What’s Wrong With My Toilet?
Pick the symptom — get the likely cause, the DIY fix, and the exact part. From a licensed plumber.
General guidance from a licensed plumber, not a substitute for an on-site inspection. As an Amazon Associate, Plumbing Picks may earn from qualifying purchases at no cost to you.
Toilet troubleshooting — quick answers
What’s the most common toilet problem?
A running toilet, and the usual culprit is a worn flapper — the rubber seal at the bottom of the tank. It’s a small part and a 10-minute fix, and it’s also the #1 hidden cause of a high water bill.
How do I know if it’s the flapper or the fill valve?
Put a few drops of food coloring in the tank and wait 10 minutes without flushing. If color seeps into the bowl, the flapper is leaking. If the tank water stays clear but you hear the valve cycle on and off, or the water keeps running into the overflow tube, the fill valve (or float height) is the problem.
When should I call a plumber instead of DIYing it?
Call a pro if the bowl overflows repeatedly after plunging and augering (a deeper drain or vent blockage), if multiple fixtures gurgle at once (possible main-line issue), or if water leaks from the base every flush after you’ve reset the wax ring. Those point past the toilet itself.
Frequently asked questions
What is the most common toilet problem?
A running toilet, usually caused by a worn flapper — the rubber seal at the bottom of the tank. It is a small part and a 10-minute fix, and it is also the most common hidden cause of a high water bill.
How do I know if it is the flapper or the fill valve?
Put a few drops of food coloring in the tank and wait 10 minutes without flushing. If color seeps into the bowl, the flapper is leaking. If the water stays clear but you hear the valve cycle, or water runs into the overflow tube, the fill valve or float height is the problem.
When should I call a plumber for a toilet?
Call a pro if the bowl overflows repeatedly after plunging and augering, if multiple fixtures gurgle at once, or if water leaks from the base every flush after resetting the wax ring. Those point past the toilet to the drain line, vent, or flange.
How to use the diagnostic
Answer the questions with the tank lid off and the water still on, so you can watch the flapper, fill valve and float as the toilet runs or refills. Most running, weak-flush and slow-refill problems come from a handful of inexpensive tank parts, and the diagnostic points you to the guide for the part that matches what you see. Write down the brand and model printed inside the tank before you shop, since flappers and fill valves come in 2-inch and 3-inch versions.
Water on the floor around the base, cracks in the bowl or tank, or sewage smells point to problems outside the tank. Shut off the supply valve behind the toilet and have a plumber look at those.