When it comes to buying replacement filters, are there reliable sources for cheaper than OEM? Both in terms of reliable websites, and places to check up the reliability/certification of companies making replacement filters.
I have a 3M Aqua-pure filter, the price for replacement filters goes up and down, but right now it's ~$135, while other brands are selling for less than half that.
OTOH, I don't want to risk too much when it comes to drinking water...