I have a 40,000 gallon pool. I drain it to 2/3ds in the fall and let it refill with rain/snow. For the past 5 years I have had CYA levels way high (by memory I think around 100). Before that it wasn't tested for cya. Right after I learned of the cya overdose I switched to calcium hypochlorite shock from triclor. It didn't help much. So I switched to calcium hypo tablets in the chlorinator and tricolor shock. This helped and the levels are dropping but not as fast as I would like. It seems to me all available tricolor must have massive amounts of cya in it. Its been a year since I added any tricolor and the CYA level is still over 40. Pool stores tell me to drain it to 1/3, refill and test again, if still high, drain 1/3d again, etc. Doing that with a 40,000 gallon pool several times a year to deal with overloaded cya is kind of expensive and a lengthy process. It gets 1/3d fresh water yearly anyway. I did not know about the various warnings like explosions and dissolve problems (the calcium hypo I've used dissolves fine in the chlorinator). I asked an engineer at pentair why they disallow calcium hypochlorite in their feeders. He stopped responding when I asked that question. My question involves putting calcium hypo in a standard chlorinator. Is the explosion risk from direct contact of calcium and sodium chemicals? Has anyone else tried calcium hypo tabs in a standard feeder? At this point my feeder is acclimatized to calcium tabs. If I can get the levels down this year my plan was to maintain cya at the low end of recommended with tricolor shock and continue with calcium tabs in the feeder. Comments?