@Mrs. K -
I've been doing water glassing for ~6 years. I do discard the lime water down the drain without issue. I make sure to run the water for a while afterwards to insure the lime is fully dissolved (as opposed to partially settling when water glassing) and doesn't clog the U-pipe under the sink.
Disposing in the toilet is basically the same as in the sink. They all end up going out the same pipes. I would flush multiple times to insure there is enough water to keep the lime from settling and caking in the pipes.
@WingItRanch -
I'm connected to a sewer system and not septic. Not sure if the lime would create any issues there.
The lime we use has multiple names: hydrated lime, pickling lime,
agricultural lime, etc. So, I'm sure the lime *can* work in compost, but I'm not sure about the volume of lime to the volume of compost/soil you are producing. The theoretical downside is that too much lime would raise the pH too much and cause problems for the various bacteria/insects/worms/etc that are trying to break it down. I'd try dumping it in one section of the compost and see if it breaks down as well as the rest.
I do dispose of my water glassed egg shells in the compost, since I'm not 100% certain I can give it directly to the chickens.
----
Some good questions: If you haven't already seen it, we have a
master thread on water glassing that discusses the basics and answers many other questions.