Chemicals

[JFP]

What is CYA and what role does it play? Also what is the proper level?

Also is there a target number/level for chlorine, to accomplish a good shock?

[Backglass]

What is CYA and what role does it play? Also what is the proper level?

CYA = Cyanuric Acid, also known as Stabilizer. Sunlight degrades chlorine very fast. Without any CYA a pool can go from 10ppm of chlorine to zero in just a few hours. Think of it as sunscreen for chlorine. The target range is 30-50. Anything over 50 and you start having to maintain much higher chlorine levels to get anything done. Get over 100 and you start risking "chlorine lock" where even with high levels of chlorine it wont sanitize.

CYA is in all chlorine products that say "stabilized" like pucks, most pool shocks, etc. The only way to reduce CYA is through dilution...draining some water and refiling with fresh. To raise CYA you can purchase some or slowly raise it through pucks, etc.

Click for the Cyanuric Acid Wiki

Also is there a target number/level for chlorine, to accomplish a good shock

Again this all depends on your CYA level. A normal pool chlorine level is 3ppm and with a level of 10 or so to adequately shock the water. A pool with high CYA levels will require much more chlorine (25+) just to do the same thing.