How to remove water spots from ice chamber in bong?

Question

I have these small water spots stained into the ice chamber of my bong. I have tried using alcohol and salt, dish soap, and a thorough scrub. No of these seem to work. Any suggestions would be great?

Answer 1

Items that use water regularly get a build up of Lime.  Try soaking it in vinegar to loosen the 'lime' and then wash as before.  

Answer 2

Try hydrochloric acid.

Answer 3

Ammonia should do it, you may have to let it sit for a while then agitate for a bit more.  Rinse thoroughly, and let it dry out before using.