Did I miss something? The OP didn't mention TDS, just phosphates. (But I agree: In 99.99% of situations, TDS is irrelevant--once in 10,000 times it's the problem).

The answer is: If you can clean up and maintain your pool then, by definition you don't need to worry about phosphates.

Now I have another question: Is your CYA 25 or is it 100ppm?

If it's 100ppm, you CAN maintain it and swim safely if you keep your FC between 8 and 15ppm--just don't let anyone wear new, designer bathing suits. Otherwise you are fine. I don't like it that high, but I disagree with JohnT that you need to be below 60ppm. aylad maintains her pool consistently at a CYA of 80ppm because chlorine burns off too fast in Louisiana. I personally keep mine between 30 and 50, but if it gets to 60 I merely compensate with my FC level.

The shock level for CYA=100pp is 25ppm of FC--maybe that's what you meant. You'll need to keep the pool there until it's clear. Then maintain it at the 8-15 ppm level.

Or you can drain 50% of the water and refill for a CYA=50.

Where I am, it's not much of an issue as it's been raining all week and a lot of water is coming in and draining off--maybe if it stops pouring tomorrow I can take a proper "snapshot".