Try these checks in order
- 1
Check the tank water level
The water in the tank should sit about an inch below the overflow tube. A low level gives a weak flush.
- 2
Clear the rim jets
Mineral and debris can clog the small holes under the rim. A small mirror shows them. Poke them clear with a wire.
- 3
Use a flange plunger
A few firm plunges can clear a partial clog in the trap.
- 4
Test other fixtures
If a sink or tub also drains slowly, the problem is in the line, not the toilet.
Causes and fixes
| Cause | Sign | Fix |
|---|---|---|
| Low tank water | Weak flush, tank refills short | Adjust the fill valve |
| Clogged rim jets | Water trickles from under the rim | Clean the jets |
| Partial clog in the trap | Slow bowl, rising water | Plunge or use a closet auger |
| Blocked vent | Gurgling, slow flush | Clear the vent on the roof |
| Partial main line clog | Other fixtures also slow | Call a plumber to cable the line |
Slow toilet and slow sinks?
Call and describe what is slow. We can tell you whether it is the toilet or the line.
The vent can slow a toilet
Every drain needs a vent so air can follow the water. If the roof vent is blocked by leaves, a nest or debris, the drain can run slowly and gurgle. You may also hear a glug from a nearby sink as the toilet drains.
Clearing a roof vent is a job for someone comfortable and safe on a roof. A plumber can do it and check the rest of the line.
When the problem is the line
If the toilet is slow and another fixture is too, look at the branch or main line. Roots, grease or a belly can narrow the pipe. A cable and a camera locate the problem. See drain cleaning for what that involves.
If the toilet is also running, or if water is at the base, that is a different set of issues, see toilet repair.
Why a flush can look fine and still be weak
A toilet flush works by siphon action. Water rushes into the bowl fast enough to fill the trap and start a siphon that pulls the waste out. If the flow into the bowl is weak, because of clogged jets or low tank water, the siphon never fully starts and the bowl empties slowly.
That is why a slow toilet often has nothing in the drain. The problem is in how the water enters the bowl, not in how it leaves.
Hard water and rim jets
Mineral deposits are a common reason for blocked jets. The City reports that Bothell water is soft, so the problem is less common here, but it still happens, and rust or debris from old pipes can block the jets too. Cleaning is a ten-minute job.
Pour white vinegar into the overflow tube, let it sit, then flush. If the flush does not improve, clear the jets with a wire.
Before calling a plumber
- Tank water level checked
- Rim jets cleaned
- Plunged with a flange plunger
- Other drains tested for slowness
- Roof vent looked at from the ground
- Notes on when the problem started
Slow toilets in Bothell homes
Bothell has many mature trees, and in a wet climate leaves and moss collect on roofs and around vent pipes. Check that roof vents are clear in the fall. Older houses with cast iron or clay drains may also have scale or roots that slow the line.
If your house is served by the City of Bothell or Northshore Utility District for sewer, the public main is theirs, and the pipe on your lot is yours. A camera shows which side the problem is on. We serve Kenmore and nearby towns on our service areas page.
Vent sizing and drain slope follow the Uniform Plumbing Code (UPC) as adopted in WAC 51-56, and a poorly vented line is a common reason a toilet drains slowly without a clog.
Slow toilet questions
Mineral buildup in rim jets, scale in older cast iron drains and partial clogs are common. Roots in the lateral can also slow every fixture.
Yes. A blocked vent keeps air from following the water, so the drain runs slowly and may gurgle.
We advise against it. It can damage parts and leave caustic liquid in the bowl. Use a plunger or call a plumber.
Run other fixtures. If several are slow, or if water appears at a floor drain, the main line is the likely cause.
Modern toilets use less water and can be sensitive to clogs, but a well-designed one should flush well. Replacement may help an old poor design.
If a plunger does not help or if several fixtures are slow, call. Waiting risks a backup.