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How to drain gray water from cabin to a dry well downhill about 50'.  RSS feed

 
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Location: Northern woods of Minnesota
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I'm building a small all season recreational weekend type cabin for fishing, hunting, and snowmobiling, etc, in northern Minnesota on Sandy loam. The plan for water is to use jugs elevated above a sink. I want to upgrade from the 5 gal bucket under the sink and go with a drain pipe to the outside. I plan to run a pipe down about 30' to 50' to a dry well down slope.  I'm wondering if I run the drain pipe from sink, no p-trap, straight through the floor with a 90° elbow to a pipe, buried in the ground then running down slope.  Or, should I stay away from 90° elbow and go with a less sharp angle and use maybe a 45° elbow instead.  Or, even go with flex pipe and no sharp angle at all?  Of course, I need to be mindful with freezing temps that can go well below zero Fahrenheit at times but with the pipe buried and covered with mulch, etc, I don't expect freezing pipes to be problem as long as the slope is enough to keep water flushing down.
 
Posts: 495
Location: Northern Germany (Zone 8a)
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hey daniel,
welcome to the forums.

i don t feel comfortable to run grey water into a dry well. it might contaminate ground water.
i don t think that you will have huge amounts of grey water. what about building a treatment thing nearer to the hut? simple thing would be to dig a hole and fill it with spongy things. mulch, composting material. grey water will soak into it and be treated by bacteria like on a compost heap. you might think about waterproofing the bottom of that pit and planting swamp-plants into or around it. maybe willows.
if you use biodegradable soap, that would work fine.

in our small hut, i pour the grey water unto the compost heap or under bushes.
 
pollinator
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The outside temp, a 90 degree elbow, or deep burial are all a moot point in your plan as long as your pipe can maintain 1/4 inch slope per foot. That way water moves out of your sink and to the dry well. You CANNOT use a p trap, or any trap, because it holds water to prevent the smell from a typical septic system from coming back into the cabin. Since you do not have this, nor heat 24/7/365 to keep the water from freezing, your trap would always break. But you won't have smells coming up from a dry well either. No water in the pipe, no freeze up.
 
pollinator
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Location: Central Texas USA Latitude 30 Zone 8
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I agree with Tobias that it would be best to run the gray water to a mulch pit. Preferably next to a tree.

http://oasisdesign.net/greywater/
 
Posts: 19
Location: Starksboro, Vermont
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About Travis's comment on p-trap...  I agree. In my place i just installed a waterless trap in the sink drain. It's got a membrane type closure that is suppose to work with freezing temps.  I put it in incase we ever close down our place for chunks of time in the winter, one less thing to freeze protect.  found it here:  http://www.hepvo.com/

good luck

 
Posts: 88
Location: Los Angeles for now, Maybe Idaho soon...
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Daniel Reed wrote:I'm building a small all season recreational weekend type cabin for fishing, hunting, and snowmobiling, etc, in northern Minnesota on Sandy loam. The plan for water is to use jugs elevated above a sink. I want to upgrade from the 5 gal bucket under the sink and go with a drain pipe to the outside. I plan to run a pipe down about 30' to 50' to a dry well down slope.  I'm wondering if I run the drain pipe from sink, no p-trap, straight through the floor with a 90° elbow to a pipe, buried in the ground then running down slope.  Or, should I stay away from 90° elbow and go with a less sharp angle and use maybe a 45° elbow instead.  Or, even go with flex pipe and no sharp angle at all?  Of course, I need to be mindful with freezing temps that can go well below zero Fahrenheit at times but with the pipe buried and covered with mulch, etc, I don't expect freezing pipes to be problem as long as the slope is enough to keep water flushing down.


DO NOT use an old "dry well" for basically sewage or grey water.  There is a VERY HIGH likelihood of contaminating the water table doing that.  This is EXACTLY the type of thing that gives homesteaders and "permies" a bad name, not to mention could possibly cost you a fortune in fines. 

Dig a pit at least 150' from any known water source... dry well, lake, river, creek, etc.  Dump your grey water in there.

As for the drainage:  If you're concerned about freezing, use a p-trap you can drain in the wintertime.  A p-trap serves a purpose... it prevents gases from the grey water or septic system from getting back into the house.  In the winter, if you drain the p-trap, I'd plug the drain after to keep out gases and fumes.  but I would never eliminate the p-trap itself. 
 
Tobias Ber
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Location: Northern Germany (Zone 8a)
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many people think it s best do put liquid waste deep into ground.
i ve seen an urinal build for males from a well-pipe put (a few meters) into the earth and topped with a sink-tub. water table there is about 2-4meter deep. so basically guys pee directly into the watertable. this is in an allotment colony, where other peoples wells might be only 10 meters away from that urinal... yuck.

i assume that most bacterial bio-treatment of greywater happens where it s warm and somewhat airy. like on a compost heap. not deep into the earth. so spongy things would work best. or to disperse it unto a big surface of soil. for example with these kinds of irrigation hoses that have holes in them.
if you can use plants to help, that s even better. like putting the hoses under trees or building a mini-swamp.

probably using a small field of stinging nettles could help. they re VERY hardy and nutrient-hungry.

just some thoughts ...

but keep it simple. this might be easier than digging a pipe into the earth.
 
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I use 4" black flex pipe, 2x 15' sections if memory is correct. THe version with holes for drainage. Suggest avoiding the dry well. Slight down hill pitch about 6' Has been trouble free. About 18" deep in zone 7, with no trap used in winter.
 
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