If you live in an area that experiences frequent droughts or you just don't like paying high water bills, there are a number of ways you can capture or reclaim the water that your household uses for other purposes.
First, I want to state that the suggestions I make in this post require very little in the way of equipment, installation or, really, intelligence. The main thing to know is that there are different kinds of water: white water (clean, potable water that you can drink), gray water (used water that may have some chemical or particulate matter in it) and black water (water that has fecal matter in it). Because of the high potential for disease, I'm not going to include black water (mainly water flushed from your toilet) in this discussion because processing that kind of water takes more than most people are interested in doing.
So, what kind of household water can you use?
Well, the most obvious is rainwater capture. Roof run-off collected in rain barrels is the easiest way of going about it, but unless you have multiple rain barrels stationed at every downspout, you won't get a tremendous volume, which is probably okay for most of you anyway. Additionally, most of us aren't interested in digging up the yard and burying a cistern, but that certainly is a great way to store your rainwater. So, I'm going to assume that most people will be willing to try a rain barrel or two, just to see what it's like before investing in anything more complicated.
What can you use your collected rainwater for? If you don't mind lugging around a lot of buckets, you can use it for flushing your toilets, washing your windows or any other number of creative uses in addition to watering your lawn and plants (indoor and outdoor). I also have a low-budget idea for using it for shower water (to be explained in a future post). I would suggest it for washing your car, but you should already know that washing your car at home is a bad idea unless you do so on a permeable surface to filter out the grease, dirt and other goop your car collects. We don't want that dirty water draining straight into the local waterways.
There are a number of potential issues that come up when discussing captured rainwater for use on food plants. Because of the dust, dirt, bird poop and chemicals that can leach from roof surfaces, you might want to look into a "first-flush" system where the first five minutes (or equivalent amount of rainwater) of runoff gets diverted away from your rain barrels. Kind of like rinsing off the roof before using the rain that falls afterwards. Of course, using captured water on fruit or nut trees shouldn't pose a problem.
Here I'm referring to the water that comes from your sinks, bathtub or shower that doesn't get used - mostly because you are waiting for the water to heat up. This water can be collected in buckets (shower/bath) or Tupperware (for smaller sinks and the kitchen). Water captured in clean containers specifically for this purpose can be used for drinking or filling the pet's water bowls. Remember, this water is clean and potable, it just wasn't the "right" temperature. Again, the water collected can be used for watering indoor and outdoor plants as well.
Water from the shower can be used for flushing the toilet (just dump it into the toilet bowl until it flushes) or really any number of the uses mentioned in the above section. Since this water is clean you can use it for food plants with no worries. One thing I like to do is to keep a rain barrel just for dumping warm up water since I know it has no contaminants in it (like the aforementioned bird poop and asphalt shingle juice) and can be safely used on food plants when the rain is less prevalent and I actually need to water my food plants (like during the summer versus the rest of the year).
Gray water gets a little more tricky, mostly because of what might be in the water. Used water from the bath, washing machine, and bathroom sink are considered gray water*. It's a little difficult to capture sink water (unless you divert it from the drain), so the easiest gray water to reuse is from a bathtub/shower and washing machine if your machine plumbing drains into a sink or is easy to divert.
Since we are dealing with water that potentially has some contaminants in it, it can safely be used on nonedible landscape plants only. Some plants may be sensitive to the sodium and chloride found in some detergents, but if you are using more natural cleansers this may not be an issue. Gray water may actually be better for your plants since some detergents contain nitrogen or phosphorus which are plant nutrients. Basically, the rule of thumb is to experiment in small quantities with plants and see how it is tolerated and/or use biodegradable soaps.
I would also caution against using diverted washing machine water if you are doing a load of cloth wipes, cloth diapers or the like that may contain fecal matter, since you don't want to be using this water without some extra precautions. In addition, don't keep your gray water sitting around for more than 24 hours, since there is an increased risk of growth, bacterial and otherwise.
Gray water can also be used for watering fruit trees, flushing the toilet or pre-rinsing those poopy cloth diapers. Finally, some areas have laws against using gray water. Since you aren't employing some huge gray water system in the yard, I can't imagine you'd run into any problems, but you should look into it, if you end up diverting all your washing machine water out into the yard or something of the like.
*Water from the kitchen sink drain, garbage disposal and dishwasher usually is considered black water because of high concentrations of organic waste.
What kind of household water do you capture or reuse? If you aren't doing any of the above, which would you be interested in doing?