Quick answer
A toilet that will not flush usually has a tank problem (low water, a worn flapper, a loose chain), blocked rim jets, or a partial clog. Check the tank first, then plunge with a flange plunger. If other drains are slow or gurgle too, the problem is likely in the main line, and plunging will not fix it.
Start by sorting out what kind of problem it is
Before touching anything, work out which of three situations you have. Each points to a different cause.
If the handle moves but the bowl barely flushes, the issue is often inside the tank or at the rim. If the bowl fills with water and drains very slowly, there is probably a partial clog. If water rises toward the rim, stop and read the overflow steps below before you flush again.
It also helps to ask whether this is one toilet or the whole house. Several fixtures acting up at once is a different story, covered near the end.
Cause 1: Low water level in the tank
HomeTips, a home repair reference, says the tank water should sit about 1/2 inch below the top of the overflow tube, and that a low level is fixed by adjusting the fill valve.
Take the lid off and look. If the water is well below that mark, start there. Follow your model's instructions for the adjustment.
Cause 2: A flapper or chain that is not doing its job
The flapper is the rubber piece at the bottom of the tank that lifts to release water into the bowl. A flapper that closes too soon cuts the flush short, and a loose or tangled chain affects how the flapper lifts.
HomeTips suggests watching the flapper during a flush. It should lift fully and stay open long enough for most of the tank water to move into the bowl. It also recommends leaving roughly 1/2 inch of slack in the lift chain.
Flappers wear out. The EPA's WaterSense program says most toilet leaks are caused by old or worn flappers and advises replacing them at least every five years. A worn flapper can also leak silently. To test for that, add a few drops of food coloring to the tank, wait 10 minutes without flushing, and see whether color shows up in the bowl. Flush right afterward so the tank does not stain.
Cause 3: Mineral buildup in the rim jets
Under the rim of the bowl are small holes that wash water around the bowl during a flush. When they clog with mineral deposits, the flush loses force and the bowl may not clear.
HomeTips recommends checking the holes with a small mirror and clearing deposits with a stiff wire, or soaking them in vinegar.
Cause 4: A partial clog in the trap or drain
A partial clog slows the water moving through the trap, so the flush is sluggish.
Many clogs come from what was flushed. The Pierce County, Washington sewer utility lists items that should never go down the toilet: cleaning and disinfecting wipes, hygiene wipes, diapers, paper towels, cotton swabs, and any consumer item that is not toilet paper. The City of Bellingham adds that even products labeled flushable do not actually break down in water. Bellevue's guidance also names dental floss, hair, and sanitary products.
If a toilet clogs repeatedly, review what goes into it. Anything that is not toilet paper belongs in the trash.
How to plunge a toilet safely
Use a flange plunger, the type with a sleeve that fits into the drain opening. HomeTips says it seals better than a flat plunger. A flat cup plunger is meant for sinks and tubs.
Lay towels around the base first.
- If the bowl is nearly full, do not flush again. Remove some water with a cup and bucket so it cannot overflow while you work.
- Lower the plunger so the flange sits fully in the drain opening and the cup fills with water. Tilt it slightly to push out trapped air.
- Press down gently first, then use steady vertical thrusts for about 20 seconds. This Old House describes alternating forceful and gentle plunges.
- HomeTips warns that rapid, aggressive plunging can push water past the wax seal and cause leaks at the base of the toilet, so keep the motion controlled.
- If the water drains, flush once to confirm the clog is gone. If not, repeat for at least a minute before trying again.
If the water keeps rising
If the bowl is climbing toward the rim, take off the tank lid and push the flapper closed to stop more water from entering. HomeTips also notes you can shut off the supply valve behind the toilet by turning it clockwise.
Shutting off the water stops the problem from getting worse while you decide what to do next.
A toilet auger is the next step
If plunging does not work, a toilet auger (also called a closet auger) is made for the job. HomeTips describes feeding the cable into the drain and turning the handle to break up or retrieve the blockage. Keep rags nearby, because augers can pull up wipes, toys, and debris.
HomeTips says that if an auger does not clear the blockage, it may be deeper in the line, which is a reason to call a professional.
What not to do
Some common reactions to a clogged toilet make things worse.
