Wellwater question: Our wellwater was tested(we're selling our home) and the arsenic level came back high(.027) Our well is 600 ft. deep and has tested perfectly fine in the past.My question is: I used a cleaner to clean the sinks, faucets, and even inside the faucets( zud cleaner) before they took the water sample. Could any cleaner residue have caused this positive? I've read that arsenic and phosphates mimic each other chemically and wonder if there are phosphates in these cleaners