Installed prior to my ARCSA training at my home.
Prior to knowing about ARCSA and the training classes they teach, I installed this 1,000 gallon tank with a rainwater basket under the top cover. I used 2.5 inch pipe and ran it from the gutter to the underground drain below. In between, I cut in a ball valve so I could manually leave it open during the first rain to flush off the bad stuff and then close it to divert clean water into the tank. I ran the overflow back down and under the ball valve. This was before I knew about downspout filters and first flush devices. Bottom line the system works well and the water is clean. It easily passes through my compression pump and I use the water to augment my regular irrigation schedule. The tank was originally black and we painted it to blend in with the home color. A good example of DIY with a few trips to the local irrigation store.