I'm pursuing cleaning a spa tub that keeps spitting out black and white
greasy- soapy chunks (I call 'em old-people chunks, based on the folks
I bought the house from), and a local spa shop recc'ed some 'super
concentrated chlorine', a teaspoon in 110 gallons supposedly kicks
grime's butt. It is sold primarily as a sanitizer. I joked (1/2 anyway)
about dumping half the thing in my tub and they said the fumes would
probably kill me.
This stuff (its granular) carries a warning about getting it damp-
it'll catch fire if it gets moist. That's how you can tell its the good
stuff, I guess.
Haven't tried it yet, or I'd give you an evaluation.