I am new to the forum. And new to using forum all together. So I hope this question is in the right place. It may need to be in "The Deep End". I think this pool site is the best around. :-D I was wanting to know if Arm and Hammer Super Washing Soda and regular soda ash should have the same by weight or by volume as each other in the pool calculator? I am sure the pool calculator is right, but this "All about hand dying T-shirts" website has got me a little confused. Link Sorry, if the link did not work. I will repost it, if needed. The paragraphs in the web page titled Hydration and Where can you buy soda ash?, is where my question comes from. I know that I will get the right answer here. Thanks to all for the great info on the TFP site.