# Need a math geek or hydro engineer



## FLWhaler (Oct 1, 2007)

How much water per hour can a 3'X3" pit with 4"s of pea gravel on the bottom disperse? Putting in a miniature septic tank for grey water. Don't ask why.


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## stripernut (Jun 15, 2013)

FLWhaler said:


> How much water per hour can a 3'X3" pit with 4"s of pea gravel on the bottom disperse? Putting in a miniature septic tank for grey water. Don't ask why.


It will depend on your soil texture, i.e., sandy soil quite fast vs slow for the clay. If you really want to know for your specific site you can do a simple perk test: bore a hole to the depth you are making your pit and fill it with water. Keep filling it for an hour and then measure with a tape how fast the water recedes. The result is inches/hr. If you need more info google perk test and you should get lots of results.


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## Mike W (Jul 11, 2011)

Coming from a civil engineer with a minor in water resources engineering...there's too many variables to just "jerry rig" it as everyone likes to say. As stated above, the soil types below and a certain radius around the pit are very important, the depths of those different soil types below and around the pit, the compaction of those soils, and many other things. Plus, the rate the pit can disperse your grey water will vary depending on the time of year, depth of water table, recent rainfall, and a few other things. 

Don't take this the wrong way (I honestly mean no offense), but I'm guessing by your "don't ask why" comment that you're just trying to put in a small tank somewhere without getting permits and inspections. While as an engineer I can not and will not ever endorse that, I will say the following from seeing people try to do this and fail: find someone to do the proper tests in the area you want to install it on the basis that "maybe I'll install something later". Then say you changed your mind and aren't installing anything, use the data you received, and do it "under the radar". I'd just hate to see you spend money on installing it and have to possibly re-do something in a year or two. The data from soil tests can go a long way.

Best of luck and tight lines.


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## FLWhaler (Oct 1, 2007)

Really good info here. What I'm doing is simply putting an outdoor sink to rinse off my hands when doing yard work etc. Trying to put something in so it doesn't just run out on the drive. It won't be used very often or very much so I figured a miniature septic tank might be a good solution. So a 3 X 3 pit with a 28 X 22 inch fiber glass tank with 4 inches of pea gravel below and around it was my first idea. Just trying to figure the disperse rate. Any ideas are appreciated and I won't take any offense to opinions as well.


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## Mike W (Jul 11, 2011)

Your idea in theory would work well if the soil types underneath will allow that kind of infiltration. Were you thinking any small field lines, or simply the tank in the ground and all infiltration occurring right underneath it into the pea gravel?


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## slayerextreme (Jan 10, 2012)




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## jaster (Oct 7, 2007)

I did one for my washer. Two 55 gal drums, 4" pvc pipe connecting them, two drainlines with a r9ckbed under em. Never had an issue!!!! Better to go a little bigger now than relize you should have gone bigger to begin with? I suggest atleast one drain line?


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## Orion45 (Jun 26, 2008)

FLWhaler said:


> Really good info here. What I'm doing is simply putting an outdoor sink to rinse off my hands when doing yard work etc. Trying to put something in so it doesn't just run out on the drive. It won't be used very often or very much so I figured a miniature septic tank might be a good solution. So a 3 X 3 pit with a 28 X 22 inch fiber glass tank with 4 inches of pea gravel below and around it was my first idea. Just trying to figure the disperse rate. Any ideas are appreciated and I won't take any offense to opinions as well.


Outdoor sink to rinse off your hands after yard work? If that's indeed the case, just rinse your hands off under any of your outdoor bibs and the water will be absorbed by the soil without any problems. You could also install a sink in your garage.


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## WhackUmStackUm (Jan 31, 2010)

42


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## chad403 (Apr 20, 2008)

Wash machine tub. Make a French drain


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