Kitchen sink leaking underneath: the usual causes
There are three usual places to look: the bottle trap and waste joints that carry water to the drain, the flexible hoses and tap connections that bring water to the tap, and the seal where the sink meets the countertop.
When you check for a sink leaking under cabinet storage, look for the signs PUB lists: dripping taps and water stains, mould or peeling material under the sink. PUB says a leaking tap can lose up to 2 litres of water per hour, and that prolonged leaks lead to high water bills, water wastage and possible damage to your property.
Find the source step by step
You need only a torch and some dry tissue.
- Empty and dry the cabinet. Take everything out and dry the trap, pipes, hoses and cabinet base so fresh water stands out.
- Run the tap with the plug out. Watch the bottle trap and waste pipe with the torch, holding dry tissue under each joint.
- Fill and release the sink. Fill the bowl, pull the plug and watch the trap and waste pipe as the water drains.
- Check the hoses with the tap on. Wipe each flexible hose and its connections with dry tissue while the tap runs.
- Check the countertop edge. Wipe water along the sink rim, then use the torch to look under the rim for drips.
- Do a meter test. If you suspect a supply leak, PUB suggests turning off all taps and water-using appliances and watching the water meter for at least 10 minutes. If the dial moves, there is a leak.
Trap and waste joints
HDB says the common trap for kitchen sinks in HDB flats is the bottle trap, and that chokes come from solid matter or hardened grease. To clear it, HDB says to twist the lower section off anti-clockwise, remove the solid matter with a wire hook or thin stick, flush with water, and screw the section back clockwise.
A sink trap leak at the joint after a choke may mean the trap needs to be replaced.
FROM THE HOMEZYPRO DIRECTORY
Published bottle trap replacement rates
For the most common unit (per job), the lowest published bottle trap replacement rates from 10 companies run from S$40 to S$100 per job (middle rate S$50), to replace one kitchen sink trap. The middle figure is a real published rate, not an average. Each figure is one company's own advertised rate with its conditions, not a quote.
See 10 published bottle trap replacement rates and sources
| Company | Service as listed | Rate | Source |
|---|---|---|---|
| Plumber - Singapore Plumbing 24hrs | Supply & Replace Water Trap for Kitchen Sink | From S$40 per job | singaporeplumbing24hrs.com.sg |
| GD Plumbing | Replace bottle trap for kitchen sink | From S$50 per job | gdplumbing.com.sg |
| Home Plumbers Singapore | Supply and replace a kitchen-sink bottle trap | From S$50 per job | homeplumbers.com.sg |
| SG1 Plumber Singapore | Sink Bottle Trap Replacement | S$50 per job | sg1plumber.com |
| Sin Plumbing Singapore | Supply & replace bottle trap for kitchen sink | From S$50 per job | sinplumbing.com |
| Uncle Plumber | Supply and Replace bottle trap for kitchen sink | From S$50 per job | uncleplumber.sg |
| Kiasu Plumber | Supply & install bottle trap (kitchen sink) | From S$80 per job | kiasuplumber.com |
| Best Plumbing | Supply & replace bottle trap for kitchen sink | From S$100 per job | bestplumbing.com.sg |
| SR Power Plumber Pte. Ltd. | Supply & replace bottle trap for kitchen sink | From S$100 per job | srpowerplumber.com |
| Summer Plumbing Service | Supply & replace bottle trap for kitchen sink | From S$100 per job | sgplumbing.com.sg |
10 companies publish a rate to replace one kitchen sink trap, all per job. As printed, their rates run from S$40 to S$100 per job, with S$50 per job in the middle, which is one company's real published rate, not an average. Most lines say "supply", but ask whether the trap is included. For other jobs, see our plumbing costs page.
Hoses and tap connections
Flexible hoses connect the tap to the water supply. HDB says leaking pipe joints come from use and deterioration over time, or from impact, and advises engaging a licensed plumber for repairs where necessary. For a leak, HDB says to shut the stopcock at the water sub-meter.
If the drip comes from the tap body itself, HDB notes that a tap usually leaks when the washer is worn out. See our guide to fixing a leaking tap.
FROM THE HOMEZYPRO DIRECTORY
Published flexible hose replacement rates
For the most common unit (per job), the lowest published flexible hose replacement rates from 10 companies run from S$40 to S$110 per job, to replace one sink, basin or cistern hose.
