Finding & Fixing Toilet Leaks: A Handy Guide For Your Convenience

If you find water on your bathroom floor, look for most common causes before you start to panic.

How to start looking for the causes of toilet leaks?


Tank sweating can be one of the common causes. This mostly occurs due to the difference in the temperature of the water inside the tank, which is generally cold and the temperature of the air outside the tank in the bathroom, which is very often warm and steamy. Most of the plumbers This causes the vapors present in the air in the bathroom to condense when they come in touch with the cold surface of the tank. This may drip and show as water on the surface.

Still, if you are not sure, wipe the outside of the tank with a towel and wipe absolutely dry. Now, watch visually if the tank’s outer surface is gathering droplets of water that tend to slowly drip on the floor.


You can use toilet tank liners or anti-sweat toilet tanks that mix cold and warm water coming into the tank.

Leakage from inside the tank

Once you are sure that condensation is not the cause, then next step to begin would be to check the tank for any kind of leakage.

Remove the lid of the tank carefully, and add any food coloring to the tank water. Do not flush the toilet, and wait for the color to mix and settle down. After 10 to 15 minutes, if you find colored water on the floor, it would indicate the leakage from inside. Check for cracks in the porcelain tank, leaks around the bolts and rubber seals, leaks between the tank and the bowl or from the gasket where the flush valve allows water to enter the bowl.


  • If the leaking is between the tank and the bowl, then you need a new tank-to-bowl sponge gasket or new washers or bowl bolts for the tank. It is very difficult to pin point whether you need to change the gasket, washers or bolt sets as all toilet bowls differ in structure. Best would be to change all to be on safer side until you are very sure.
  • Shank gasket is attached to fill valve on the inside of the tank. If there are no cracks in the tank, just tighten the shank nut. If the leak doesn’t stop, then you need to change the shank gasket.
  • When the fitting of the fill valve gets loose, or the rubber seal that keeps the water in tank from draining out gets old, leakage occurs. Replacement is the only option if fill valve stops working.
  • With high regrets, if the tank has any crack, there is no other option than to change the tank.

Other Possibilities

  • If the shut off valve is leaking, try to tighten the valve of the plumbing, else it has to be replaced.
  • Check for any leakage at the nuts on each end of the supply line. Water inlet at fill valve and shut off valve may need replacement of supply washers.
  • If you notice waste water flowing back and seep past the wax ring, a new wax ring may fix the problem. But, if the problem persists, then a blockage in the waste drain line shows higher probability. A professional help can only clear the blockage.

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