Tag Archives: filters

Rainwater Catchment – Water Filter

With the container delivery in process, my thoughts have turned to catching water.  We’ve already done an analysis, and can clearly catch thousands of gallons of clean water off of the two container roofs, but I’ll need to add gutters to redirect the water, and I will still want to pre-filter the water before it goes into the tank to try to reduce the quantity of dirt that will get into the system (some will always manage to get in anyway, but I want to minimze that).

So I’ve been thinking about the filter systems I’ve seen floating around.  First, you want to try to avoid leaves and other “large” particles from even getting to a media type filter, so a pre-filter is in order.  One thought I had was to attach one of the leaf over-flow covers onto the top of a gutter section. These are the sorts of things that use surface tension to keep the water flowing into the gutter while the leaves are supposed to just shoot right off.  Since I won’t be in a position to place full length gutters the day the containers arrive (expecting early on the 17th), I was thinking of just placing a tarp along with a short section of gutter fastened to a cistern. This will at least allow us to capture some of the initial influx of rain, and let me test out the filters I’m considering.

The first actual filter is one I’ve seen described in a few rainwater catchment documents and sites,called a bypass filter. Basically, it’s a tube that hangs down below the downspout and has a slow leak valve at the bottom and a floating captive ball in the tube.  The idea is that the first “flush” from the roof/tarp dumps its dirt into the bypass (expected to be fairly fine stuff, light blow-sand, etc.), floating the ball up to the top where it eventually blocks off the bypass.  The rest of the water then flows across the bypass to the cistern.  The bypass will slowly leak out and will re-fill from a continued rain event, or eventually empty out and be ready for the next event.  Eventually it will become necessary to wash out the bypass in order to get rid of the accumulated muck.  My model includes a standard outdoor faucet for the slow leaking valve, which may even be large enough to allow a washout of the bypass without having to disassemble the filter all together.

The second filter is a sand and charcoal filter.  This is fairly straight forward, with the only “trick” being that I expect to line the outlet of the filter with a piece of geo-textile to act as a screen against sand and charcoal being flushed out and into the cistern propper.

So other than this model forcing the cistern deep under ground, I think this is the solution for rain catchment.