Small parts, big floods
Every sink and toilet in the house is fed by a short flexible supply line connected to a small valve on the wall called an angle stop. Those lines hold full house pressure all day. When one splits or a nut cracks, it can empty a lot of water into a cabinet, across a bathroom floor and down into the room below on a two-story home.
Plastic coupling nuts can crack with age or overtightening. Braided lines can corrode where the braid meets the fitting, and the rubber hose inside the braid ages the same way a washer hose does.
Isolating a burst supply line
- Find the angle stop.Look on the wall behind the toilet or inside the sink cabinet for a small oval or round handle where the line meets the wall.
- Turn it clockwise.Close it fully. Older multi-turn stops can be stiff; firm hand pressure only.
- Go to the main if needed.If the stop will not close or leaks itself, close the main shutoff instead.
- Relieve the line.Open the faucet or flush the toilet to release pressure and empty what is left.
- Dry the cabinet and floor.Empty the cabinet, dry the base and check the wall and ceiling below for water.
Where supply lines usually fail
| Failure point | What you see | Likely fix |
|---|---|---|
| Plastic toilet coupling nut | Spray or steady leak at the bottom of the tank | New supply line; avoid overtightening plastic nuts |
| Crimp where braid meets fitting | Rust or green corrosion, then a sudden burst | Replace the line and check its neighbors |
| Angle stop body or stem | Drip at the handle, or valve will not close | Replace the angle stop |
| Compression fitting at the wall | Slow weep around the nut | Reseat or replace the fitting |
| Pipe stub behind the wall | Water inside the wall, not the cabinet | Open the wall and repair the stub-out |
A house-wide supply line check
- Open each sink cabinet and look behind each toilet
- Note any line with rust, kinks, bulges or a cracked nut
- Try each angle stop gently to see if it turns
- Look for water stains on the cabinet floor or wall
- Check the ice maker and dishwasher supply lines too
- Make a list for the plumber so the work can be done in one visit
Common questions
Can I replace a supply line myself?
Many homeowners do, but if the angle stop will not close or the pipe behind it is corroded, a plumber should handle it so the wall connection is not damaged.
Why did water show up in the room below?
Water from a second-floor toilet or sink can travel along framing and come through the ceiling. Dry and open the ceiling if needed to prevent mold.
Do supply lines wear out?
Yes. Rubber inside braided lines ages, and plastic nuts become brittle. Replacing old lines is cheap insurance against a flood.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.