Thanks, Daox. That's an interesting link.
The problem with roof washers is that they only work as designed in areas that get downpours in between periods of no rain. As the fella experienced, being in drizzly Oregon, they just require a heck of a lot of maintenance to keep them functioning. Even in moderate climates like here in the Midwest, they just don't work so well. It's better to just collect and filter it all.
There's a company out there called WISY that makes a filter that is an integral part of the downspout that filters all the water coming through, so it wastes much less rainwater. It's basically an inverted cone shaped screen that the water would stick to and get diverted to the outer wall of the downspout, and the debris would fall out the bottom. Viola, less maintenance. But again, pricey stuff, which is a concern when you're trying to engineer a commercial solution. We DIY'ers can cobble one together for a fraction of the cost for our own residence, though.
