In short
Under-sink leaks come from four places: the supply lines, the angle stops, the trap, or the drain where it meets the sink. In many older Rosemead kitchens, the original chrome traps have thinned out. We dry everything, find the first wet spot, fix that part, and check it again after the water runs.
Your photo checklist
- The cabinet floor, after one wipe-down
- The hoses from the angle stops
- The angle stops themselves
- The trap and the nuts on each end
- Any soft or swollen cabinet wood
Covered on a Rosemead visit
- Braided or old copper supply lines replaced
- Weeping or seized angle stops swapped for quarter-turn valves
- Leaks at the faucet base and sprayer hose fixed
- Dripping P-traps, slip nuts and tailpieces replaced
- Basket strainers and pop-up drains resealed
- Dishwasher and disposal connections under the sink tightened or redone
Outside what we take on
- Gas piping of any kind past the existing flex connector.
- Roof, foundation and structural repairs.
- Tearing out and rebuilding a whole bathroom or kitchen.
Why Rosemead sinks start leaking
Rosemead’s housing has a 1959 median build year, and many kitchens and baths still have multi-turn shutoff valves that have not been turned in years. When someone finally closes one to swap a faucet, the packing nut starts to weep, and that slow drip is a common cause of a damp cabinet floor.
Hard water adds scale to the joints and valve stems, so a supply line or faucet connection that looked fine can start dripping after a part nearby is disturbed. We replace worn valves and lines together so one fix doesn’t start the next leak.
How we find the leak
Dry everything
The cabinet is emptied and wiped so a fresh drip shows up.
Run each part
Hot, cold, faucet and drain are tested one at a time.
Replace the part
The failed line, valve, seal or trap section is swapped.
Watch it
Water runs while we check every joint with a dry towel.
Bigger jobs, free estimate
Water coming from inside the wall or the floor, or a drain line clogged past the trap, is a bigger plumbing job with its own free estimate. If water has damaged the cabinet floor, we can replace the panel after the leak is fixed. Leaks that appear only while the sink is draining are on the drain side, covered on the P-trap and sink drain page.
While we’re out for this, Rosemead customers often add faucet installation, P-trap and sink drain repair, shutoff valve replacement, faucet repair and replacement or garbage disposal repair and replacement.
What to text
A photo inside the cabinet with the door open, close-ups of the valves and the drain, and where you see the water.
Under-sink leak questions
Why is there water under my kitchen sink?
Usually a supply line, shutoff valve, faucet base or drain joint. Drying the cabinet and running each one shows which.
What should I do first when the sink is leaking?
Close the shutoff valves under the sink, put a bowl under the drip, and text a photo. Most leaks wait safely once the valve is shut.
Why does my sink only leak when I run the water?
That points to the drain: a loose slip nut, cracked trap or dried strainer seal.
Can a handyman fix an under-sink leak?
Yes. Supply lines, shutoffs, faucet connections and traps are routine repairs.
How much does it cost to fix a leak under the sink?
It depends on which part failed. Text a photo for a free estimate.
Should I replace both supply lines?
Usually. If one is old or corroded, the other usually is too, so we often swap both.
How do I find which part under the sink is leaking?
Dry everything, put a paper towel under each joint, then run water. The wet towel points to the supply line, valve, drain or faucet base.
Is the swollen cabinet floor ruined?
Particleboard that has swelled won’t go flat again. Once the leak is fixed we can cut in a new floor panel or add a waterproof liner.
Why is the pipe under my sink leaking?
Slip-joint nuts on plastic traps loosen, and washers flatten over time. Tightening or new washers usually fixes it. A cracked trap needs replacing.
What affects the cost of an under-sink leak repair?
The part involved, how corroded the old fittings are, and whether the cabinet floor is damaged. A photo lets us quote it before we come.
Jobs that pair with this one
- P-trap and sink drain repairTrap leaks.
- Shutoff valve replacementValve leaks.
- Faucet repairFaucet drips.
- Garbage disposal repairDisposal leaks.
Related guide: Under-sink leak repair tips from our guide to under sink leaks and supply lines.
Plumbing tips for Rosemead homes
- Tracking down a leak under the sinkLeak under your kitchen or bathroom sink? Find out if it’s the supply line, shutoff, faucet or drain, and text a photo for a free estimate in Rosemead.
- When the garbage disposal hums, leaks or quitsHow to clear a humming or dead garbage disposal, when to replace it, and what to expect when we swap one in a Rosemead kitchen.
Jobs like this one are everyday work for our Rosemead handyman service, from the blocks off Garvey Avenue to the streets near Rosemead Park. A photo by text gets you a quote first.
Part of plumbing repairs. You can also browse all our services or read about repairs in postwar Rosemead homes.