Toilet Not Flushing Completely

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Quick answer
Confirm the symptom
Tools and prep
Step-by-step troubleshooting
Common causes table
Parts matching
When to call a pro
FAQ
Related guides

Quick answer

A toilet that doesn't flush completely is often caused by a clogged trap or low water level. Check the flapper valve and water level in the tank. Use a plunger or auger to clear the trap if needed.

Confirm the symptom

Toilet water level rises slowly during flush
Toilet doesn't fully empty bowl
Weak siphon action in the bowl
Toilet requires multiple flushes to clear waste
Water in the tank is below the fill line

Tools and prep

Rubber plunger
Toilet auger (snake)
Adjustable wrench
Screwdriver
Bucket
Work gloves
Turn off water supply to toilet
Place bucket under tank to catch water if needed

Step-by-step troubleshooting

Check Water Level
Do: Remove the tank lid and check the water level in the tank.
Observe: Water level should be 1-2 inches below the overflow tube.
Means: Low water level reduces flushing power.
Next: Adjust float if water level is too low.
Test Flapper Valve
Do: Flush the toilet and observe the flapper valve.
Observe: Flapper should open fully and close properly.
Means: A faulty flapper restricts water flow.
Next: Replace flapper if it doesn't seal or open fully.
Use Plunger
Do: Use a rubber plunger to clear the bowl trap.
Observe: Water level drops and flushes normally after plunging.
Means: Clog in the trap is cleared.
Next: Flush the toilet to check if it works properly.
Use Toilet Auger
Do: Insert toilet auger into the bowl and rotate to clear the trap.
Observe: Resistance is felt and then released, indicating a clog is cleared.
Means: Clog in the trap is cleared.
Next: Flush the toilet to check if it works properly.
Inspect Trap and Drain
Do: Check for visible blockages in the trap or drain pipe.
Observe: Obvious clog is visible or felt with the auger.
Means: Clog is in the trap or drain pipe.
Next: Remove the clog with the auger or call a plumber.
Adjust Water Level
Do: Adjust the float to raise the water level in the tank.
Observe: Water level rises to 1-2 inches below the overflow tube.
Means: Increased water level improves flushing power.
Next: Flush the toilet to check if it works properly.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Clogged trap or drain Blockage in the trap or drain pipe prevents proper flushing.	Common	Easy–Medium	Toilet auger
Low water level in tank Insufficient water in the tank reduces flushing power.	Common	Easy	Float adjustment
Faulty flapper valve A damaged or worn flapper restricts water flow to the bowl.	Common	Easy	Flapper valve
Faulty fill valve A malfunctioning fill valve may not fill the tank properly.	Sometimes	Easy–Medium	Fill valve
Mineral buildup in trap Hard water deposits can restrict water flow in the trap.	Sometimes	Medium	Toilet auger
Incorrect toilet installation Improper installation can lead to poor flushing performance.	Rare	Hard	Plumbing services

Parts matching

Common parts needed to fix a toilet that doesn't flush completely include:

Rubber plunger
Toilet auger (snake)
Flapper valve
Fill valve
Adjustable float
Water supply line
Toilet tank-to-bowl bolts

Purchase parts that match your toilet model for compatibility.

When to call a professional

Clog persists after multiple attempts with plunger and auger
Toilet continues to not flush properly after adjusting water level and replacing parts
Water leaks from the base of the toilet
Toilet is making unusual noises during flush
Multiple toilets or drains in the house are slow

FAQ

Why is my toilet not flushing completely?

Common causes include a clogged trap, low water level in the tank, or a faulty flapper valve. Check these areas first to identify the issue.

How do I adjust the water level in my toilet tank?

Adjust the float mechanism attached to the fill valve. Raise the float to increase the water level in the tank, ensuring it's 1-2 inches below the overflow tube.

Can I use a regular plunger for a toilet clog?

Yes, a standard rubber plunger is effective for most toilet clogs. Ensure a good seal around the drain hole for optimal results.

What if my toilet still doesn't flush after trying these steps?

If the issue persists, there may be a deeper clog in the drain line or a plumbing issue. Call a licensed plumber to inspect and resolve the problem.

How often should I clean my toilet trap?

Clean the toilet trap every 6-12 months to prevent mineral buildup and maintain proper flushing performance.