On Wednesday, March 14, 2018 at 9:57:36 PM UTC-7, wrote:
I use pool muriatic acid it's little hard to handle so make sure you wear chemical goggles and chemical gloves go up to your elbows. Get a hose with a nozzle on it keep it handy in case you get it on your skin you can flush it fast it burns like anything not going to melt you to the bone just leave red mark. The only place you should be really careful is your eyes that's why you want the goggles like you ware in chemistry class. Another thing is hold your breath when your pouring it on a spot then step back let it work for awhile. I also mix it 50/50 in a 1 gallon bug sprayer with some dawn dish soap that is easier then pouring it lot less comes out. Once I get everything clean I fill up the tank with a gallon of pool acid let it cook for an hour. Then I add water open the drain let it drain out make sure the drain isn't going on concrete it will etch it. It's the only thing I found that can break down really thick scale my drain pump broke I used the cooler for 2 seasons without doing much but running a quart of cooler cleaner each season this year I replaced the pad and had to clean everything was so thick with build up. The de-etch stuff they sell for coolers hardly make a dent only pool acid is strong enough to break down 1/4 inch of calcium. You can use scrapers and wire brushes but then you will scuff up the paint it will rust I didn't want to do that. When you need to really clean like this best to remove the pads so you can get to everything easier. You can run pool acid in the pads but if it's really bad just replace the pads not worth the hassle.