Plumbing · Lesson 11 of 13Beginner5 min read

Troubleshooting by Symptom

Good troubleshooting starts with three questions. Is it the supply or the drains? Is it one fixture or the whole house? Hot, cold, or both? The answers point to a system, and the system points to a fix. This finder walks you through the common problems.

Think like a plumber

Supply or drain? Water that won’t come out, or comes out wrong, is a supply problem. Water that won’t go away, or smells, is a drain problem.
One fixture or many? A problem at one faucet is usually at that faucet. A problem everywhere is usually at the main, the meter, the pressure-reducing valve, the water heater or the building drain.
Hot, cold, or both? A hot-only problem points to the water heater or the hot lines.
When did it start? After a cold night, after work on the street, after a new appliance? The timing is a clue.
Know when to stop. Water spraying or pouring: close the main shutoff first (Shut Off Your Home’s Water). The smell of gas: leave the house and call from outside. Sewage backing up: stop running water. The finder marks these.

Causes are listed roughly from the most common and simplest to check to the less common. A licensed plumber and your local code have the final word.

Sounds, smells and sights, and what they often mean
Clue	What it often means
Toilet refills on its own every so often	Water leaking past a worn flapper (EPA)
Water trickling into the toilet’s overflow tube	Tank water level set too high
Sewer smell from a drain nobody uses	Its trap has dried out; run water into it (Union Sanitary District)
Gurgling drains, water moving in the trap	Poor or blocked venting, or a clog downstream (HUD)
Bang when a valve closes	Water hammer (U.S. Army); possibly high pressure from a failing PRV
High-pitched whistle in the pipes	A failing pressure-reducing valve (City of San Diego)
Rust-colored water, mostly from hot taps	Corroding galvanized steel pipe (HUD) or the water heater
White crust on faucets and showerheads	Hard water scale (USGS)
Soot on top of a gas water heater	A clogged flue: stop using it and call a pro (HUD)
Water dripping from the T&P discharge pipe	High temperature or pressure, or a worn valve; never cap it
Soggy ground and sewage odor over a drainfield	A failing septic system (HUD, EPA)

Before you call a plumber

Know where your main shutoff is, and close it if water is getting where it shouldn’t.
Write down the symptoms: which fixtures, hot or cold, when it started, what you’ve tried.
Check whether the plumber is licensed where you live; the Bureau of Labor Statistics notes most states and some localities require it. Ask whether the job needs a permit.
Get a written estimate for anything beyond a simple repair.

Check yourself

Tap an answer to check it, or open “Show the answer.”

Water is spraying from a pipe under the sink. What do you do first?
Show the answer
Close the fixture valve or the main shutoff. Stop the water first, then deal with the repair.
Only the hot water has low pressure. Where would you look?
Show the answer
The water heater and hot lines. A hot-only problem points to the heater, its valves or the hot piping.
Every drain in the house is slow and the lowest one backs up. What’s likely?
Show the answer
A blockage in the building drain or sewer, or a full septic system. Many fixtures at once means a problem downstream of all of them.
You smell gas near the water heater. What’s the right move?
Show the answer
Leave the house and call the gas company or 911 from outside. CPSC: leave immediately, and call from a neighbor’s house.

Go deeper

Being an Adult 101: Fix a Running Toilet Fix a running toilet.
Being an Adult 101: Unclog a Sink or Toilet Unclog a sink or toilet.
Being an Adult 101: Shut Off Your Home's Water Shut off your home’s water.
U.S. EPA WaterSense: Fix a Leak Week EPA’s leak checks.

Sources

The finder also draws on these sources:

I finished this lessonSaved on this device only.

A free course from Teddy Rook Book. It explains how plumbing works in general and follows U.S. sources; your local plumbing code, the authority having jurisdiction and manufacturers’ instructions are the final word.