Guides · Install
Under-Sink Leak Prevention
The fittings that fail, the first-week checks that catch them, and the cheap hardware that turns a drip into a non-event.
Where under-sink leaks start
Almost never in the filter housing itself. The usual culprits are push-fit connectors that were not pushed fully home, a missing or pinched O-ring, over-tightened plastic threads, and tubing that was cut at an angle.
The second most common cause is water hammer or vibration slowly working a compression nut loose over months.
Install like a plumber
Cut tubing square with a proper cutter, not scissors. A ragged end will not seal in a push-fit fitting.
Push the tube in until it stops, then tug gently to confirm the collet has gripped. This single habit prevents most leaks.
Hand-tighten plastic threads, then a quarter turn at most. Do not use tape to rescue a cross-threaded fitting.
Support the tubing so its weight does not hang on the connector, and keep it away from the garbage disposal's moving parts.
Hardware worth buying
A small leak tray or pan under the system, with a water alarm puck. For the price of a takeaway meal, you get warning instead of a ruined cabinet floor.
A quarter-turn shut-off valve on the feed line, reachable without emptying the cabinet.
A drip tray under the faucet air gap and a check that the drain line cannot siphon back.
The first-week routine
Day one: dry every joint with a tissue and watch for ten minutes with the system running. Then check again after an hour.
Day two and day seven: run a finger along the underside of each connection and the housing threads. A dry finger means a dry joint.
After any cartridge change: repeat the ten-minute check. Most leaks happen right after someone has been working in there.
Look for mineral crust or a whitish ring, which marks a slow weep that has already dried more than once.
What to do when you find one
Shut off the feed before investigating, and put a towel down. Water travels along the cabinet floor and shows up somewhere else.
Reseat the fitting first — most leaks are seating, not hardware. Replace the O-ring if it is deformed, and replace the tubing if the end is compressed.
If a plastic manifold thread is cracked, stop. Thread sealant will not fix a crack and the manifold needs replacing.
After any repair, watch through a full filter cycle before closing the cabinet door and forgetting about it.
FAQ
Quick answers
+Should I use PTFE tape on push-fit fittings?
No. Push-fit connectors seal with an O-ring and a collet. Tape on the tube can prevent the collet from gripping and cause the leak it was meant to fix.
+How often should I check for leaks?
At every cartridge change, and once a month by touching the joints. Twice a year, look for dried mineral residue, which reveals slow weeps.
+Is a leak alarm worth it?
Yes for an under-sink system. It costs little and it converts a slow leak from a floor repair into a beep.