I live in an apartment building with a toilet that is more than thirty years old. For the past few days, I've noticed hissing sounds and occasional dripping sounds coming from the toilet tank which I've been able to eliminate by lifting the float ball manually by a fraction of an inch in which case the sounds have ceased immediately. However, when I do this, by propping up the float ball, all the water in the tank slowly drains (over 15-20 minutes) until the tank is empty. I don't know why the water drains. Nonetheless, I have been able to leave the float ball propped up with no problems, only releasing it to refill the tank when I need to flush this toilet.
Today, however, I hear hissing and dripping sounds even with the float ball propped up and the toilet tank devoid of water.
There is no evidence of water leaking into my apartment.
Is there any danger of water leaking either into the walls or apartments below me?
What might be causing these hissing and dripping sounds?
Is it safe and not likely to exacerbate any problem to wait a week or two before calling my landlord (since it would be difficult for me right now to take time from work while his men are in my apartment)?

It is very possible that your neoprene flapper or the flush ball, which ever you have is not completely stopping the water form going from the tank into the bowl when it is in place. Take the tank lid of off the commode tank and see what you have that the handle lifts when you flush it. Which ever it is replace it and see if this stops the problem. This is a very common problem.

letmetellu may have it or there is another possibility. I think your fill valve, also call a ballcock, is not shutting off completely afetr the fill. The hiss is water under pressure getting past the seal. The drip would be excess water dripping down the overflow pipe. Is the level of your tank water stying one inch below the top of the over flow pipe? Which fill valve do you have https://www.askmehelpdesk.com/attach...-ballcocks.jpg

In reply to ballengerb1, the tank water, when full after flushing, remains comfortably below the overflow pipe.
Please note that, when devoid of water, the hissing and dripping sounds from the tank, noted earlier today, seem to have stopped.
These will no doubt return, however, if I allow the tank to refill.

In reply to letmetellu, you may or may not be correct. I understand that I can test your hypothesis by adding some food coloring to the tank to see if it traverses to the bowl over the course of a few hours.

My immediate concern relates to whether there is risk from water causing property damage (see my original question). Is the water safely contained within the toilet and pipes?
Too, I'm curious why propping up the float ball causes the water to drain from the tank.

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I'm curious why propping up the float ball causes the water to drain from the tank.

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So am I. Take your finger and run it around the flat side of the flapper. If you feel any wavy or rough edges replace the flapper. ( If it's losing water I'd replace it anyway).
As for that hissing ballcock let me know which ballcock is yours (see images) Back to you, Tom

Reply to Tom (speedball1):

#1 in the image to the right.
I suspect that the flapper needs to be replaced.
Again, however, I'm concerned about potential damage. (If I hear dripping but don't see any, where is the water going?)
Thanks.

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I'm concerned about potential damage. (If I hear dripping but don't see any, where is the water going?)

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Which is why you weere asked to check the flapper. ( Have you done so?) If the flapper were dripping the drip would go down in the toilet bowl. So it wouldn't be seen. DO IT!
As for the hissing, open up the lid and flush the toilet. Do you see any water squirting out? Let me know, Tom