napisan is really old fashioned and shouldn't be used on modern all in ones, that have a pul outer as it damages them, i also find it makes any bamboo insterts that you use really crunchy. i use the tots bots potion or the mio one which you can get in boots etc. that and a tablespoon (at the most) of ordinary washing powder.
they both sanitise at 30 so i wash mine at 30 and haven't had any stains etc and have used mine for 6 months so far...