Use a dry tool to spread the grease. One can use a small cloth or a rag also. Once the part of flapper gets greased, one can apply it on the edge of the siphon hole in the tank also. It will give a protecting cover to the tank so that to avoid leakage in the future.
You don't want to use petroleum jelly because a petroleum based product could degrade the rubber flapper and/or the rubber gaskets. Just clean the flapper and where it seats real well.
Adjust the chain length so that the flapper closes fully after flushing. Use a Flapper with a Higher Quality Material: Consider upgrading to a flapper made of a more durable material, such as silicone or rubber designed for longer life, which can help reduce leaks.
The most common issue with toilets randomly flushing is that the flapper has become brittle or sediment has formed on the flapper/tank which prevents the flapper making a complete seal. This will allow water to slowly drip from the tank into the bowl.
The reason the flush valve/flapper is getting stuck up is it's binding against the float rod. Either bend the float rod a little bit to give it some clearance or rotate the fill valve slightly to move the rod towards the back of the tank.
Moving a float (a float is placed on the flapper chain) up the chain, so you are setting the flapper to close faster. By lowering the float on the chain you are causing the flapper to stay open longer.
If the excess chain hangs too far, it can fall between the toilet flapper and the toilet valve. Thus, it creates an opening, never allowing the flapper to seal the valve fully. The fix is to use a wire cutter or side-cutting pliers to trim off the excess chain.
Check that the flapper is correctly aligned with the flush valve seat. Ensure the flapper's ears or pegs are securely attached to the overflow tube or flush valve. Verify that the flapper moves freely and sits flat against the valve seat when closed.
Check refill tube first: If refill tube is inserted too far into the overflow pipe, pull it out and reattach to outside of overflow pipe. This should keep the tube from entering the overflow pipe and often stop an internal leak from the tank to bowl and prevent “ghost flushing”.
The easiest way to test for a bad flapper is to drop some dye tablets into the tank and then check to see if the dye moves into the bowl.
If you've replaced the flapper and adjusted the float ball, but the toilet continues to run, the most likely cause is a leaking flush valve. Usually, such a leak is around the mouth of the flush valve where the flapper is supposed to make a good seal.
Toilet flappers usually last for about 3 to 5 years, but the lifespan can vary depending on factors such as the quality of the flapper, the water quality, and the frequency of use.
Vaseline. Though not as harmful as grease, Vaseline (petroleum jelly) is a viscous solution that can and will cause clogs.
Gently lift the flapper and scrub it with an old toothbrush or scouring pad. Scrub the seat assembly as well. Turn the water back on and test your work. If cleaning doesn't fix the leak or the flapper is physically damaged, you need to replace it.
But there's hope for our poor little flapper in the form of Vaseline, which can partially restore its youth and suppleness. Drain the toilet tank. Dry off the toilet flapper. Rub Vaseline on the flapper and its connecting washer until they soften.
Improperly Installed Flapper: If you have the correct flapper installed and it is adjustable, you may need to tweak the settings to get the flapper to close faster or slower. Flapper Chain Misalignment: If the flapper chain has too much slack or is too tight, it can cause it to remain open for too long.
The most common toilet leak is caused by a deteriorated flush valve (flapper) at the bottom of the toilet tank. If the flapper does not seat properly, water will leak into the toilet bowl. Often this leak will occur without being heard.
This problem is almost certainly caused by a bad flapper or flapper seat. The solution is to drain the tank and bowl, check and clean the flapper seat and then replace the flapper if it's worn or damaged.
A leaky flapper doesn't reseal properly after the toilet has been flushed. If your flapper is worn, broken or damaged, replacing the unit should help your toilet function normally. If the flapper looks to be in good shape, check to see if it is aligned with the opening.
Check your water levels
Low water levels in your tank are common causes of toilets filling up with water when flushed. They can also cause slow-draining toilets. You can manually top up your tank with water to help the flush. Then, check the flush tube for cracks and bends that lead to leaks.