Toilet Won't Flush or Has a Weak Flush
A toilet that won't flush is pretty high on the "need to fix this right now" list. The good news is that almost everything inside a toilet tank is cheap, simple, and replaceable with basic tools. Let's figure out what's going on.
What to Check Before You Call Someone
Check the water level in the tank
Lift the tank lid and look inside. The water level should be about an inch below the top of the overflow tube (the tall tube in the center). If the tank is low or empty, there's not enough water to create a proper flush.
Fix: If the water is low, check that the water supply valve behind the toilet is fully open (turn counterclockwise). If the valve is open but the tank won't fill, the fill valve is probably bad... a $10 part and a 15-minute swap.
Check the flapper and chain
The flapper is the rubber piece at the bottom of the tank that lifts when you push the handle. The chain connects the handle lever to the flapper. If the chain is too loose, the handle won't lift the flapper enough. If it's too tight or tangled, the flapper won't seal properly.
Fix: Adjust the chain so there's about half an inch of slack when the flapper is closed. If the flapper itself is warped, cracked, or doesn't feel smooth, replace it. Flappers are $5 at any hardware store and you just unhook the old one and hook on the new one. No tools needed.
Clear clogged jet holes under the rim
Look under the rim of the bowl... you'll see small holes (jet holes) where water flows in during a flush. In areas with hard water, mineral deposits can block these over time, weakening the flush significantly.
Fix: Use a small mirror to inspect them. Clear the holes with a piece of wire, a small Allen wrench, or an old toothbrush. For heavy mineral buildup, pour white vinegar into the overflow tube in the tank and let it sit overnight... it'll work its way out through the jets.
Check for a partial clog in the trap
If the flush is weak and the bowl drains slowly, there's probably a partial obstruction in the built-in trap. This is the S-shaped passage inside the porcelain. Things like excess toilet paper, "flushable" wipes (they're not actually flushable), or kids' toys can get lodged in there.
Fix: Use a plunger first... a real flange plunger, not a cup plunger. If that doesn't work, a toilet auger ($15-25) can reach into the trap and break up or retrieve the clog. Never use chemical drain cleaners in a toilet... they don't work well and can damage the porcelain.
Check the fill valve
If the tank takes forever to fill or makes a constant running/hissing sound, the fill valve is failing. A bad fill valve can mean the tank never reaches the proper water level for a full flush.
Fix: Replace the fill valve. A universal fill valve kit is $8-12 and takes about 20 minutes to install. Shut off the water supply, flush to empty the tank, swap the valve, turn water back on. Tons of tutorials online for this.
When It's Time to Replace
If the porcelain is cracked (you'll see water on the floor that isn't coming from supply lines or the wax ring), the toilet needs to be replaced. Cracked porcelain can't be reliably repaired. Also consider replacing if you have a pre-1994 toilet that uses 3.5-5 gallons per flush... modern toilets use 1.28 gallons and work better.
Read our full Toilet replacement guide →When to Call a Professional
Call a plumber if you've tried plunging and augering and the clog won't budge... it might be further down in the drain line. Also call if the toilet rocks on the floor (bad wax ring or flange issue) or if you see water damage on the ceiling below a second-floor bathroom.
This guide is for informational purposes. For gas leaks, electrical issues, or emergencies, call a licensed professional immediately.