You open the cupboard for a dishwasher tablet and find a puddle beneath the filter. Perhaps you changed the cartridge yesterday, or had a new filter connected to older kitchen plumbing. The canister is wet, so it's tempting to grab a spanner and tighten it.
Don't assume the wettest part is the failed part. Water can travel down a hose, collect around the filter head and drip from a perfectly sound housing. With an under sink water filter leaking, the first job is to identify the source, especially if a braided connector is involved.
Find the Joint That Is Actually Wet
Find the first fresh bead, not the lowest drip. Photograph the wet joint and surrounding damage before wiping the cabinet, provided you can do so safely. If water is spraying, pooling rapidly or approaching electrical equipment, isolate the supply rather than running a diagnostic test.
The connector deserves as much attention as the cartridge. CHOICE's guide to insurance for burst pipes and water leaks reports Suncorp's finding that escape-of-liquid incidents represent 14% of its Australian home-insurance claims. A small filter installation can add joints or put strain on an existing hose, so inspect the whole connection.
Trace fresh water with dry tissue
For a contained seep with no damaged components, close the local isolation valve and shut the filtered-water tap. Dry the plumbing, then open the isolation valve slowly while keeping your hand within reach of it. Don't loosen anything during this test.
Press a fresh tissue against each point separately, working from the supply towards the tap:
- Isolation valve: Check around the spindle behind the handle and the outlet nut.
- Braided connector: Touch both end nuts and the ferrules where the braid meets the ends.
- Filter assembly: Check the head inlet, cartridge connection and housing-bowl seam.
- Outlet tubing: Test around the push-fit collet, the small ring where the tube enters.
- Filtered tap: Reach beneath the bench to check the tap shank and tube connection.
Watch for several minutes, then repeat while the filtered tap runs and immediately after it stops. Use the table to match the first wet tissue to a safe response.
Where an under-sink filter leak shows and what to do first
| Location | What you see | Safe first action | Stop and call a plumber if |
|---|---|---|---|
| Cartridge O-ring or housing bowl | Drip at the seam after a change, sometimes during flow | Isolate, fit a matching lubricated O-ring and refit without force | Threads are cracked, cross-threaded, or the bowl still weeps |
| Filter head inlet | Bead at the inlet with the bowl dry | Identify the seal type; renew a face-sealing washer where fitted | Head is split or still weeps with the correct seal |
| Push-fit or John Guest | Weep at the collet, or tube creeping outward | Isolate, cut sound tube square, deburr, insert fully and pull-check | Tube is scratched or oval, or the collet is cracked |
| Isolation valve | Drip from spindle or outlet nut | Isolate upstream and arrange valve assessment; don't turn unfamiliar nuts | Valve won't shut or the body is corroded |
| Braided flexi-hose | Spray, bulge, ferrule corrosion, or wet nut with dry filter | Shut the water and arrange replacement, not straightening | Braid is broken, hose bulges, or it's kinked against cabinetry |
| Filtered tap shank | Drip beneath the bench at the tap tail | Isolate and identify the washer or connection needing attention | Shank is loose in stone or the thread is stripped |
Read the clues without guessing
A bead appearing when flow starts can indicate a tube under sideways tension or a tired seal, but timing alone doesn't identify the fault. Spray above a dry filter head points towards the hose or valve; a swollen kickboard without a fresh drip suggests previous or intermittent wetting.
Use a torch rather than judging stains under warm cabinet lighting. If you're comparing the dried finish with surrounding cabinetry, SouthRay Kitchen & Bath's guide to how lighting affects kitchen colors provides useful context, but swelling and moisture are stronger evidence than colour alone.
How to Stop the Drip and Reseal It
Once you've identified the joint, choose the repair for that connection. These instructions suit accessible routine maintenance, not cracked pressure components, concealed pipework or unfamiliar boiling-water equipment.
This overview shows the isolation, repair and testing sequence. Snugging a fitting is appropriate only when that fitting is designed for adjustment.
Isolate before opening the system
Protect the cabinet. Put a bucket and towels beneath the filter, and remove cleaning bottles and storage trays. You need an unobstructed view of the floor and enough clearance to remove the bowl straight down.
Close the local isolation valve. If it won't stop the supply, close the property mains and open a suitable cold tap to release supply pressure. Don't force a seized handle or start dismantling while water continues feeding the leak.
Relieve trapped filter pressure. Open the filtered-water tap and let the flow stop. Switch off and unplug an associated chiller only if the plug and surrounding area are dry; keep clear of wet electrical equipment and seek professional help instead. A reverse-osmosis tank may need separate isolation according to its service instructions.
Repair only the connection that failed
For a cartridge or bowl seam, inspect the seal. Remove the bowl, discard a flattened, swollen or nicked O-ring, and wipe its groove clean. Lightly coat the exact replacement with compatible food-grade silicone lubricant, seat it without twisting, and confirm the cartridge is correctly positioned. Start the bowl threads by hand; use only the final tightening movement specified for that housing, not extra force to overcome resistance.
