so ... if mps is a waste of money ...

[aylad]

I can't comment on the mps, I'm sure Ben or Chem-geek will be along shortly to address that...

BBB shock is simply the addition of chlorine, (most of us use bleach), to an elevated level to kill off all the nasties, including the CC, in the pool. Bleach is $2.54 for the large size generic jug at our WalMart, and how high you need to take your chlorine depends on your CYA level (if you can see the blue links in my sig, check out the "best guess chlorine chart" for info on chlorine levels based on CYA). I use about 4 of the large jugs a week in my 29K gallon pool, so for just over $10 weekly I can keep my pool crystal clear. If you stay on top of your testing and chlorine, there's rarely a need to shock the pool. You do need to be concerned about your copper heater no matter what form of chlorine you're using--but it's not the chlorine that's the problem, it's the pH below 7.0 that will dissolve the copper into your pool water and create problems. Bleach doesn't change your pH.

[waterbear]

I think the overlooked point here is that a properly maintained pool rarely needs shocking, be it with chlorine or MPS.
Also, I am confused...why do you need to turn off the heater to shock? Shocking does not drop pH and low ph is what damages heat exchangers. Also sulfates (from both MPS and dry acid) can accelerate metal corrosion and there is some evidence they are damaging to plaster.

[Berggy]

I had always wondered why the warning about chlorine and copper heaters ... I always thought it made sense that the PH is above 7.0 what should it matter? But I'm an electrical/mechanical engineer ... and weak in chemistry and was not sure about what effect the chlorine had. If it is no issue then I wont worry about it.

I've been questioning everything lately ... It started innocently enough with why am I paying $2/lb for PH up when I could be paying $1/lb on line and $0.5/lb at walmart grocery aisle?

I shock a lot the first 3 days of the season and once at the end of the season and nearly never during the season anyway. This year they sold me 12% liquid instead of the usual crystal shock ... which made wonder about walmart bleach .... which led me here ... I like it here.

I run 30-40ppm of CYA with 0.5-1.0ppm of chlorine and G25 Nature-2. I use just under 14 lbs (just under 21 pounds? ... cant remember ... its 7 pound containers and I buy 2 or 3 a year) of chlorine in the New Water Cycler PAC 400 feeder per year.

This weekend I looked into walmart bleach ... it is $2.5-ish for 6% @ 1.5-ish gallon containers. So now I'm thinking about the $80 I spend on nature2/year and wondering if I need a salt pool or an automatic drip for bleach system.

My brain hurts.