We've begun collecting rainwater!
This is a HDPE barrel set atop a shipping pallet that I took apart and rebuilt into a frame. George and I worked on these together! In typical George fashion, he started on the project and insisted that I help NOW even though I was already time committed in two other places and activities, but I kept my cool and negotiated a solution that worked out.
George collected a set of 55 gallon plastic barrels from Pyramid Brewery. These barrels held liquid apricot flavoring (and they still smelled really yummy). I went out and bought new spigots (or hose bibs, for those of you who love correct terminology) which threaded right in to some nice holes in the barrel's caps. Together, we re-worked the downspouts to shunt water away from the foundation and into the barrels.
55 gallons of water isn't really much, but the barrels and the pallets were free, several yards of ribbed drain hose was $20 from Urban Ore, and the spigots were just $4 each. This system is intended for two things: to start us in the practice of catching rain, and to keep the ground floor of the house dry. It does those things. Unintended benefits include successfully working on a project with George.
Some specific design elements:
There's a wire mesh screen at the top of the barrel to filter out leaves and such. I put it there so I can reach it to clean it out without climbing a ladder.
We used the barrel on its side because that gave us access to the female threads for the spigot.
The barrel is up off the ground so we get a little bit of pressure head on the stored water (rain comes out of the sky, so it costs no energy at all to store it up high. In the future, I'd like to have a catchment system that was 10 feet off the ground).
My plan for what to do when the barrel fills up is to place the end of the hose so it acts as the overflow regulator. I can tie the hose to a stake and hold the end up so it matches the water level in the barrel, and direct extra rain to anywhere within the reach of the hose.