See 10 published flexible hose replacement rates and sources
| Company | Service as listed | Rate | Source |
|---|---|---|---|
| Anytime Plumber.sg | Replace Sink/Basin/Cistern flexible hose | From S$40 per job | anytimeplumber.sg |
| GD Plumbing | Replace Sink/Basin/ Cistern flexible hose | From S$40 per job | gdplumbing.com.sg |
| Home Plumbers Singapore | Replace a sink, basin or cistern flexible hose | S$40 to S$60 per job | homeplumbers.com.sg |
| Sin Plumbing Singapore | Replace Sink/Basin/Cistern flexible hose | From S$40 per job | sinplumbing.com |
| Uncle Plumber | Replacement of sink/basin/Cistern flexible hose | From S$40 per job | uncleplumber.sg |
| Ace Plumbing Specialist | Replace sink / basin / cistern flexible hose | From S$90 per job | aceplumbing.sg |
| EZ Plumber SG | Or cistern flexible hose | S$100 per job | ezplumber.sg |
| Best Plumbing | Replace Sink/ Basin/ Cistern flexible hose | From S$110 per job | bestplumbing.com.sg |
| SR Power Plumber Pte. Ltd. | Replace sink / basin / cistern flexible hose | From S$110 per job | srpowerplumber.com |
| Summer Plumbing Service | Replace Sink/ Basin/ Cistern flexible hose | From S$110 per job | sgplumbing.com.sg |
10 companies publish a rate to replace one sink, basin or cistern hose, all per job. As printed, their rates run from S$40 to S$110 per job; half of them start at S$40. One line is printed as a range, S$40 to S$60 per job, and the S$100 per job line is for a cistern hose.
No line in these tables prices a leaking waste pipe, a cabinet base or water damage repair, so ask for a quote on those. If the tap itself needs changing, see our tap replacement cost guide.
Sink seal and countertop
If the countertop check shows water running under the sink rim, that points to the seal between the sink and the countertop. A plumber or handyman can reseal or refit the sink. Ask what the job includes.
HDB notes there is no waterproofing membrane under kitchen tiles and advises mopping rather than washing the kitchen floor. If water from under your sink has reached the flat below, read our guide to a ceiling leak from upstairs.
NEXT STEP
See plumbing companies in the directory with their published prices, the areas they say they cover and their sources.
Compare plumbersWhen to stop and call a professional
Stop your checks and call a professional if you see any of these:
- water near power points under the sink
- a leak you cannot trace
- a cracked sink
- damage to the cabinet base
- water in the flat below
Shut the stopcock at the water sub-meter, take photos of the leak, and ask for a quote that names the part to be replaced. Our leak repair page is a good place to start.
PUB's leak tips say to always engage a licensed plumber to detect and repair leaks. PUB also advises discussing scope and cost first, asking for itemised quotes and getting at least three quotes.
Questions
Can I fix a leaking sink trap myself?
If the bottle trap is choked, you can clear it with HDB's method: twist the lower section off anti-clockwise, remove the solid matter, flush with water and screw it back clockwise. If the joint still leaks, the trap may need replacing. PUB lists installing or replacing a sink and its trap among the simple works a handyman may do.
How much does it cost to replace a kitchen sink trap?
10 companies publish a rate to replace one kitchen sink trap. As printed, their rates run from S$40 to S$100 per job, with S$50 per job in the middle, which is one company's real published rate, not an average. Most lines say "supply", but ask whether the trap itself is included.
Why does my sink only leak when I run the tap?
It points to a part that carries water while the tap runs: the trap and waste joints as the sink drains, or the tap itself. Check those with a torch and dry tissue. If the tap body drips, HDB says a tap usually leaks when the washer is worn out.
Do I need a licensed plumber to replace a flexible hose?
PUB lists the simple works a handyman may do, including replacing or removing a tap or mixer, replacing a shower hose and installing or replacing a sink and its trap. A sink flexible hose is not named on that list, so ask the company whether a PUB Licensed Plumber will do the job. Other regulated water service work needs a PUB Licensed Plumber.
Can a leak under my sink damage the flat below?
It can if the water reaches the flat below as a ceiling leak. HDB says untreated ceiling leaks may damage electrical items and cause mould growth, and for a leak between two flats the owners arrange the repair and split the costs. Fix the source and talk to your neighbour.
How do I stop the leak until the plumber arrives?
For a supply leak, HDB says to shut the stopcock at the water sub-meter to cut the water supply. For a leak at the trap or waste pipe, stop using the sink and place a container under the drip. Take photos to show the plumber.
Prices come only from the sourced company rates in the HomezyPro directory, shown with each company and its source.
Practical guidance for planning a home job in Singapore. Company prices come from the HomezyPro directory, each linked to its source; rules and safety points link to the agency or manufacturer that sets them. This is not a site inspection, a quote or professional advice for your home.
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