Solutions for roof run-off -- Dry well?
I am in the process of regrading and repaving my back yard closest to my house. We took up the old cement…
I am in the process of regrading and repaving my back yard closest to my house. We took up the old cement and are now down to dirt. The plan is to get the slope right and then layer gravel, sand and some kind of stone (bluestone, flagstone) on top. So, no layer of cement, and no grout between the stones.
The roof run-off comes straight down the middle of the house and then across the patio section. This had destroyed the cement there before, and it is an even worse idea for a sanded stone area.
One solution is to re-rout the roof water back into the house sewer line. But I’d rather avoid this expense if necessary.
I really cannot see any spot to drop the water in the yard. We have an extension, a shed, and a landing for deck stairs that all need to be protected.
Has anyone tried a dry well? What you do is dig a hole large enough to put a perforated trash can into, fill the can with large rocks, and then run an underground line to the can. The dry well can be covered so that you never really know it’s there. The water fills the well and then seeps into the ground through the holes in the can. Of course, if the can gets filled up in a big rain the water will need somewhere else to go (you leave a gap between the pipe to the well and the roof’s downspout to allow for spillover.) I suppose it’s also possible that the ground water will fill the well on its own (we’re very near the Gowanus). So, it’s not foolproof.
However, it still sounds neat. Anyone have any thoughts? If I use a 30 gallon can for the well, is there any way that it would fill up in a heavy rain? (My roof is 35 x 20.)
Thanks.
Of course it’s legal, every brownstone in my block was built that way.
Before you go and put the rain water into the sewer system, check out if that’s even legal. I don’t think it is.
I used a concrete drywell. Its 6′ high and 6′ in diameter. Never fills up. My roof is 55′ by 18′.
you should definately drain the roof water to the sewer line. I can’t see why that should be more expensive than building that dry well you’re talking about.
In addition to the problems mentioned above, putting that much water into the ground may eventually cause it to leak into your cellar.
I have a center drain that connects into the sewer/storm system, so most of the rain that hits my roof goes that route.
BUT my house is on a natural hill and water drains toward it. Whoever built the house 112 years ago accounted for it by digging a deep stone-line pit at the bottom of one of the rear window wells (the low point of the property.) The pit used to connect to terra cotta drainage pipes under the sub-basement floor, but they became plugged or crushed over the years. Water still collects in the pit, and I use a utility pump to pump it out every day. It holds about 20 gallons, and there’s always groundwater even during extended dry periods. Most mornings, it’s full — rain or shine. All of which is to say, I think you’ll need a bigger dry well.
I have seen dry wells used the size of VW BUGS used in Brooklyn.
If you have 1″ of rain, your roof will catch approx 450 gallons of water (google: 35*20/12 cubic feet to gallons). If the rain fell over 2 hours, the 30 gallon can would effectively need to drain completely every 8 minutes. In an extreme storm you might get more rain in less time…
There was an article in This Old House magazine recently about storing rain water from roofing in specially designed barrels to use for gardening. I thought it was interesting from a recyling perspective… maybe check the website?