With an acre in beds, my water bill can be as much as $600 per mo. in summer. As of now, we've had 11 straight days over 100 degrees and expect at least 7 more above 104 so will be on water restriction soon. I use a 3 gallon bucket in the shower- about what I collect in my three minute showers, and a small plastic container under the faucet when brushing teeth. When washing hands or cleaning fruit and vegetables, we collect the water in a small plastic dishpan. In three years, we've seen no harm to the potted plants on which this is used. We've had a homemade rain barrel system for five years now. Blue or white 50 gal. barrels are great (don't use if they've contained anything dangerous) Wash thoroughly. You will need short sections of flexible pipe about 2" dia. to connect the barrels near the top. Use a drill with the attachment that cuts holes for doorknobs to cut the hole choosing the pipe size accordingly. Use plastic flanges (plumbing dept. of HD) on the inside and outside of each barrel to seal around the pipe. Hook as many together as you'll need, with the first being under the downspout. Drill an overflow hole in the last barrel. Put a faucet at the bottom of one or use a sump pump to empty on beds. Clamp screening on top with the ring that is on the lid of the barrel. Spray paint to match your house if you like--you can even bury them partially. We are in the process of chaining at least 10 together in anticipation of Sept. rains. Yep! It's tough gardening in Texas.
We live in coastal Oregon but water often is scarce during the summer months into October. I have a large whirlpool tub in my bath. I use it often with just hot water (no soap etc). What a waste when 80 gal goes down the drain. Since the tub has a circulating pump on it I don't see why I couldn't pump it into a collection system. My very unhandy, nongardening husband thinks I'm nuts. (I know, you are thinking why do I keep him around, ha!) Have any of you ever done anything similar. Tub is on an outside wall and the pump is accessible from the laundry room also on an outside wall.