I've recently renovated our bathroom and I changed the drain pipe leadin from the toilet to ABS but kept the old toilet. I now here a dripping sound from inside the toilet whenever the water level rises (waste has been deposited into it). I'm wondering if this is normal and I just never heard it before cause the drain pipe used to be in cast iron or is there a problem? There is a little water around the toilet but I think that's related to a broken washer linking the tank and bowl.
The toilet bowl is typically full when you start your business, so yes, whenever you add something, some water goes down the drain. The abs pipe is MUCH noisier than CI, so that's probably it.
Fix the leak, or you'll end up replacing the rotten floor.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013