Hard to get the title of this post to describe what I am thinking about. I am going to be building a garage later this fall and I’d like to install some sort of rainwater collection system that will feed a small mop sink/lavatory and maybe a urinal for the building. It will be more of a woodworking shop than a garage so I plan on spending a lot of time there. I really would like the convenience of washing hands, getting water for paintbrushes etc. I can plumb a drain directly to my septic tank which is about 25 feet away, but the water is more of a problem. I can certainly tee off my well but it will get such occasional use that I would prefer to find a way to recycle what comes off the roof.
I was thinking of either putting in a small plastic cistern/septic tank and gutter system to catch the water, and run from that with a small submersible pump to a pressure tank, inline filter and plumb to the sink. OR, putting a tank of some sort in the attic/rafter space and letting gravity feed the sink. With the pump system I think I can do hot water as well. My biggest worry is probably keeping the collected water clean and free of bugs and critters, although the filter will probably help.
What do you think? I know a lot of people in dry places are highly dependent on rainwater collection – how do they do it? I design water distribution systems as part of my job but I always deal in wells or municipal sources – rarely a shallow well or spring house. Rainwater collection is new to me. Also would need to figure out an overflow system too, I guess.
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Well, "scale" winds up being a huge part of rainwater sequestering.
"Small" tends to be the 3-40 gallon downspout barrels. These are just find for potted plants, filling garden jugs and the like.
"Medium" sized can be harder, getting to the 1-1200 gallon range. This is hardest, as it's almost the least-used size. But, you are nearer to useful quantites of water for actual plumbing fixture use. that's only 4-5 500 gallon bladders, which will go under a fair-sized porch middling neatly.
"Large" gets to be just that, dedicated tanks and storage over 6000 gallons (know of one near Austin that has 12000 gallons of storage available--but, it is dedicated to irrigation, too).
One of the big issues is how much surface area of the water is exposed to air. More exposure is less-good. You need traps to make air gaps, and debris screens and the like. Otherwise your rainwater will go "grey" on you, and not in a good way.
Which also means you need rainfall tables, and records and averages to design the system, too. Austin is wierd that way. About 24-18" annually; but with 6-12" per 24hr day rainfalls likely. Whereas, over here in Bryan, we get (usually, not this year) about 36" per year, and average right around 3" a month, with a 24 hour design load of about 4" in a 24hr day. (Record, though, was Alicia, we had 17.45" in 24 hours.)
It's do-able, just takes some work on the design end. With the next hardest bit being getting the tankage.