I really don't think you need to. I've never dechlorinated my snakes water.
But, if you really want to you could add a reverse osmosis filter or an activated carbon filter directly to your sink. Than attach a hose to fill your bucket or tub or whatever means you will carry water to the enclsoure. The hose may even reach the enclosure depending on locations if sink and enclosure.
You could also use dechlorinating agents found at pet stores. I use them for my fish, but not my snakes.
The third option would be to let the chlorine evaporate in a tub or bucket. This will take anywhere from 24-48 hours though, depending on chlorine levels in the water and how big the quantity of water is. You'll have to store the water uncovered somewhere it will stay clean though.
But any which way, I'll be watching this build and possibly "borrwing" some ideas from you. I'm looking forward to seeing your progress. Rainbow is lucky to have such a hard working and dedicated keeper!