Chemical drain cleaners are the biggest one. HomeTips advises avoiding them because they can damage porcelain and pipes. The Poison Control center also describes strong alkali drain cleaners as very caustic, able to cause chemical burns on skin and in the lungs, and warns never to mix household cleaning products because of poisonous fumes. Poison Control also notes that lye can cause severe eye injuries. If a cleaner has already been poured into the bowl, splashing is a real risk, so do not plunge it. Tell any plumber who works on it that a chemical is in the bowl.
- Do not flush repeatedly. Each flush adds water and can cause an overflow.
- Do not mix cleaners, and do not add a second chemical on top of the first.
- Do not plunge hard enough to loosen the seal at the base of the toilet.
When it points to a vent or main line problem
Sometimes the toilet itself is fine. Plumbing vents let air into the drain system so wastewater can flow and water stays in the traps. HomeTips lists symptoms of a blocked vent: toilets that gurgle when flushed, slow drains, bowl water levels that rise or fall unexpectedly, and sewer smells.
HomeTips lists these signs of a main sewer line clog: multiple slow drains, gurgling toilets when other fixtures run, water backing up in tubs or showers, sewage odors, and standing water near floor drains. If only one fixture is affected, the clog is likely local. If several are, the sewer line is the likely cause.
If you suspect a main line problem, reduce water use right away. Skip the washing machine and limit toilet flushes and showers. Backups tend to show up first at the lowest drains in the house. Skip chemical drain cleaners here too, since they are usually ineffective on main line clogs.
The City of Bellevue and Pierce County both state that homeowners are responsible for issues in the sewer pipe on their own property. Check with your own city or sewer district about where its responsibility ends.
When to call Pyper Plumbing
Call a plumber when the plunger and auger have not worked, when the toilet keeps clogging again, or when it still runs or leaks after you adjusted the tank parts. Call right away if sewage backs up, if more than one fixture is affected, or if the problem seems to be getting worse.
Pyper Plumbing handles emergency plumbing repair, toilet repair and replacement, drain cleaning, and sewer line repair across Snohomish, Skagit, Whatcom, and Island counties. If a backup is active and you cannot stop it, shut off the water supply at the toilet or the main shutoff valve and call.
If your home is on a septic system, note that Pyper does not do septic work, and a septic contractor is the right call for that type of problem.
Common questions
Why does my toilet flush slowly or weakly?
HomeTips lists the usual causes: a low tank water level, a flapper that closes too soon, a loose or tangled lift chain, a partial clog, and mineral buildup in the rim jets. Check the tank first because those fixes are the simplest.
Is it safe to use drain cleaner in a clogged toilet?
Chemical drain cleaners are best avoided. HomeTips says they can damage porcelain and pipes, and Poison Control describes strong alkali cleaners as caustic enough to cause chemical burns. A flange plunger or toilet auger is a safer first step.
Are flushable wipes really safe to flush?
No. The City of Bellingham says that products labeled flushable do not actually break down in water. Pierce County lists wipes among the items that clog private sewer lines and public systems. Put wipes in the trash.
How do I know if the clog is in the main sewer line?
If several fixtures drain slowly, gurgle, or back up at the same time, the main line is the likely cause. A single toilet that is slow while everything else works is more likely a local clog.
Sources
Facts in this guide come from the following references. Local rules and manufacturer instructions can differ, so follow your utility and your equipment manual.
- HomeTips: Toilet Won't Flush
- HomeTips: Toilet Has Weak Flush
- HomeTips: Unclog a Toilet
- HomeTips: Plumbing Vent Problems
- HomeTips: Sewer Line Clog Signs
- HomeTips: Sink Gurgles When Toilet Flushes
- This Old House: How to Use a Plunger
- EPA WaterSense: Residential Toilets
- EPA WaterSense: Fix a Leak Week
- Pierce County, WA: Wipes Clog Pipes
- City of Bellingham: Keep Our Pipes Clear
- City of Bellevue: Preventing Sewer Backups
- Poison Control: Spring Cleaning
This guide is general information, not a substitute for an on-site inspection. If you smell natural gas, leave the building and call 911 or your gas utility. Pyper does not perform gas line work.
