The standard (gold standard if you will) for our sodium hypochlorite strength that we mix with our GM6000 is 10%. That being said, it can be quite difficult to locate bleach, pool chlorinating liquid, etc. at that strength. Most available bleaches carry a 8.5% strength at best and often down in the 5% range. You can sometimes find it in the 12% neighborhood but typically at a prohibitive cost. After scouring the web for hours I've finally been able to locate the golden elix