parts, or later for parts behind tile or walls.
Ask which component-level repairs, if any, are available. See fixture and supply line leak repair for that side of the work.
Potential component-level repair options
Depending on what the inspection finds, and only where repair capability is confirmed:
- Replacing a toilet flapper, fill valve or wax ring
- Replacing a supply tube or angle stop
- Tightening or resealing a drain connection
- Replacing a shower valve cartridge
- Recaulking where water escapes the enclosure
None should be quoted before the source is confirmed.
When repeated small leaks need broader assessment
- Several supply tubes or valves leaking within a short period
- Corrosion or mineral crust on many connections
- Leaks returning soon after the same part was replaced
- Water pressure that seems unusually high at fixtures
That pattern may justify a broader plumbing check instead of one-part fixes.
Pre-visit access and photos
- Clear out the cabinets under affected sinks
- Make the access panels behind tubs or showers reachable, if you have them
- Photograph stains, wet spots and any damaged cabinet floors
- Note the fixture brand or model if it’s visible
- Make sure pets and stored items are clear of the work area
Brisbane water-use context
For a fixture-by-fixture walkthrough, consult the City of Brisbane water conservation resources, including its Residential Self-Audit Tool. If a fixture leak has shown up on your bill, see why is my Brisbane water bill high? For stains that may come from a sewer line or the roof, see plumbing leak vs sewer vs roof moisture.
Fixture leak detection FAQs
Can a toilet leak without making noise?
Yes. Water can seep from the tank into the bowl past a worn flapper without any sound or water on the floor. The bowl looks normal and the fill valve may only turn on occasionally. A dye test or a meter check is the most reliable way to catch it.
How do I check a toilet with food coloring?
Add a few drops of food coloring to the tank, not the bowl, and don’t flush. Wait about 10 minutes. If color reaches the bowl without flushing, water is crossing from tank to bowl. Flush afterward to prevent staining. Repeat the test on every toilet in the home.
Why does water appear only after using the shower?
Moisture that appears after use can point toward components that carry or receive water during use: the drain, the overflow, the shower pan, caulk or grout lines, or a showerhead connection. A supply-side valve leak may continue between uses while the valve remains pressurized.
Is a wet cabinet always a supply-line leak?
No. Water can come from supply fittings, the faucet, drain trap, disposal, dishwasher connections or splashing. Where safe, observe whether moisture returns with the faucet off or only during normal use.
Can an appliance hose cause a high water bill?
A leaking supply hose or fitting on a dishwasher, ice maker or washing machine can waste water, especially if it drips all the time. Often the leak is visible as moisture behind or under the appliance.
Does this service repair dishwashers or water heaters?
No. Fixture leak detection covers the plumbing connections that feed and drain appliances. It does not repair the appliance itself or service a water heater’s tank, burner or controls.
How do you distinguish a fixture drain leak from a pressure leak?
Supply leaks may continue with the valve open even when a fixture is off. Drain leaks often track fixture use, although trapped water may remain afterward. Concealed leaks sometimes still require access.
When should I shut off the fixture valve?
Shut it off when you see an active drip or spray at a supply tube or valve, a toilet that won’t stop running, or water spreading onto floors or cabinets. If it’s stuck or leaks when turned, use the main shutoff instead and call for help.
Call about a leaking fixture or connection
Whether it’s a toilet that won’t stop refilling, a cabinet that stays damp, or a stain below a shower, describe what you’re seeing and which room it’s in.
Call (415) 532-1415