Another possibility is that it’s not coming from any where but it’s just discoloration in the bowl itself. Perhaps whatever chemicals are being used to clean it, make the bowl look whiter, but once the chemicals/water dries the water appears yellow again.
The water tank used to have some reddish slime that I have cleaned quite thoroughly and kept clean. Also the only cleaner I use regularly in the toilet is baking soda…so that’s not the problem either.
Snaking it is then. Will let you guys know how it went.
what is the chemistry of your water?
if you had iron in water it can give both red and yellow coloration. organisms that live in water can produce slimes and odor. bacteria can grow in iron rich water. this is just an example of what can happen in water.
I have my doubt it is the leaky flapper valve. It could be leaking, but that isn’t the problem. Look in the tank. Is it yellow and smelly? If not, leaking into the bowl shouldn’t cause the problem.
If you let a pan of water set out, does it yellow like the bowl? If not, it isn’t the water.
I can’t say what, but somehow something must be getting into the bowl.
I have my doubts about the tank leaking be the problem as well, but don’t forget, it’s not just water sitting out, it’s water sitting out that’s then coming through the toilet rim where urine has been splashing around.
Also, checking for a leaky flapper valve is SOOOOO easy. Far easier then snaking the drain system.
And with that, the OP mentioned getting out the snake. If this really is caused by something further down the line backing up into the toilet, the problem is likely to be further down the line then what a toilet snake can reach. A toilet snake gives you, what, 4 feet or so, and most of that is used up before you even reach the main part of the drain. This is something that’ll need to be done from a clean-out somewhere along the basement ceiling.