Re: My KM has some rust...
What you want to do is buy a bottle of rust remover. Its like 3 bucks, i always see them at the auto store. Dont buy the spray, just the bottle. Then use your brush and brush that rust removing liquid in the hookah. After you see that the rust is gone, then rinse it with lemon juice and water, this will remove any smells from the chemical. Then, make sure to dry out the inside of the stem by blowing through it, or taking some paper towel and trying to fish it down there. The purge valve will be a bit harder to clean and dry, but its the same thing.
Remember to remove ALL rust
also remember to completely dry EVERYTHING