I can't find the instructions that came with the tar top I bought for my 70, it is low on fluid, when you first fill it up I recall using a chemical, which I still have some left. But at this point do you use the chemical stuff still or just distilled water??? Thanks for the advice.

Once it's been given it's initial fill of acid, just "top off" with distilled water.

(Word of warning, don't take the last bit from your wife's ironing table without replacing it!;)