bert , I just treated 2 tanks.....I bought a quart direct from the POR15 outlet on ebay for like 42 shipped....I used muriatic acid to clean the tank, rinsed it and treated it with phosphoric acid to etch the metal, rinsed it out with boiling water, and then stuck them in a 250degree oven for 15 mins to dry it completely (thats one of the most important things)..you can use a heat gun or hair dryer if the tank isnt removeable...then I used a old plastic cup to pour the stuff and resealed the can immediately. I treated one tank and dumped it directly into the other...then treated it....i put them on top of a old bown with the petcock down to drain. 70% of it drains back out and is wasted. a half pint can would have been plenty....i let it sit inside my music room for 4 days to dry......it looks awesome...its like a rock hard thin coat of metallic silver paint..Ive yet to fill the tanks yet. but im sure they will be fine..I used maybe 1/4 to 1/3 of the quart, but I have several more tanks to treat.anyway, hope that helped......