In theory, yes. Of course, the same holds true for a lot of things which we currently use clean water for! The water needs of agriculture, toilets, carwashes, and many more could be addressed through so-called graywater (e.g.: pumped lakewater, rooftop rainwater) if we really sat down and wanted to make it happen.

The reason that we don't do these things is rather mundane: it's cheaper and easier to tap into the shared drinking water infrastructure than it is to collect your own water and roll your own silos/filtration tech. That might change as the world changes -- something has to give eventually if we use more groundwater than we replenish, but much like clean drinking water, I don't think it's a problem we should ask individual entities to solve. Governments would generally be much more suited to efficiently collecting drainwater, scrubbing it, distributing it, and mandating usage in wasteful commercial applications.