I love love love the baking soda wash. Give it a try and see what you think. It will certainly be less expensive than buying several different soaps. I follow washing my hair with a chamomile tea and extract spray 
If buying soap is really the way you want to go you can find out the details of your water by either calling the city or testing the water yourself. I tested my own water initially because I have a monster tank I use for my research. You can also bring tap water into a local pool shop. Local organic stores tend to be quite helpful in finding appropriate soaps.
I use Dr. Bronners when I ambackpackingand I absolutely love it.
updated by @westcoaster: 07/09/15 06:29:39AM
