The purpose of this Instructable is to show how to catch and store roof runoff for various uses.Most, but not all states allow this. You should check your area to make sure it's legal.
Step 1: Installing Gutters
The gutters are installed with clips that hold the aluminum bodies where the rain will run off into the roof into them. You need to have at least a half inch of slope towards the downspout. While you are installing them, it is best to put some kind of guard to keep your gutters from being filled with leaves and other debris.
Step 2: Moving the Runoff
After the water leaves the gutters, it should be diverted into a pipe for transport to the first flush diverter. The better this step is sealed, the less you have to worry about contamination in your runoff.
Step 3: The First Flush Diverter
The pipes come from the gutters from both sides of the building. They meet in a T and go down past the leg to the tank and into larger pipes set up to hold the first five or six gallons of runoff. This is to improve the quality of the water reaching the holding tank. The water that gets diverted here should contain most of the dirt, bird droppings, dust, and pollen. The bottom of the pipes is threaded on loosely and there are holes bored in the caps to allow water to slowly trickle out so they will self-empty.
Step 4: After Diverter to Storage Tank
After the first flush diverter fills up, the water pressure will then push the rainwater through the side leg to the holding tank. I used an intermediate bulk container (IBC) that holds about 250 gallons. It was food grade product and I washed it out several times to get the best quality water. The IBC is wrapped in several layers of black plastic to keep down the light so no algae will grow. As the downspout enters the IBC, I put a Y on the pipe and covered that with a mesh paint strainer bag. That way, when the water displaces the air in the IBC it has an exit and when the IBC is full, it acts as an overflow. The bag prevents vermin or insects from contaminating my water
Step 5: From Storage to Use
Mine goes from the IBC through a valve under my cabin into a hand pump inside. It could also go to a hose for watering or even an irrigation system. I don't use this water for consumption without filtering it.