There are many reasons for a leak from your toilet tank into the bowl. Before taking any measure to fix the problem, ensure that you troubleshoot the problem and identify the particular spot that is leaking. Place a porous bag with a dye into the water-filled toilet tank and let it diffuse. After half an hour, if you find dyed water in the toilet bowl, then you can be sure that there is a leak in your toilet tank.
If the water turns on the water supply on its own without flushing, then that is another clear indication that your toilet tank has a leak. Below are the possible causes and ways of how to fix them.
Cracked Toilet Tank
If the water-holding tank of your toilet is cracked, it will leak water into your toilet bowl. This problem needs urgency to fix least you find your house flooded. The only way to repair a cracked toilet tank is by replacing the toilet. If you cannot handle the replacement job, get a competent and experienced plumber to do the replacement.
A malfunctioning flapper is the leading cause of the toilet tank leaking water into the bowl. At the bottom of the toilet tank, you will locate the flapper, which provides a watertight seal. When it starts to malfunction, the flapper will not close properly allowing water to leak through the space left and cause a leak.
Wear of the flapper can happen after years of use, and repair or replacement is necessary. Flush the toilet and quickly but carefully remove the flapper. Dry it off and apply a generous amount of the side of the flapper that connects to the bottom of the tank. This will create a watertight seal that ought to fix the problem. If the leak continues, you will have to replace the flapper or get a professional plumber to do it for you.
If the assembly between the tank and the bowl is loose, you will not miss noticing a leak. Tighten any loose nuts and bolts with an adjustable wrench to have a firm assembly. Watch out and avoid tightening too much least the porcelain material used in making the toilet could crack and end up replacing the entire toilet.
Other parts that could be the cause of the leak are the connection of the water supply to the toilets tank. Rectify this problem by tightening the jam nut with a wrench only a quarter-turn past hand tightening to prevent the tank from cracking or the nut from striping.