One Step is a proprietary cleaning (and somewhat sanitizing) solution that is a secret formula; even the Wine Wizard will never know exactly what it’s made out of. From what I can find out, though, it sounds very similar to products I’ve used in my wineries which often go by trade names like Peroxycarb. Essentially, these products are a basic (high pH) powder of sodium percarbonate and sodium carbonate that also releases hydrogen peroxide when water is added. The basic nature of the solution loosens scale and detritus (the cleaning action) and releases hydrogen peroxide, which is a strong oxidizer and disrupts microbial cellular function to such a degree it can repress or kill yeast and bacteria. The makers of One Step and similar products usually will give a recommended concentration and contact time in order to maximize their cell-slaying power. For One Step, it’s 1 tablespoon per gallon (4 L) of water.
One Step claims, by its very name, to be a “one and done” kind of cleaner and sanitizer. From what I can learn about it, it is somewhat pH adjusted with sodium citrate so that it may not be as necessary, in some applications, to rinse with water or acidulated water. I would leave that choice up to you depending on your situation, however. If you can feel a slippery film or residue on your equipment, that’s one of the classic signs of a basic (high pH) environment. Think soap or how a solution of soda ash feels. I would wager that if you’re still feeling a slick film, you may have residual product on your surface. Because of that, I would be hesitant to have it come in contact with wine immediately afterwards and would instead follow One Step with an acidulated, then clean, water rinse. For the acidulated rinse, use 2 tablespoons of citric acid to 1 gallon (4 L) of water.
However, if you’re washing equipment before you store it long term, or if it’s something that you’ll sanitize again before use anyway, then certainly use One Step and don’t bother with the acid rinse.
As for using tap water with all your winemaking, you might want to see if your local water supply has chlorine in it. If so, you are putting your wines at risk of contracting TCA (trichloroanisole) contamination. Why not save money on all the bottled water and simply buy a chlorine filter?
Myself, I don’t like to use “secret formulas” to make wine; I like to know exactly what it is that I’m using in my wines and in my winery environment. I like to clean with Peroxycarb, do an acidulated water rinse then rinse with clean water. For sanitizing, I’m lucky enough to work in larger wineries so I use ozonated water to blast my microbes. Cleaning and sanitizing go hand in hand. If you can clean thoroughly with a combination of a basic cleaner (of which you know the ingredients) and good old elbow grease, there’s less of a chance that you’ll have a high population of microbes to kill later on. Don’t neglect sanitation but recognize its limitations. No amount of sanitizing can make up for the lack of good cleanliness.