I'm in the process of repairing a neighbor's soda ash injection system. She had neglected adding the soda ash/bleach mixture for several years and her fittings (the whole house is copper) are starting to show a lot of green/corrosion from the acidity... The injection point was so deteriorated that it became clogged and the pump couldn't add the solution even after the tank was filled.

My question is about the LOCATION of the injection. I'm repairing a lot of the damaged fittings and pipe, but it occurred to me that it makes the MOST sense to inject the solution as far upstream as possible to minimize the piping exposed to the acidic water. I've attached a sketch showing the complete system and where the ash is (was) being injected, and where I would like to inject it. Can anyone see a reason NOT to do this relocation? Any comments regarding the original location would also be appreciated (was this a poor spot to begin with?).

Thank you so much for any and all input.