# Depth of drain pipe under slab



## Mudball (Jun 9, 2006)

I have one ditch dug and one more to go for the 4" drain pipes under the slab. I have more trim digging to do depending on what the distance should be between the top of the horizontal 4" drain and the bottom of the slab. My plan is to dig the ditch deep enough to put a thin layer of sand in the ditch for the pipe to lay on and then cover the pipe in more sand and small river rock (pee gravel)...Im shooting for a 3" space between the top of the drain pipe and where the bottom of the slab will sit. Does this sound like enough space ?
Thanks


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## glennjanie (Jun 9, 2006)

That's perfect, mudball! I think you will come out OK on this job. May I revisit the fall issue? You said the sewer will be 60 feet long, National and Kentucky Plumbing code say 1/4 inch per foot is acceptable. If it falls 1/4" per foot you have 60 quater inch drops. 60/4=15 inches or some of us need to sit down with a tape measure and count the 1/4" increments in 15"; just to see if you come up with 60. I rest my case.
Glenn


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## Mudball (Jun 10, 2006)

Thanks glennjanie. It looks like we are going to be sitting perfect on the correct amount fall for the pipe.
When you said..."That's perfect, mudball! I think you will come out OK on this job." Did you mean that Im ok on the first question as far as on the amount of distance between the top of the pipe and the bottom of the slab ?
Im actually referring to the highest (most shallow) the beginning part of the pipe because after that, the pipe will be dropping deep enough under the slab with plenty of gravel over it to protect it from the slab. Im concerned about the highest part of the pipe. Does that make sense 
Sorry if I dont make questions very clear. I would say its because of my lack of experience and/or terminoligy...but Im learning. So 3" is ok ? 
Thanks


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## glennjanie (Jun 10, 2006)

Good Morning Mudball:
Yes, the begining point being 3" below the bottom of the concrete is perfect. You can carry a 1/8" per foot fall from there to the foundation line. Then, when you get outside the foundation you need to install a test tee so you can seperate the building drain for testing. Kentucky code requires 18" cover over the sewer outside the foundation line which can be achieved with a 45 degree drop. Then the 1/4" per foot fall would be carried from there to the septic tank or other point of disposal. If your ground falls faster than that, you can make more 45 degree drops to keep the sewer 18" below the ground.
Glenn


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## Mudball (Jun 10, 2006)

Thanks glennjanie. That sounds great. I'm so tired right now 
Is has been a very hard hot long day. I guess I'll get it done soon. Thanks for the help. It looks like everything is going to be alright...in time


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