I use Bubba Moo an Aussie brand (I have a few others but that is by far my favourite as they are 1 size fits all and have lasted from 3 months to 25 months so far, with great absorbency and minimal leaks) and they recommend washing without any detergent, then every month or so (or more frequently if smelly) do a strip wash using a few drops of dishwashing detergent. We also wash in cold water and only do the strip wash in hot. This is economical, environmentally friendly and the nappies are fine. I dry on a drying rack in the sun where possible (on balcony if dry or not too humid, in front of the window if not) as the UV makes a huge difference to both stains and smell and using the dryer is not good for absorbency or life of the nappies, especially the covers. I was concerned how i would go in HK as they were line dried outside in Australia in a very dry environment, but it has been fine. I dry pail them in between and wash every two days. I also use flushable and biodegradable nappy liners most of the time as this helps with minimises poo stains and having to scrape it off which is often not that easy!!!