My CYA level was measured about three times recently at 150ppm. I use a Rainbow test kit to measure FC, TA, CC, and PH, but don't have the reagent for CYA. I've been depending on the two pool stores where I buy my DE, Muriatic Acid, and Trichlor tabs. I don't entirely trust either of them, but to their credit heir numbers and mine are pretty close. To their credit, nether has tried to sell me "snakeoil" products.
The last set of numbers were:
Total dissolved solids 500ppm
Based on this I need to drain more than half my water. I've been waiting for some cooler, overcast weather and even rain, to keep the plaster from getting dried out. However, the person at one of the store told me I also need to pressure wash the pool. This is an additional complication because now this task is not feasible as an overnight activity.
I have read the articles on how CYA harms plaster and intend to accomplish this as soon as I get my pump fixed. (That's another story) So what is the deal on pressure washing? I'll drain the whole pool if it will save me this task. I am not looking forward to getting into the remaining water to accomplish this.