in my past travels i have come across a item of kit called a millbank bag its used to fillter water before adding tablets or boiling. its made of tightly woven canvas fabric and looks like a big sock. sure its low tech and slow but it works well ,does not clog or break. the bag works this way simply fill to marked line on bag squeeze to soak and then let drip into cup or water bottle add your tabs and your good. to clean shake out dirt let dry and you can use it again and again.our brit and aussie friends know what this is as it is a brit item..