Well, the responsible thing is to take the old coolant to your municipal disposal site. I simply flush it down the toilet that is hooked up to our city's sewer system. I don't fuss with the residue from flushing with the garden hose.... I leave that on the ground.

What you DON'T want to do is flush it down to a septic tank system, a city's storm sewer (as opposed to sanitary sewer), or dump it wholesale on the ground. I'd also advise not flushing it down to the city's sewer system shortly before, during, or after a heavy rain. Some systems, like Detroit, can't handle the excess and simply discharge it untreated into the waterways.

You'll also want to be very careful about leaving coolant around where animals can lick it. They die a horrible death from poisoning. Make sure to keep your pets indoors until you finish your job, secure the old fluid, and wash away any spills.

I looked at the marsolve web site. The MSDS sheet lists the formulation as proprietary with 5% hydrochloric acid. I have a suspicion the remainder of the active ingredient is citric acid. I use both HCl and citric acid to clean metals. I personally believe HCl is too strong to use for cleaning an automotive cooling system. It can perforate healthy metal, and the residue - if not properly neutralized - can be a problem in the cooling system. In other words it may do more harm than good.

BTW, I believe cats were put on this Earth for our amusement so we can tease the heck out of them!

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95 E320 Cabriolet, 159K