Toilet Won't Flush Properly
Updated February 20, 2026
Weak flush, incomplete, or multiple flushes to clear? Tank water level too low, clogged rim holes, flapper closing too fast, or partial clog in the trap or drain.
Overview
Not enough water, not fast enough, no siphon. Volume or rate is reduced. Tank not full enough? Volume problem. Rim holes clogged? Water cannot enter fast enough. Flapper drops too quickly? Tank does not empty. Partial clog in the trap? Bowl cannot evacuate. Most fixes are simple, cheap, and under 30 minutes.
Symptoms
- Weak swirl instead of a strong vortex
- Two or three flushes to clear waste
- Bowl water level drops lower than normal, refills slowly
- Hear the flush but bowl does not empty -- siphon never engages
- Gradually weakened over weeks or months -- mineral buildup or developing clog
- Some flushes weak, others fine -- flapper or partial clog
Common Causes
- Tank level too low -- needs to be 1 inch below the overflow tube. Float too low or fill valve not completing. Most common cause, easiest fix.
- Clogged rim holes -- mineral deposits block the small angled holes under the rim. Reduced volume and speed entering the bowl. Mirror check: white or orange buildup visible.
- Waterlogged flapper -- absorbs water, gets heavier, drops too fast. Tank does not empty enough to create a full siphon.
- Partial clog in the trapway -- accumulated waste, excess paper, or non-flushable items. Restricts flow without fully blocking.
- Blocked vent -- bird nest, debris, ice. No air means no siphon. Often affects multiple fixtures, not just the toilet.
What You'll Need
How to Fix It
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Check and Adjust the Tank Water Level
Lid off. Water level should be 1 inch below the overflow tube. Lower? Adjust the float. Ball float: bend arm up or turn the screw. Cylinder float: squeeze clip, slide up. Flush, verify. Fill valve not shutting off at the right level? Clean or replace.
Tip: Mark the correct level with a permanent marker inside the tank. Quick visual reference for future checks. -
Clean the Rim Jet Holes
Mirror under the rim. Small angled holes blocked with mineral deposits? Wire, Allen wrench, or paper clip to poke through each hole. Thorough cleaning: plug the holes with putty or tape, pour vinegar into the overflow tube (feeds into the rim channel), soak overnight. Remove putty, flush several times.
Tip: Siphon jet hole at the bottom of the bowl is even more critical. Clogged? Flush will be dramatically weaker. Wire brush or vinegar soak. -
Inspect and Replace the Flapper
Water off, flush. Lift the flapper: heavy, waterlogged, soft, warped? Replace. Match to your model. Chain with half inch of slack. Should stay open until tank is 80% empty. Closes too fast with new flapper? Chain too long, getting caught.
Tip: Some flappers have an adjustable float or dial for open time. Set to maximum for the strongest flush. -
Plunge to Clear a Partial Clog
Water level and flapper fine, still weak? Partial clog. Flange plunger (extended rubber flap) over the drain, submerged. Plunge 15-20 times. Flush improves? Partial clog was the issue.
Tip: Plunging does not help? Toilet auger (closet auger) reaches deeper into the trapway. Breaks through what a plunger cannot. -
Check for Vent Issues
Gurgling from nearby drains, slow draining elsewhere, sewer smell? Vent blocked. Roof: check the opening for debris, nests, leaves, ice. Garden hose flush. Cannot access or problem persists? Plumber.
Warning: Roof work carries fall risk. Sturdy ladder, spotter, non-slip shoes. Not comfortable with heights? Skip and call a plumber. -
Test After Each Fix
Test after each fix with wadded toilet paper. Strong vortex, single flush clears, refills in 30-60 seconds. Still weak after all steps? Toilet design limitation (early 1.6 GPF models are notorious) or permanent mineral scaling in the trapway.
When to Call a Pro
Call a plumber if weak flush persists after all steps, if multiple toilets are weak (main drain or vent), if you cannot safely check the roof vent, or if it is an older low-flow that has never flushed well. Camera inspection can check for blockages or pipe bellies.
Prevention Tips
- Tank level yearly. 1 inch below the overflow tube. Adjust the float if needed.
- Vinegar on rim holes and siphon jet every 6-12 months. Mineral buildup is progressive -- easier to prevent than remove.
- Flapper every 3-5 years. Waterlogged = closes too fast = weak flush.
- Only human waste and toilet paper. No wipes, hygiene products, swabs, floss, or paper towels. Partial clogs before full blocks.
- Hard water? Softener reduces deposits in rim holes, supply lines, and throughout the system.
- Replacing the toilet? MaP score of 600 or higher. Strong flush at 1.28 GPF efficiency.