A toilet that flushes slow and gurgles, instead of flushing vigorously, can be caused by one of several problems. Some causes of a slowly draining toilet bowl can be solved with little cost and time investment. The more expensive fixes still cost less than a single visit from the plumber.
Before you begin trying to solve the problem of the toilet draining slowly, test the cause of the problem using a bucket of water. Fill a five gallon bucket with water, and then pour the bucket rapidly down the drain hole in the bottom of the toilet bowl. If the toilet flushes without any problems, then the problem is not enough water reaching the bowl. If the toilet still struggles to flush, the toilet's drain is clogged and you must remove the clog.
Once you have determined, using the bucket test, that the toilet's drain has a clog, try the easiest methods of unclogging the toilet first. If the bowl has little to no water standing, pour baking soda and then vinegar down the toilet's drain opening. You must wait at least five minutes for the mixture to eat away at the clog, and then try flushing the toilet again. If the clog remains, try pressing a plunger over the drain opening and pumping the plunger's handle a dozen times. If nothing else works, feed an auger into the drain so it pushes through the clog.
The toilet bowl's ports sit just below the rim, where they are spaced every few inches. Hard water deposits will collect in the toilet's ports as the water exits the tank and enters the bowl through the ports. Clear the ports using a wood skewer or a wire clothes hanger. If the toilet still flushes sluggishly, mix one part muriatic acid with ten parts water in a bucket. Pour half of the bucket down the overflow tube located inside the toilet's tank, wait half an hour and then pour the rest of the bucket down the overflow tube.
The toilet's flushing power can diminish when a cleaning tab you drop into the toilet's tank dissolves to the size that it can be sucked down the tank's drain. The cleaning tab is not small enough to pass through the ports into the bowl like the water, and instead it clogs one or more ports. The cleaning tab will sit in the toilet bowl, clogging the ports, until it dissolves or you break it up using a wood skewer or a wire hanger.
A sluggish toilet and its gurgling sounds also may be due to a partially or completely clogged toilet vent pipe on the roof of the house. If you are not comfortable climbing onto the roof and clearing out the vent pipe, hire a plumber to do it for you.