Callen
Aquarium Advice Freak
I wouldn't do more than 50% water change at a time.
In your circumstances you really need to invest in a rodi unit. No knowing what is in the water you are getting. If they use copper tubing in their process it could be contaminating your tank for instance.
I bought one and had to return it because it had a broken part. Looked around town at lowes, Home Depot, sears and can't find another. Will have to order online.
Should I wait on that before I do the water change?