Clean water usually does not come for free. Water purification and transportation costs energy and most energy generation pollutes incl. nuclear power. Saving water is better for the environment in many ways. That's why low-flush toilets, low-flow shower heads, "grey" water circuits etc. are invented and encouraged.
I use the "Ilford method" and presume that Ilford tested that method before publishing it. I haven't done any testing myself.
And remember less than 1% of the water here on earth is fresh. Some 20% of that is in the Great Lakes. Read "The Ripple Affect." You will view water in an entirely different light.