For a push-fit, prepare the tube properly. With pressure released, remove any retaining clip, depress the collet and withdraw the tube. Recut an intact, round section with a tube cutter, remove burrs without scratching the sealing surface, and push it fully to the internal stop. Make a controlled pull check and refit the clip where supplied; leave the tube entering straight rather than bent against the fitting.
For a washer-sealed inlet, renew the washer. Check that the mating faces are clean and the replacement fits properly. PTFE tape won't repair a face seal and mustn't be used on a push-fit tube seal. Stop if the plastic thread binds, distorts or shows a split.
A demonstration can help you recognise the components, but match the service method to your own filter.
Prove the repair under pressure
- Restore pressure slowly and test. Wipe each connection dry, inspect for several minutes, operate the filtered tap and inspect again after shutting it. Assess adjacent connections too, because moving a housing can disturb its tubing.
Australian cold-water repairs sit within the scope of AS/NZS 3500.1:2021, which covers design, installation, commissioning, alteration and repair. The complete water-service connection matters, including applicable backflow controls; use a licensed plumber for plumbing alterations and work beyond permitted routine maintenance.
- Finish with a dry-paper test. Once the attended pressure test passes, leave a fresh paper towel beneath the assembly overnight and check it in the morning. The pass condition is a dry towel, no bead at any tissue-test point and a valve that fully shuts. Any fresh moisture means the repair hasn't passed; isolate it rather than leaving it running.
When the Flexi-Hose Is the Real Risk
A slow housing weep can damage a shelf. A failed pressurised braided connector can release water into the room, whether or not anyone opens the filtered tap. That's why a dry cartridge doesn't make the installation safe.
The braid isn't the water seal. It supports the flexible inner hose, while the connector ends hold the assembly together under pressure. Broken strands, a distorted end or a kink are reasons to question the assembly, not cosmetic faults to tidy up.
Use the inspection points below to look beyond the filter canister.
Look at the ends and the route
Follow the hose without pulling or bending it. Look for broken braid, bulging, green or white deposits at the ferrules, and rub marks where it touches cabinetry. A spiralled or twisted appearance near a nut can indicate that the hose turned during tightening rather than remaining supported.
A newly added filter can create these problems without immediately leaking. Say the filter head hangs partly from the connector, or an existing hose is stretched to reach a new manifold. Each cartridge change then moves a pressure connection that should have remained supported.
A sharp turn into a John Guest stem can also pull sideways on the adjoining fitting. Correct routing means a relaxed curve within the manufacturer's minimum bend radius, with no tension at either end.
Replacement rule: A kinked hose that isn't leaking today still needs attention before you leave the house unattended. Straightening it doesn't establish that its internal structure is sound.
Choose a pressure component, not a patch
The WaterMark WMTS-520 specification covers accessible, above-ground semi-flexible metallic hose assemblies and defines failure as leakage, permanent deformation or a local radius reduction exceeding 50%. In household terms, a visibly deformed hose shouldn't be returned to service just because the drip stopped.
A replacement must match the connection diameter, thread, washer arrangement, and pressure and temperature ratings. Select a WaterMark-certified assembly suitable for the application, support it independently of the filter head, and leave both ends accessible for inspection.
Don't put an external clamp over a failed braided pressure connector. If you're trying to distinguish a clamp-secured hose from a threaded assembly, this guide to a flexible hose clamp can help clarify the connection type; it isn't a substitute for replacing a damaged pressure hose.
The installation should remain inspectable after the cleaning caddy goes back. A hose hidden behind a full cupboard is harder to check and easier to knock into a strained position.
Stop a Slow Leak Becoming a Claim Problem
A drip under the sink can look harmless while water tracks into cabinet panels, the kickboard or flooring. A container only catches water until it fills, shifts or gets forgotten. The higher-consequence leak may be a filter-added joint or braided hose, not the cartridge. Isolate the supply or arrange a repair rather than relying on a bowl.
Yarra Valley Water's leak guidance notes that unnoticed leaks can add noticeably to household water use, and that early detection limits both waste and damage.
A hidden drip isn't automatically covered
Insurers may treat a sudden accidental escape of liquid differently from gradual leakage. A connector that fails and is discovered promptly is not the same situation as a cabinet that has stayed damp while someone repeatedly empties a bowl.
Coverage depends on the policy wording, the cause, maintenance history and when the damage became apparent. A photograph records what you found, but it cannot establish when all the damage occurred. Before a holiday, check your policy's unoccupancy and maintenance conditions rather than assuming an empty Melbourne home has unchanged cover.
Monitoring a drip is not a repair. Once you know it's there, stop the water or arrange the work.
Use a trigger-based cabinet routine
Check the cabinet after a cartridge change, before leaving for a holiday, or if you notice a musty smell or swollen kickboard.
- Prove the shut-off works: Confirm the local valve stops the filter supply, rather than merely reducing the flow.
- Check hoses: Look for broken braid, deformation or routing that forces a tight bend. Arrange replacement if you find damage.
- Inspect surrounding materials: Check the cabinet floor, lower panel edges and kickboard for swelling or soft spots.
