A friend called me complaining about calcium deposits in the toilet bowl. I told him take a toilet plunger and remove most of the water in the bowl and to pour a half cup of pool acid into the bowl and let it sit over night then flush it 4 or 5 times to remove any acid in the lines. He goes to purchase the pool acid and they asked him what he was going to do with it and they told them they do not recommend that anymore because it is harmful to the environment. I should have known better but that is the way we used to do it. Gotta get on the ball.

We swim in pool water mixed with muriatic acid, and it NOT "harmful" to OUR environment.

Tell him to get some CLR. I'd worry about using strong concentrations of cyanuric acid, but not for environmental reasons. If it etches the glazing on the bowl, you'll never keep it clean.

i have an old eljer toilet out back that has not been used much. it had some calcium deposits in it.
i got some lysol toilet bowl cleaner for calcium. bailed out the water in the bowl and poured the whole bottle down the overflow. it came out around the rim and out the little hole. i smushed it around, closed the lid and left it overnight. the toilet liiks brand new. cost 2.00 at the supermarket.
my motto.. never use a little when you can use alot..