This post will help you identify some possible reasons for your toilet's poor performance.
If the slow flushing toilet is on the ground floor, run water from a fixture higher than the toilet. Perhaps a tub on the second floor or a sink in the same restroom. Watch the toilet bowl. If you notice turbulence, if the water line appears to be getting higher or if you notice air bubbling, your sewer may be the culprit.
When the main sewer line to the building is becoming clogged or slow to drain, it will reveal itself in the way the toilet flushes. If you notice any of the fore - mentioned signs, don't wait for the toilet to begin flushing normally. Slow running sewer lines normally get worse with use. Waiting could mean while you are using water in a different part of the house, your sewer is backing up in the basement or wherever the lowest point of drainage in your house is.
If you don't notice any of the above mentioned signs, your situation is not as bad as you may think.
You may be able to resolve a slow flushing toilet yourself.
Remove the tank lid and look for a stain created by normal water level on the side wall of the inside of the toilet tank. If the water level is lower than the staining, the flapper on the flush valve may not be creating a perfect seal. Energy and resource conservation studies have revealed a need for at least 1.6 gallons per flush for a toilet to effectively flush waste out of a toilet and provide enough flow in the sewer to disperse solids. This has become the standard for water consumption for water closets since September 14, 1998. Beware the plumber who advises use of bricks or filled jugs in the toilet tank. Water conservation is already at its lowest point. Using less water to flush the toilet only creates the potential for main sewer line backups.
If water is at the water line in the toilet tank, there may be a restriction in the main jet at the bottom of the toilet bowl. Or, calcium and mineral buildup in the jets at the rim of the bowl may be inhibiting the delivery of water to the bowl once the main jet has begun pushing water through the trap. The main jet begins the vortex action which creates a siphoning effect. The jets at the rim allow for the bowl to wash out as well as to supply the bowl with water until the siphoning has finished flushing waste from the toilet to the sewer.
Cleaning the jets can be accomplished by using a calcium and lime removing solution like CLR or a home made solution of baking soda and vinegar. Here is what you can do...
(If you use CLR, be sure to place plastic wrap over the bowl and the overflow tube. Tape the plastic wrap to ensure fumes do not escape. Also, CLR and Vinegar is very bad for septic system households. If this is the case. You may decide to take your chances with chemicals. However, you may also try to clear the jets beneath the toilet rim with a piece of mechanical wire. You will need a small mirror in order to see where the jets are.)
Watch the following video. The method is said to speed up a slow flushing toilet.
Another reason for a slow flushing toilet is you may have an obstruction in the trap of the toilet or in the bend under the toilet. A toilet auger may need to be purchased but first, try plunging. If that does not work, use an auger. Be careful with the auger. If you place too much pressure on the trap, it could create a leak in your toilet. If you are not comfortable, call a sewer and drain cleaner in your area.
One last reason your toilet drains slowly is there is an obstruction in the vent. The sewer vent allows for air to enter the sewer system. If air can not get into the drain lines, water will not flow and your toilet will not flush. (See this article for more information)
Diagnosing and fixing the drainage problem for a sink, shower or tube may be a long and difficult process. Be safe. If fixing the issue is something that is risky or not being understood, contact a drain service company. The range of pricing for a company who cares to do the job correctly is within $145.00 - $225.00. This depends on material used in piping, age of the house which would help the plumber understand the plumbing code that was used in assembling the plumbing system, access to the plumbing and what is assumed to be creating the blockage.