Tom G, If you have a pool supply store near you, they will do a ph and alkilinity test for free. If you have reasonable alkilinity, the alum will be buffered to where ph won't be a factor. Alum is not really very acidic and can be mixed in concentration with bare hands and not cause skin irritation (from personal experiance). I feel the lime is always a cheap insurance and can be spead dry either before or after applying the alum (I prefer after) also, I use pond water to make the alum slurry.
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