Before beginning, prepare your workspace and yourself. Put on a pair of waterproof protective gloves and safety glasses to shield against splashes. Open a window or activate the bathroom's exhaust fan to ensure proper air circulation, which is especially important if you decide to use chemical cleaners later.

To allow cleaners to work directly on the stains, you must remove the water from the bowl. First, locate the toilet's water shutoff valve on the wall behind the toilet and turn it clockwise until it stops. Flush the toilet once to drain the water from the tank and lower the level in the bowl. Force the remaining standing water out of the bowl by making several vigorous thrusts with a plunger. Alternatively, you can use a large sponge and a bucket to soak up and remove the last bit of water.

With the bowl empty, pour a generous amount of distilled white vinegar directly onto the stained areas. Ensure the vinegar completely covers the hard water rings and any discoloration at the bottom. The acidic nature of vinegar is effective at dissolving the mineral deposits (calcium and magnesium) that cause the stains.

Allow the vinegar to sit in the bowl and work on the stains for at least 4 hours. For severe, long-standing stains, leaving the vinegar to soak overnight will yield the best results. Close the toilet lid during this time to minimize the vinegar smell and prevent evaporation. Do not flush the toilet during the soaking period.

After the soaking period, take a stiff-bristled toilet brush and begin to scrub the stained areas. The vinegar should have significantly softened the mineral scale, allowing you to scrub it away. Apply firm pressure and focus on the waterline ring and any patches at the bottom of the bowl.

For any remaining stubborn stains, a pumice scouring stick is the most effective tool. It is critical that you wet both the pumice stick and the porcelain surface before you begin scrubbing. Dip the stick in the remaining vinegar or under a faucet. Gently rub the wet stone directly on the stain using a back-and-forth motion. The abrasive nature of the pumice will grind away the mineral deposit without scratching the porcelain, as long as both surfaces are kept wet.

Once you are satisfied that the stains are removed, turn the water shutoff valve counter-clockwise to restore the water supply to the toilet. Allow the tank to fill completely. Flush the toilet two or three times to thoroughly rinse away all vinegar, loosened sediment, and any pumice particles. Inspect the clean bowl.