I can't really comment on washing the straps long term in a washing machine. All I ever do is run a tap to the temp I wash my hands at, work up a lather with liquid antibacterial soap (the "Cien" brand from Lidl) and wash the already soaked strap between my hands. Then a good rinse and a pat with the towel and out on the washing line. As far as I can tell this works fine with no problems.