How do i fix a leaking flexi hose under the sink? (2026)
Quick Answer
To fix a leaking flexi hose under a sink, first turn off the isolation valve or main water supply, dry everything, and find exactly where the leak is coming from. If the leak is at a threaded connection, you may be able to stop it by gently tightening or reseating the hose; if the hose body is split, bulging, corroded or leaking from a crimped end, replace the hose rather than trying to patch it.
Overview
A leaking flexi hose under a sink is usually caused by one of three things: a loose connection, a damaged sealing washer or O-ring, or a hose that has reached the end of its life. The right fix depends on where the water is escaping. A slow drip from the nut at the tap or shut-off valve may be fixable by isolating the water, undoing the connection, checking the seal, then refitting the hose correctly. But if the braided outer cover is damaged, the inner hose has split, or water is coming from the crimped metal end, replacement is the safe option. Temporary patching is not reliable for a pressurised supply hose. Work methodically: dry the area fully, use tissue or kitchen roll to pinpoint the leak, and only turn the water back on briefly to test. Avoid overtightening, which can distort seals or damage threads. Also check whether the leak is really from the flexi hose and not from the tap body, waste pipe or sink edge above. If you cannot isolate the supply, if fittings are badly corroded or seized, or if you are unsure about matching replacement parts, it is safer to call a plumber. Water supply leaks can quickly cause cabinet damage, mould and larger failures if left unresolved.
Who this is for
Homeowners or tenants dealing with a visible leak from the water supply flexi hose beneath a kitchen or bathroom sink, where the shut-off can be safely isolated.
What you’ll need
- Adjustable spanner or the correct-size spanners
- Bucket or washing-up bowl
- Old towels or cloths
- Kitchen roll or tissue to trace the leak
- Torch
- Replacement flexi hose if the old one is damaged
- Replacement washer or seal if the hose design uses one
- Manufacturer instructions for the hose or tap if available
Before you start
Check whether there is an isolation valve under the sink and make sure it actually shuts the water off before undoing anything. Identify whether the leak is from the supply hose, the tap tail connection, the shut-off valve, or a drain/waste pipe, because the fix is different. If the hose supplies hot water, let nearby pipework cool if it has been recently used. If the cabinet contains electrical items such as a disposal unit, water filter power supply or socket, switch power off to that area before working.
Step-by-step
- 1
Shut off the water and protect the area
Turn off the under-sink isolation valve for the leaking line. If there is no working isolation valve, turn off the main water supply. Open the tap to relieve pressure and confirm the water is off. Put a bucket and towels under the hose.
Why: This prevents more water escaping when you loosen the connection and reduces the chance of a sudden spray.
- 2
Find the exact leak point
Dry the hose, fittings and surrounding pipes thoroughly. Then briefly turn the water back on and watch closely with a torch. Use dry tissue around the top nut, bottom nut, hose body and crimped ends to see where moisture first appears. Turn the water off again before making repairs.
Why: A leak can travel along the braid or fitting, so the visible drip point is not always the true source.
- 3
Try a gentle tighten if the leak is at a threaded joint
If water is coming from the connection nut rather than the hose body, hold the fixed part with one spanner if needed and gently tighten the hose nut with another. Do not force it. Turn the water back on and test again.
Why: A connection may simply have loosened slightly, but excessive force can strip threads, crack fittings or crush the seal.
- 4
Disconnect and inspect the hose if tightening does not stop it
With the water off again, undo the leaking connection and inspect the threads, sealing face and any washer or O-ring. Look for splits, flattening, twisting, dirt or limescale on the seal. Clean the mating surfaces and replace any worn seal with the correct type for that hose.
Why: A damaged or displaced seal will keep leaking even if the nut feels tight.
- 5
Replace the hose if the hose body or crimp is leaking
If the braid is frayed, the hose is kinked, bulging, corroded, or leaking from the hose itself or the crimped metal end, remove it and fit a like-for-like replacement that matches the tap and valve connections and is suitable for the water service. Route the new hose without twists, sharp bends or strain.
Why: A failed hose cannot be reliably repaired in place, and stress on the new hose can cause another leak.
- 6
Refit carefully and avoid cross-threading
Start threaded connections by hand so they screw on smoothly. If the fitting does not turn easily by hand, back it off and realign it. Once hand-tight, use a spanner to snug it up only as much as needed to seal, following any manufacturer guidance that came with the hose or tap.
Why: Cross-threaded or overtightened fittings often leak and may permanently damage the valve or tap tail.
- 7
Turn the water back on slowly and test
Open the isolation valve or main supply slowly. Watch the connection while pressure returns, then run the tap and check again with tissue. Recheck after a short while and again later for any slow seepage.
Why: Some leaks only appear once the hose is fully pressurised or after movement from using the tap.
Why this works
Flexi hose leaks are normally caused either by failure of the seal at the connection or failure of the hose assembly itself. Reseating or replacing the seal fixes connection leaks; replacing the whole hose fixes structural failure. Careful routing and correct tightening prevent stress and damage that can create future leaks.
Common mistakes to avoid
- Trying to patch a split or leaking crimp on a pressurised hose with tape, sealant or glue
- Overtightening the nut and crushing the washer or damaging the thread
- Using thread tape where the fitting seals with a washer or flat-faced seal rather than the thread itself
- Replacing the hose with the wrong end fittings or an unsuitable type
- Leaving the hose twisted or sharply bent after installation
- Assuming the flexi hose is leaking when the water is actually running down from the tap base or another fitting above
Troubleshooting
The joint still drips after tightening
Turn the water off, disconnect the joint, inspect the washer or O-ring, clean the mating surfaces, and refit or replace the seal. If the fitting or thread is damaged, replace the hose or the mating valve/tap part as needed.
