Two Puddles Under Two Sinks. Only One Keeps Growing

Imagine two homeowners open the cabinet beneath their sinks.
Both find water.
Same puddle. Same panic.
But then something interesting happens.
Homeowner A turns off the faucet. The dripping stops.
Homeowner B turns off the faucet. The dripping continues.
Those two details point toward very different plumbing problems.
Puddle A: It Only Leaks When Water Goes Down the Drain
Run the faucet and water appears beneath the sink.
Stop using it and the leak disappears.
Hmmm....
That pattern makes the drainage side worth investigating.
Possible sources include:
- a loose drain connection
-a leaking P-trap;
-a failed seal;
- damaged drain piping; or
-another connection underneath the sink
This type of leak often gives you a simple way to limit damage:
Stop using that sink until it's repaired.
Puddle B: It Leaks Even When Nobody Uses the Sink
This deserves more attention.
The hot and cold lines supplying the faucet remain under pressure even when the faucet is off.
So if water continues appearing underneath the cabinet with everything turned off, the problem may be on the water-supply side.
Possible sources include a supply line, shutoff valve, faucet connection, or nearby pressurized pipe.
Now "don't use the sink" may not be enough.
The water is already flowing without you.
Here's the 30-Second Test
Dry the cabinet.
Don't run the faucet.
Watch.
It stays dry?
Now briefly use the sink.
If the leak appears only while water drains, tell your plumber.
Water returns without using anything?
Treat the possibility of a supply=side leak more seriously.
If the leak is actively worsening, isolate the fixture using its shutoff Valves if you can safely do so.
If those valves don't stop the water, the home's main shutoff may be necessary.
Which Puddle Is The Emergency?
Neither location alone determines urgency.
The behavior of the water does.
Get urgent help if:
- water is spraying
-the leak won't stop
-a shutoff valve fails;
-the cabinet is rapidly flooding;
-water is entering the wall or flooring; or
-electrical equipment is getting wet.
A small drain leak that stops completely when you stop using the sink is usually easier to contain.
An uncontrolled pressurized leak is another story.
One Puddle. Two Very Different Questions.
Instead of telling the plumber:
"My sink is leaking"
Tell them:
"It only leaks when the sink drains."
Or:
"It keeps leaking even when we aren't using anything."
That's a much better starting point.
Because good plumbing diagnosis isn't just about where you found the water.
It's about when the water appears.
Under-Sink Leak in South Florida?
Leading Plumbing Services can determine whether the leak is coming from the drain, P-trap, supply line , shut off valve, faucet connection, or the surrounding plumbing.
Call or text Leading Plumbing Services: 561-506-6159
Same cabinet. Same puddle. Completely different plumbing problem.
Author: Nathanael Jolteus





