The fifteenth capacity that I introduce in my eBook is that you must [be able to] collect and store greywater for later use. In it I state that:
You must “collect and store greywater for later use. Greywater is any water not fit for direct consumption, including water from laundering, dishwashing, and bathing. I might also include any water stored in something not obviously clean (such as a bathtub). Did you know you can reuse water in most instances (excluding bathroom activities)? So, can you store greywater? Should you? What will you use greywater for if you did store it? Maybe flushing toilets for starters. I’ve provided a greywater reference here.”
Wikipedia defines greywater as “…wastewater generated from domestic activities such as laundry, dishwashing, and bathing, which can be recycled on-site for uses such as landscape irrigation and constructed wetlands. Greywater differs from water from the toilets which is designated sewage or blackwater to indicate it contains human waste.”
Normally, all water from activities such as bathing, dishwashing, and so on go right down the drain without a though or care. You may quickly find need for such water in a grid-down situation. So long as the greywater is not being consumed directly (or used for cooking) then greywater may be suitable for any number of other uses. In a grid-down situation you may find yourself needing to capture this water for re-purposing in order to flush toilets (a very common use), water your garden, scrub the floor, wet a bandana, to make a cleaning solution, or whatever the need may be.
Because water is such a precious and often scarce resource (when you need it the most) it only makes sense to reuse as much as you can. In some cases you may be able to reuse greywater just as it is; in other cases it may need a bit of pre-filtering through cheesecloth or an old cotton t-shirt in order to be reused (such as with leftover water from cooking pasta, for example).
You can store greywater in any number of locations. The bathtub is a possibility but not the best idea; you would need to better seal the drain if you’re going to do this. Other ideas are 5-gallon home buckets, trash barrels (32 gallon and larger), plastic storage bins, any other bins lined with trash bags, kiddie pools, etc. Basically, anything that is not considered food-grade but will hold water is a storage option.
Just remember that any greywater collected should never be consume, even if filtered or boiled. This advice also applies to bathing activities as well.