Thank you for all of the advice. I may start another thread about CYA struggles and recommendations. That is going to be a journey in and of itself - not just to reduce CYA but to keep it at manageable levels indefinitely.
If you follow the
TFPC Method of pool care, it will be a short journey to perfect water!
As far as the CH goes, 250 would be the minimum recommended specifically for a tiled pool? It seems sometimes I come across recommendations of 150-250 with 250 being the very upper limit. It just seems like the recommendations for CH are very broad and all over the place. Does higher CH have an adverse impact on any other measured requirement? Like if you keep CH above 250, you should also keep pH a little low/high or TA a little low/high, etc.
Calcium hardness does NOT affect other chemistry specifically. Even though pool stores and pool "experts" will make wild claims that things like TDS or CH affect chlorine, the truth and science says otherwise. So, in general, CH can have a large range. You want a minimum amount of calcium in the water to protect your tile grout. Grout is composed of cement which is a calcium based material. So if your water has low calcium hardness then it can strip the calcium out of the grout and weaken it. And this leads to an important topic about the relationship of CH to TA, pH, etc - the
Calcium Saturation Index or CSI.
The CSI is the measure of how saturated your water is with calcium carbonate (the primary form of calcium hardness in water). If the CSI is 0, then your water is perfectly saturated with calcium carbonate. If your CSI is positive, then your water is over-saturated with calcium carbonate and there is a driving force for that calcium to come out of solution either by causing cloudiness or by actually scaling out on the tile as calcium deposits. If you CSI is negative, the your water is under-saturated with calcium which mean there's a driving force for the water to absorb calcium either by etching or leeching calcium out of the pool materials.
The important thing to remember is that the CSI is a thermodynamic quantity which simply tells you that a driving force exists. It does not tell you when or how fast either scaling or etching will occur. Typically speaking, if the CSI is between -0.3 < CSI < +0.3, then we say the water is balanced. If you go beyond those limits, then there's the "potential" for scaling (CSI > + 0.3) or etching (CSI < -0.3) to occur. If your go beyond +/-0.6, then your water's CSI is really not good and you're very likely to scale or etch.
PoolMath is your friend! If you add in all your water parameters (using a good test kit like your K-2006), then PoolMath will calculate your CSI for you. For your grouted & tiled pool, I would aim for a slightly negative CSI, somewhere between 0 and -0.2 would be just fine.