Water appears on the braid but the connection looks dry
Check for a pinhole or split in the inner hose, or leakage from the crimped end that is wicking along the braid. Replace the hose.
The nut will not thread on cleanly
Do not force it. Remove it, inspect for cross-threading or mismatched fittings, and confirm the replacement hose is compatible with both ends.
The isolation valve will not fully shut off
Turn off the main water supply instead. If the valve itself is leaking or seized, arrange for repair or replacement.
It only leaks when the tap is used
Check both the supply hose under pressure and the waste connections. Movement when operating the tap can also reveal a loose tap base or strain on the hose.
Compare your options
Gently tighten existing connection
Best for: A minor drip clearly coming from a hose nut that may have loosened
Pros: Quick, simple, no new parts if it works
Cons: Only helps if looseness is the real cause; overtightening can make things worse
Remove and reseat with a new seal
Best for: Leaks from a connection where the hose and fittings are otherwise in good condition
Pros: Addresses damaged or displaced washers or O-rings
Cons: Requires the correct replacement seal and careful refitting
Replace the whole flexi hose
Best for: Leaks from the hose body, braid, crimped ends, corrosion, bulging or old damaged hoses
Pros: Most reliable fix for hose failure
Cons: Needs the correct matching hose and access to both ends
| Option | Best for | Pros | Cons |
|---|---|---|---|
| Gently tighten existing connection | A minor drip clearly coming from a hose nut that may have loosened | Quick, simple, no new parts if it works | Only helps if looseness is the real cause; overtightening can make things worse |
| Remove and reseat with a new seal | Leaks from a connection where the hose and fittings are otherwise in good condition | Addresses damaged or displaced washers or O-rings | Requires the correct replacement seal and careful refitting |
| Replace the whole flexi hose | Leaks from the hose body, braid, crimped ends, corrosion, bulging or old damaged hoses | Most reliable fix for hose failure | Needs the correct matching hose and access to both ends |
Alternatives
- If the leak is actually from a faulty isolation valve rather than the flexi hose, replace the valve instead of the hose
- If access is very poor, removing the tap assembly first may make hose replacement easier, but this adds complexity
Pro tips
- Take a clear photo of both ends of the old hose before buying a replacement so you can match the fittings properly
- Keep the old hose until the new one is installed successfully, as a reference for length and connection type
- After fixing the leak, check the cabinet base and nearby panels for trapped moisture and dry them out to prevent swelling or mould
- If one hose has deteriorated with age, inspect the other under-sink supply hose as well
Safety notes
- Turn off the water supply before loosening any hose connection
- If there are electrical sockets or powered appliances in the sink cabinet, isolate power before working around water
- Do not use makeshift repairs on a pressurised water supply hose
- Use two spanners where needed so you do not twist connected pipework or damage the tap
Legal & regulatory notes
Plumbing rules vary by country and region. In some places, replacing supply hoses or valves may be restricted work or may need to comply with local water regulations. Check local requirements if you are unsure, especially for rented properties, shared buildings or any work beyond a straightforward like-for-like replacement.
What this guide does not cover: This guide covers diagnosing and fixing a typical leaking water supply flexi hose under a sink. It does not cover waste pipe leaks, mixer tap internal faults, concealed plumbing inside walls, or region-specific certification requirements for plumbing work.
Cost considerations
A simple reseat or seal replacement is usually the lowest-cost outcome. Replacing the full flexi hose costs more in parts but is often the most sensible option if the hose shows wear. Delaying repairs can increase costs through cabinet damage, flooring damage or mould.
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 these directories of real, verified trade businesses. Compare local tradespeople, read their details and request quotes before you commit.
Frequently asked questions
Can I use PTFE tape on a leaking flexi hose connection?+
Only if that specific fitting is designed to seal on the thread. Many flexi hose connections seal with a washer or flat-faced seal, not the thread, so tape will not fix the real problem and may interfere with proper seating. Check the hose or tap manufacturer guidance.
Can I repair a split braided hose instead of replacing it?+
No. A split hose or leaking crimped end should be replaced. Tape, glue and clamp-type patches are not reliable for a pressurised potable water supply.
How do I know if the hose is the wrong type?+
If the threads do not start smoothly by hand, the sealing faces do not match, or the hose is under tension or forced into a tight bend, it may be the wrong fitting or unsuitable length. Compare it with the old hose and the tap or valve requirements.
Should I replace both hot and cold flexi hoses at the same time?+
Not always, but if both are of similar age and one has clearly deteriorated, it is sensible to inspect the other closely and consider replacing it too.
What if I cannot turn off the water under the sink?+
Use the main water shut-off instead. If there is no reliable way to isolate the supply, or the valve leaks when operated, stop and arrange professional help.
Sources & references
Guidance on this page is traced to documented sources. Last checked 25 September 2026.
- John Guest - Installation and Maintenance Instructions · manufacturer
Supports good practice on correct installation, avoiding strain and misuse, and following manufacturer fitting instructions.
- WRAS - Water Regulations and Approved Products · industry
Supports the point that plumbing products and work should comply with applicable water regulations and approved product requirements.
Basic fault-finding and replacement practice for sink flexi hoses changes slowly, though product-specific fittings and local plumbing rules can vary.