- Use the meter carefully: Note the reading before a weekend away and when you return. Account for irrigation, appliances and anyone using the property. A check during a period with no water use can help isolate unexplained consumption.
- Plan for vacancy: Follow the system's shutdown instructions to isolate the filter where appropriate. Arrange help if you can't identify its supply.
- Keep a dated record: Save a photograph of the wet joint, the discovery date, shut-off time and repair paperwork.
A smart water meter may help flag unexpected consumption, but someone still needs to respond. If cabinetry or flooring needs repair, keep records that distinguish the plumbing fault from the resulting damage. Guidance on documenting scopes for insurance repairs can help describe the work clearly without assuming what an insurer will accept.
Fix or isolate the leak today. Use the cabinet routine before your next trip so an unresolved drip doesn't go unchecked.
Decide DIY, Plumber, or Isolate Today
Stop if you can't control the supply. A seized valve, water emerging from the wall, a cracked filter head or several fittings weeping together calls for professional assessment. Don't keep replacing individual seals when you haven't established why the assembly is failing.
Treat an unfamiliar backflow device or a shared boiling-and-chilled-water installation as another stop point. These systems can include stored pressure, electrical equipment and hot water, so a simple-looking tube may not be an ordinary cold-filter connection.
Separate routine maintenance from plumbing work
A homeowner's reasonable starting point is an accessible cartridge seal covered by the product's maintenance instructions. Having the tools to undo a supply connection doesn't establish that replacing it is permitted or appropriate. For Melbourne water-service repairs, use a licensed plumber rather than treating this table as permission to alter plumbing.
DIY or a plumber for each under-sink leak
| Job | Do it yourself when | Call a plumber when | Parts to have ready |
|---|---|---|---|
| Reseat the cartridge seal | Valve shuts, housing threads are clean, and the manual permits owner maintenance | Bowl is cracked or won't seal with a new O-ring | Matching O-ring and compatible food-grade silicone lubricant |
| Recut a push-fit tube | It's a permitted service task, tube is round, and collet is intact | Several fittings leak, tube is scored, or supply plumbing needs alteration | Correctly sized tube or matching push-fit, plus square tube cutter |
| Replace an inlet washer | It's an expressly permitted maintenance connection with matching, undamaged threads | Head is split, plastic is distorted, or adaptor doesn't match | Correct fibre or rubber washer |
| Swap a flexi-hose | Only where owner replacement is permitted and expressly covered by the equipment instructions | It's a fixed water-service connection, isolation fails, or the line is heated or concealed | WaterMark hose with matching thread, seal and rating |
| Valve or wall connection | Not a DIY job | Valve is seized, leak is at the wall, or backflow is involved | Plumber-selected isolation valve and adaptor |
Don't make access worse to finish a repair. If removing the bowl requires bending the supply hose or forcing the head against the cabinet, the installation needs attention before another cartridge change.
A working valve is also a service-access requirement, not just an emergency convenience. Use the shut-off valve guide to help identify the component before discussing replacement with your plumber.
Assemble the parts before dismantling
For permitted maintenance, set out a torch, fresh tissues, bucket, towels, adjustable spanner, tube cutter and deburring tool. Add the correct housing wrench if your filter uses one. Keep tools off the clean cartridge and sealing surfaces.
Match replacement parts to the filter head, not to a photograph of something similar. Useful identification includes the model label, tubing markings, connector markings and a clear picture of the assembled joint.
- O-rings and washers: Use the specified size and material. A generic ring that looks close can pinch, swell or fail to sit correctly in the groove.
- Tubing and push-fits: Don't mix inch and metric tube. Similar-looking outside diameters aren't proof of compatibility.
- Threaded fittings: Confirm both the thread and sealing method before choosing a John Guest or brass replacement.
- Flexible assemblies: Check the end connections as well as the hose rating. A nut that starts turning isn't proof that the connection matches.
Ring Hot Water is one option for Melbourne installation, repairs and filter maintenance, with genuine valves, hoses and fittings available for delivery Australia-wide. A licensed local plumber or the equipment manufacturer's authorised service agent may also be appropriate, particularly for integrated systems.
Choose a same-day outcome
A serviceable standalone filter: If the valve holds and the fault is within permitted owner maintenance, obtain the matching part before reopening the assembly. Complete the controlled refill and inspection rather than assuming that successful reassembly means a successful repair.
A rental or workplace kitchen: Save the photograph and shut-off time, then notify the property or facilities manager. Leave a clear note identifying what's isolated so someone else doesn't restore the supply without understanding the fault.
A boiling or chilled system: Leave the affected equipment safely isolated until a technician familiar with that brand attends. Don't disconnect an unidentified line because it resembles the tubing on a basic filter.
When booking, name the joint that failed the tissue test, say whether the isolation valve holds, and describe any hose corrosion, kinking or electrical exposure. Those details help the technician bring compatible parts and distinguish a seal service from a wider installation repair.
Ring Hot Water offers under-sink filter installation, leak repairs and maintenance across metropolitan Melbourne, plus genuine replacement parts delivered Australia-wide. Visit Ring Hot Water with your filter model and a photograph of the leaking connection to arrange service or get help matching the correct part.
