Ok, so maybe it's not quite as bad as my title.
Here's some background:
My wife and I recently acquired a foreclosed home with a neglected pool. We are first time pool owners and briefly considered draining it, but were dissuaded by my brother in law who threatened damage to the liner. I followed his (in hindsight very good) advice and spent weeks scooping out leaves, adding liquid chlorine, vacuuming to waste, running the filter 24/7, and backwashing often. Through persistence and dumb luck, I managed to clear out the pool and balance the chemistry without adding anything too stupid to the water on the recommendation of local pool stores (unless you consider a bottle of floc and overpriced baking soda stupid). I'm now the proud owner of a sparkling blue pool!
When the surface is still, I can barely tell there's water in there! 
It wasn't until I was nearing the end of this ordeal that I discovered TFP, and it really helped me tie the loose ends together. The pool calculator has been invaluable, despite my not having 100% reliable inputs...
Which brings me to my current dilemma... How do I convince my wife we need to spend another $50+ on a test kit!?
Our water is practically invisible and my wife scoffs at the idea of needing to put out that much money just to keep it like that... Especially not on the recommendation of "those strangers on the internet who want you to add bleach to the pool" 
I've pulled out every argument I can think of, from the "appeal to reason" (failed miserably), to the "appeal to independence from pool store tyranny" (also failed), to the usually-bulletproof "what about the children!?" (close, but nocigar K-2006).
I realize that is probably an unanswerable question, so I have a more concrete question for you. How would YOU maintain a pool in the absence of a reliable test kit? And more specifically/technically, does anyone know of a way to derive a CYA measurement from other inputs (FC loss over time, temp., sun exposure, etc)? I realize knowing exactly what's in your water is the cornerstone of the TFP method, but is a CYA and FAS-DPD test kit the ONLY way to determine those numbers?
She has been singing my praises to friends and family about the state of our pool, so I suspect she will eventually give in, but I also suspect it will only be after we have an "incident" where the water turns green or the kids get an ear infection...
Help me TFP, you're my only hope!
Here's some background:
My wife and I recently acquired a foreclosed home with a neglected pool. We are first time pool owners and briefly considered draining it, but were dissuaded by my brother in law who threatened damage to the liner. I followed his (in hindsight very good) advice and spent weeks scooping out leaves, adding liquid chlorine, vacuuming to waste, running the filter 24/7, and backwashing often. Through persistence and dumb luck, I managed to clear out the pool and balance the chemistry without adding anything too stupid to the water on the recommendation of local pool stores (unless you consider a bottle of floc and overpriced baking soda stupid). I'm now the proud owner of a sparkling blue pool!

It wasn't until I was nearing the end of this ordeal that I discovered TFP, and it really helped me tie the loose ends together. The pool calculator has been invaluable, despite my not having 100% reliable inputs...
Which brings me to my current dilemma... How do I convince my wife we need to spend another $50+ on a test kit!?
I've pulled out every argument I can think of, from the "appeal to reason" (failed miserably), to the "appeal to independence from pool store tyranny" (also failed), to the usually-bulletproof "what about the children!?" (close, but no
I realize that is probably an unanswerable question, so I have a more concrete question for you. How would YOU maintain a pool in the absence of a reliable test kit? And more specifically/technically, does anyone know of a way to derive a CYA measurement from other inputs (FC loss over time, temp., sun exposure, etc)? I realize knowing exactly what's in your water is the cornerstone of the TFP method, but is a CYA and FAS-DPD test kit the ONLY way to determine those numbers?
She has been singing my praises to friends and family about the state of our pool, so I suspect she will eventually give in, but I also suspect it will only be after we have an "incident" where the water turns green or the kids get an ear infection...
Help me TFP, you're my only hope!