Re: Phosphoric acid & pH
Phosporic acid is a mild acid but the main reason that is probably didn't affect your pH is that is was neutralized by the calcium carbonate 'efflouressence' that it dissolved which is mildly alkaline. Therefore the water that washed into the pool probably had some calcium and some phosphates in it but was near a neutral pH.
11.75'x23.75' kidney 6.5K gal IG fiberglass pool/300 gal acrylic spillover spa combo; Aqualogic automation/SWCG; Pentair Clean and Clear 150 cart filter; 1.5 hp uprated 2 spd Pentair Whisperflo pump; PF:17
Retired pool store and commercial pool maintenance guy.