insulated concrete form house

[iffy]

Code says minimum 1/8" per foot, maximum 1/4" per foot for sanitary sewer.

[Raider Bill]

So 1 inch per 8 ft pipe is the answer.
Would a 4 inch pipe be better than a 3 inch?

[tim1234]

As said before 1/8" per foot is the minimum.  1/4" per foot is the maximum.  If you are too flat (less than 1/8" / ft) the liquids go to slow to move the solids.  If you go too steep (greater than 1/4" / ft) the liquids outrun the solids.  If you stay in the range above everything will move at the same speed.  If you need to drop suddenly, run it at a 45° angle to let all the "stuff" fall together.

So somewhere between 1" and 2" of fall for every 8' of pipe.

Tim

[Raider Bill]

What about a larger diameter pipe? Will that help, hinder or doesn't matter?
My idea is to have black water only go to the septic. Gray water will be routed to a sepreate system.

[Furby]

So 1 inch per 8 ft pipe is the answer.

Not really as I don't know anyplace that sells 8' pipe! ;D
It normally comes in 10' lengths, but 20' and even (rare) 40' are out there as well as 5' at the box stores that cost almost as much as the 10'. :

[tim1234]

Hey RaiderBill,

Thanks for making me feel useful.  I can finally post on something I know about.  Not a plumber, but did replace all the plumbing (including everything else) in my house and did a lot of research.

The best book I fould was "Plumbing a House" by Peter Hemp.  I used it as a field guide while building my house.  I can highly recommend it.  It is from Taunton.

Just curious, are you meaning black water to be solid waste and grey water to be liquid waste?  I would be careful seperating the 2 as you might not have enough liquid to lubricate and push the solids along.  You need an expert opinion on that one.

The answer for the size of your DWV (Drain Waste Vent) piping comes from how many fixture units will be flowing through the pipe.

For instance a:

Tub = 2 units
Bidet = 1
Shower = 2
Toilet = 3
Bar sink = 1
Kitchen Sink = 2
Lavatory (bathroom sink) = 1
Laundry sink = 2
Washing Machine (standpipe) = 2

The required size of pipe depends on if the pipe is horizontal or vertical.  Since you are talking about horizontal I'll address that.

Max fixture units for each size pipe:

2" = 8
2-1/2" = 14
3" = 35
4" = 216
(there are exceptions to these rules).

Add up all the fixture units and then you have to use the right size pipe.  Most DWV pipe in the ground is 4" min.  3" is used for some horizontal runs that meet a main 4" pipe under the slab or the main exit of the dwelling.  3" is also used for most vertical stacks since they fit into a regular stud wall (good for 48 fixture units vertical).  The horizontal length of any size pipe is unlimited assuming 1/4" per foot of fall.

Hope this helps.  If you have any more questions, let me know.

Tim

[Furby]

Seperating the grey and the black water really isn't that big of deal.
I don't think most folks run their shower while they flush the toliet, so there isn't much different with a standard hookup and the two seperated.
In fact, it's a requirement to seperate the two in places out West.
They then treat the grey water and send it back to be used as tank water in toliets.
Google: grey water

[Raider Bill]

I figure if I only put tolit water in the sptic I'd be further ahead and use the gray water for irrigation or intalkl a dry sink.
MAybe thinking too far into this as I live alone so don't make too much waste.
It will be a 3 bedroom house in case I decide to give to to my son someday.

[Fla._Deadheader]

  Typically, Sanitary goes into the septic. All others go into a different tank for gardens and such.

  Ever check on composting terlits ???  Them requires no water OR Plumbing ???