Gutter to buried pipe to catchment?

[Hunt Stoddard]

Also, yes, if you're cleaning your roof or gutters, just unscrew the plug; do all your cleaning and let little stuff go down the downspouts. It will all be deposited outside the cleanout after the next big rain. Even with a tee, this stuff is unlikely to go into your tank, since the moment the water level reaches that of the cleanout, it will dump out of it. Of course, it's unadvisable to allow big stuff to go down your downspouts. Also, put a coat of teflon on the plug; otherwise, PVC plugs tend to bind to the PVC thread and no amount of torque can release them without cracking the pipe.