Toilet Doesn't Fully Flush: Fix It Yourself (Troubleshooting Guide)

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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

If your toilet doesn't fully flush, check for a clogged trap or low water level. Use a plunger or toilet auger to clear blockages and adjust the float to increase the fill level.

Confirm the symptom

Toilet doesn't fully flush even with strong water flow
Water level in bowl is lower than usual
Toilet requires multiple flushes to clear waste
Water continues to run after flushing

Tools and prep

Rubber plunger
Toilet auger (snake)
Adjustable wrench
Screwdriver
Bucket
Work gloves
Turn off water supply to toilet before starting

Step-by-step troubleshooting

Check Water Level in Tank
Do: Lift the tank lid and check the water level. It should be about 1 inch below the overflow tube.
Observe: Low water level or water not filling properly
Means: Insufficient water in the tank can lead to weak flushes.
Next: Adjust the float to raise the water level.
Adjust the Float
Do: Locate the float and adjust it upward to increase the water level in the tank.
Observe: Water level rises to the correct height.
Means: Proper water level ensures a strong flush.
Next: Test the toilet by flushing.
Check for Clogged Trap
Do: Use a plunger to try and clear any blockage in the trap. If it doesn't work, use a toilet auger.
Observe: Water drains more freely after plunging or augering.
Means: A clogged trap can prevent proper flushing.
Next: If the trap is clear, move to the next step.
Inspect Flapper Valve
Do: Check if the flapper valve is opening fully when you flush. If it's worn or damaged, replace it.
Observe: Flapper doesn't open fully or closes too soon.
Means: A faulty flapper can restrict water flow to the bowl.
Next: Replace the flapper valve if necessary.
Check Flush Valve
Do: Ensure the flush valve is not clogged or damaged. Clean or replace if needed.
Observe: Flush valve is clear and functioning properly.
Means: A clogged or damaged flush valve can hinder water flow.
Next: Test the toilet by flushing again.
Test the Flush
Do: Flush the toilet and observe the water flow and how well it clears the bowl.
Observe: Toilet flushes fully and drains properly.
Means: The issue is resolved if the toilet flushes completely.
Next: If the problem persists, consider professional help.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Low Water Level in Tank Insufficient water in the tank leads to a weak flush.	Common	Easy	Float adjustment or replacement
Clogged Trap A blockage in the trap prevents proper drainage.	Common	Easy–Medium	Toilet auger
Faulty Flapper Valve A worn or damaged flapper restricts water flow to the bowl.	Sometimes	Easy	Flapper valve replacement
Clogged or Damaged Flush Valve A clogged or damaged flush valve hinders water flow.	Sometimes	Medium	Flush valve cleaning or replacement
Incorrect Toilet Bowl Design Some older or low-flow toilets may not flush effectively.	Rare	Hard	Toilet replacement
Mineral Buildup in Pipes Hard water can cause mineral buildup that restricts water flow.	Sometimes	Medium	Pipe descaling or replacement

Parts matching

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

Float adjustment kit
Toilet plunger
Toilet auger
Replacement flapper valve
Flush valve cleaning kit
Water supply line repair kit

Purchase parts that match your toilet model for best results.

When to call a professional

If the toilet still doesn't flush properly after trying all DIY solutions
If there is significant water leakage from the tank or bowl
If you suspect a major clog in the main sewer line
If the toilet is old and requires replacement

FAQ

Why does my toilet not flush completely?

A toilet that doesn't flush completely can be caused by low water levels, a clogged trap, or a faulty flapper valve.

How can I increase the water level in my toilet tank?

Adjust the float mechanism to raise the water level in the tank to about 1 inch below the overflow tube.

Can a clogged trap cause a weak flush?

Yes, a clogged trap can restrict water flow and result in a weak or incomplete flush.

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

If the problem persists, it may be a more serious issue that requires a professional plumber to inspect and repair.