I know everyone(many/most) is not fortunate enough to live in an area with excellent well water/spring water, but in my area of the country we are blessed with terrific natural water that comes up out of the ground. I am sure that many millions of others are also fortunate in that way. It makes terrific beer ,wine and whiskey without modification/alterations, and I have used it to wash buds a couple of years (since first reading of this). I assure you, that good water, that makes good beer without additions of gypsum, salts, etc. will be quite suitable for washing plants! Waters that taste good, will allow the baking soda, lemon and H2O2 to properly interact making a good surfactant effect and leave ,if anything, a healthier product than distilled water, even with (or because of!)beneficial traces of minerals that will be present! If your water is coming from miles of municipal pipes and is treated with chorine, fluoride and the like or comes out of the ground smelling of anything, leaves crusty mineral deposits around taps, or is hard and does not rinse off soap well, by all means use distilled water! I am a little lazy and confess that since I never use any foliar applied products (only compost, kelp and fish emulsion applied to the soils only) I now usually only do a quick rinse in plain old water without anything added, one warm and one cold, just to remove any dust or possible bug eggs/larvae (indoor grows only nowadays for me) Please, do not spray anything on your plants you would not eat directly! Plants can and do absorb and/or translocate some things through the foliage and some will not wash entirely from the plant without vigorous scrubbing! I guard against disease and insect problems and on the very rare times mites have shown up, I trashed the plants, cleaned up and started over! Washing plants with a garden hose with a firm but fine spray outside will probably work just fine to remove dust, a day or two before harvest ( also can temporarily help with mites). If you know of anyone using any chemical pesticides on cannabis intended for human consumption, kick their butts and/or spread the word against them in the customer circles. Poisoning people is bad, even when done unwittingly! I heard of a man who was using systemic pesticide purchased from the garden center, applied sprinkled on the soil, intended mostly for roses, cotton or other ornamentals, on pecan trees and he seriously injured some people who ate them(the pecans) months later! However, It does not have to be systemic pesticides to be dangerous ! I want only bud when I smoke, no oils, excessive dust, soaps, chemicals, or topical fertilizer residues and hopefully little bacteria and fungi! So, do the wash thing! Lay off of the pesticides completely! (There will be some dust, mold and bacteria always, since all the atmosphere has some dust, mold or bacteria floating about)
Icy cold water will make the trichs brittle, and they'll fall off. Be careful with the low temp rinse. 13 is just fine. 
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