Moved into the house little over 2 years ago. The neutralizing system was replaced because it didn't pass inspection and previous owner didn't maintain. The water company people said to have them replace the mixture inside the nuetralizing tank every 1.5-2 years. You can see it is about 1/2 filled in the 1st pic. So, here are my questions. 1. Is it time to replace the mixture in the tank even though it is half full? 2. Is this something I can do on my own? 3. Where can I get the mixture? Local hardware store? 4. Can I just fill to the top with new mixture or do I need to empty the tank first?