How to replace a leaking flexi hose under a sink

🔧 Replacing a Leaking Flexi Hose Under a Sink — Professional Trade Guide

Plumbing work in Australia must be performed by a licensed plumber. This guide explains the process and helps you select the right tools and materials.

What is involved in replacing a leaking flexi hose under a sink?

Replacing a leaking flexi hose under a sink is a routine but high-priority maintenance task, particularly where braided connector failures, weeping crimp collars, split liners, or deteriorated sealing washers are causing active leakage. The correct repair involves isolating the supply, confirming thread compatibility and pressure rating, replacing the connector with a compliant flexible hose, and testing in accordance with the PCA and AS/NZS 3500 requirements.

For Australian installations, use only compliant flexible connectors suitable for potable water, with correct end configurations and pressure/temperature ratings for the application. Flexi hoses are not to be twisted, kinked, overstressed, or used outside manufacturer bend radius limits.

What skill level is required to replace a flexi hose?

Intermediate — Estimated time: 0.5–1.5 hours

What tools are essential for replacing a flexi hose?

What materials are needed for a flexi hose replacement?

Safety Requirements

Step-by-Step Guide

Step 1: Assess the leak source

Identify the exact failure point before removing anything. Common leak points include the crimped ferrule at the braided hose end, the captive nut connection at the stop valve, the tap tail connection, a split inner liner, or seepage from a faulty mini stop.

Wipe the area dry and pressurise briefly if needed to confirm the source. Check whether the leak is from:

If the hose has ballooned, kinked, corroded, or shows braid distortion, replace it immediately rather than attempting to reseal.

Step 2: Isolate the water supply

Shut off the local under-sink mini stop or angle stop valve where fitted. If the valve does not fully isolate or begins leaking at the spindle, isolate at the property main.

Open the mixer or tap to relieve pressure and drain residual water. Place a bucket and rags under the work area before loosening any connection.

💡 If the local valve is unserviceable, this is often the right time to replace it with a compliant 15 mm quarter-turn mini stop for future maintenance access.

Step 3: Confirm hose specification and connection type

Before removal, identify:

Most under-sink connectors are 1/2" BSP at the valve side, but tap-side configurations vary widely, including fixed female swivel ends or mixer-tail thread connections such as M10 or M12.

Measure the installed hose along its natural run, not stretched tight. Select a replacement long enough to form a gentle curve with no tension. Avoid excessive slack that may cause rubbing or trapping.

Step 4: Remove the leaking flexi hose

Use one spanner to support the valve or tap tail and a second to loosen the swivel nut. This prevents torsional loading on copper tube, mini stops, or mixer bodies.

Disconnect the hose carefully and inspect both mating faces. Remove any old washer fragments, debris, scale, thread sealant contamination, or damage at the sealing face.

If the stop valve outlet is loose in the wall or mounted on unsupported tube, stabilise it before proceeding. Do not allow branch pipework to twist.

Step 5: Inspect associated components

Check the condition of:

Where one hose has failed due to age, the matching hose may be near end-of-life as well. On trade maintenance work, it is often prudent to replace both hot and cold braided connectors if they are of similar age and condition.

Also check static pressure if there is evidence of repeated hose failures. Excessive pressure may require a pressure limiting valve under AS/NZS 3500 conditions.

Step 6: Install the new flexi hose

Fit the replacement hose by hand first to avoid cross-threading. Ensure any captive washer is correctly seated. Tighten to manufacturer specification; where no torque data is supplied, tighten firmly without over-compressing the washer or damaging the swivel nut.

Important installation rules:

Where connecting to a mixer tail first, secure that end and then connect the valve end while keeping the hose in a natural relaxed curve.

💡 A properly installed braided hose should sit in a smooth loop, not a corkscrew.

Step 7: Reinstate supply and pressure test

Close the tap outlet, then slowly reopen the isolation valve or main supply to avoid hydraulic shock. Pressurise the hose gradually.

Inspect all joints with a torch and dry tissue or rag. Run both hot and cold water for several minutes, then recheck under static and flowing conditions.

Look for:

If a joint weeps, isolate again and rectify the sealing issue. Do not continue tightening blindly.

Step 8: Final compliance and service checks

Confirm the hose is accessible for future maintenance and not concealed in a manner contrary to good service practice. Ensure there is no mechanical strain on the connection and that the valve remains operable.

Where relevant, check delivered water temperature requirements, especially if the under-sink outlet is connected to tempered hot water serving sanitary fixtures. If this work formed part of broader maintenance, document product details and date of replacement for future asset records.

💡 For rental or strata maintenance, noting the brand, hose length, and install date helps reduce repeat emergency call-outs.

Common Mistakes to Avoid

Pro Tips

Recommended Tools

⚠️ Safety

🔒 Licensing

Plumbing work in Australia must be performed by a licensed plumber. This guide explains the process and helps you select the right tools and materials. State licensing oversight includes NSW Fair Trading, VIC VBA, QLD QBCC, and WA Building Commission.