At least I think I've thought this out. During a discussion yesterday in another thread, I mentioned I use a mineral pack. I've used one for 13 years and this year decided to make a run without it. In conjunction with it, I used monopersulfate. My wife is a bookkeeper through and through, so as you might imagine we track every penny i spend on the pool right down to a $1.00 O-ring. The reason I mention this is because I also use a spread sheet to track every measurement of chemicals, addition of any chemicals, weather conditions, pool use, etc. daily. Hey, I'm retired and I find it fun.
So here's my observation: This year I started without a mineral pack and no monopersulfate. Just good old chlorine bleach. I found I was using an average of 76oz of 8.25% bleach a day at .024 cents an ounce. I buy 3 121oz bottles at COSTCO for $9 and some change. My season last year was 122 days long. At .024 cents an ounce that is $222.52 in chlorine for the season. Not bad, really, except some folks would find it inconvenient to carry 75 bottles of bleach home.
Checking my spread sheet last year, here's how it stacked up: I spent $98 on monopersulfate, generally putting in 2lbs a week at $3.50/lb. Some weeks I only used one pound and quite a few times, based on measurements, I went longer than a week. Keep in mind I check everyday, which wouldn't be possible for everyone. I also spent $90 on a mineral cartridge and an additional $32 on bleach. The total is $220.00. So close to just using bleach that it is scary. Just the convenience of not having to go out and buy bleach every couple of weeks and having everything delivered to the house is nice. But, here's my real finding...
I found when using the mineral pack and MPS, I only need to use 20oz of bleach a day as compared to 76oz without using the combo, keeping the FC at the exact same level.
I am aware that the copper in the mineral packs could cause some staining. I have a black plaster pool and because of that, I may not be able to see any mild staining. The next warning I always hear is that if you ave blonde hair, it may take on a green tint. My daughter is a natural blonde and after swimming in the pool almost her entire life this hasn't occurred.
So for me the combination of mineral pack and monopersulfate hasn't proven to be any more expensive or damaging to the pool or swimmers. It has proven to be a little more convenient. Is there any other reason for me to abandon the combination?
Thanks for considering this.