Replies

1. 
   Ralph_Wicklund | Sep 19, 2000 09:02am | #1

   *
   Johnnie,

   I know you'd like to have some solid numbers but I think the first thing you should do is find out what minimum slab elevation is required by code in your area, such as X inches above road crown or some other required benchmark. Then look at a prudent elevation, such as how high does the water rise during a good rainstorm in that area and what is the drainage.

   Then figure the run of your waste and apply the slope you want/need.

1. 
   Sami_Kader | Oct 19, 2000 01:29am | #2

   *I just finished plumbing my new slab-on-grade house. I am not a plumber, just a semi-knowledgable DIYer so take what I have to say with a grain of salt. I started from my furthest fixture (a water closet) and set my closet bend so that the joint was under the gravel, well beneath the slab (I tried to do everything so that there are only vertical drain pipes in the concrete - seemed like it would cause less trouble with potential cracking and damage to the drain lines). Sloped down 1/4 per foot from there and attached remaining fixture drains/vents as necessary. This gives you the shallowest plumbing trenches to dig under the footings. Backfill with sand, then base rock. You should check to see where you are going to end up as your building drain leaves the house and heads for the septic tank or sewer hook-up. This line shouldnt slope more than 1/2" per foot or solids will stay while the liquids go. you may need to adjust your drain lines accordingly if all of your plumbing is pretty close to the septic tank. Make sure to roll the santee vent connection for the w.c.s and showers at a 45 and use street 45s to get horizontal so that the vent line does not stick up into the concrete. Wrap all of the ABS in thin foam before placing the concrete. I ran all of my soft copper water lines in the same trenches as the drain lines to keep them well below the slab and away from leaching lime which can cause pinhole leaks later. I also ran the poly-sleeve wrap all the way along the copper rather than just where it penetrates the slab. Overkill? probably. most builders around here run the copper in the gravel beneath the slab bare so they have the shortest possible runs. I tend to be an overkill kind of guy with stuff under concrete (I hate jackhammer repairs). Good luck!Sami

2. 
   Johnnie_Browne | Oct 19, 2000 01:29am | #3

   *
   On a rough in on a new house slab, how deep under the slab does the main drain need to be. I know it need to slope appromate 1/4 to 1/2 inch per foot and I know the distance from the tank to the farther fixture. I just need to figure slab elevations.