The most common causes for a weak flush / poor flush:
1. Clogged sewer line or clogged toilet bowl
Symptoms: When flushing, the toilet’s water level would rise in the bowl and slowly drain. This is a telltale sign that your toilet is clogged
Solution: Try plunging your toilet or using a closet auger to see if the stoppage can be dislodged. If you are unable to remove the blockage, you may need to contact a local plumber for assistance.
2. Clogged vent line
Symptoms: You notice that your toilet gurgles or that bubbles blow out during the flush, or you just get a weak flush that may leave materials behind in the bowl.
Every appliance that drains into the sewer line has a vertical vent line that allows air to enter the pipe. (These are the pipes that are sticking up thru your roof) The vent must be open to allow air to come in behind the water and waste as they flow through the pipes. Without the air coming in through the vent, a vacuum is created by the water flow. The vacuum slows down the flow of the waste, which can cause solids to settle out and cause a line clog. There are many reasons why a vent pipe would get clogged, including:
There is a simple test that you can run to verify you have a clogged vent pipe. Take a large bucket of water and pour it quickly into the toilet bowl. If the vent pipe is clear, the water will go down the drain as fast as you can pour it. If the vent is clogged, the water level in the bowl will rise as the vacuum forms. Stop pouring if the water level rises, as we don’t want to overflow the bowl.
Solutions: Whatever is obstructing the vent pipe needs to be removed. The easiest way to do this is to take a garden hose up onto the roof, and run water down into the vent pipe. This water will force the obstruction down into the sewer pipe, clearing the vent. Because of the risk of fall, you may want to hire a professional to do this.
3. Incorrect settings or worn out toilet parts
Symptoms: When you flush your toilet, the flush seems very weak or it flushes well every other flush.
Solutions: Incorrect Settings: The water level in the tank should be about ½ inch below the top of the overflow tube. The chain on the flapper should only have 1 or 2 links of slack and the black refill tube from the fill valve, should be flowing water into the overflow tube during the refill.
Worn out parts: A worn out flapper, fill valve, trip lever or flush valve may be causing the flushing problem. See our FAQ titled: How to determine if you need toilet replacement parts.