I'm starting a long delayed home construction in a rural area with no plumbing codes in force. I plan on laying out the under slab DWV lines. Below in my amatuerish plan which I'm sure has glaring red flag issues that I need to adjust. Can you offer some input ? The main waste line run is about 40 ft long which will amount to a 10" drop from start to finish. How much below the slab floor must I start the high end of the run ?


http://img.photobucket.com/albums/v123/squeeky/DWV_PLAN.jpg

You'll notice I made a few changes and brought your plans up to code.
Starting with the kitchen sink I Moved the vent back to within 5 feet of the trap and increased the drain size to 3". With garbage disposals being installed 2" just wasn't large enough. I removed the 90 degree turn in the washer drain and replaced it with a 45 degree drain to reduce friction and clogs.
I connected the drains from the utility sink and the lavatory directed to the vent which then became a drain line that tied into the sink drain with a 3 X 2" combination wye and eighth bend.
I deleted the 3" vent stacks as unnecessary. You're only required to have one 3" vent in your system and I'm assuming you already have one. The toilets will wet vent themselves with no help from us.
I also added cleanouts at the upstream end of each main,( You'll thank me for it later when you have a clog.)
Moving up the line to the tub and shower I saw you were draining the shower into the tub but were only venting the shower. You can't do that so I drained the tub directly into the main and tied the shower into the tubs drain with a 2" combo and moved the vent so it was a common vent for both fixtures.
You may see the changes by clicking on the attachment.
And your thoughts on this? Regards, Tom

Thank you for the help. Can you clarify a few points :
. You removed the 3" vents explaining that only one was required and you assumed I already had one. The (2) shown were the only 3" vents. Do I need to add one back ?
. The kitchen line show a straight lateral tie-in to the main with no drop.
Will this be OK ?
. Do the clean outs turn up 90 deg and stub out through the slab floor ?
. What is a 3 X 2" combination wye and eighth bend ?

Thanks,
squeeky222

". You removed the 3" vents explaining that only one was required and you assumed I already had one. The (2) shown were the only 3" vents. Do I need to add one back ?"

If you haven't a 3 or 4" vent stack in your system I suggest you make the kitchen vent 3" since you're already tied into the main 3"

"The kitchen line show a straight lateral tie-in to the main with no drop.
Will this be OK ?"
I don't understand the question. I did not draw a straight lateral tie-in.
No Drop. Do you mean the drain will have no slope?

"Do the clean outs turn up 90 deg and stub out through the slab floor?"

You can terminate them that way. A better way, if you have room, would be to eighth bend up to the floor instead of using a elbo.

"what is a 3 X 2" combination wye and eighth bend ?"

It's just what it says. A combination fitting, (see image) called a "Combo" is a wye with a attached eighth bend. This is used in place of a sanitary tee in drainage to reduce line friction. Regards, tom

I appreciate the explanations. I guess I miss-worded the question about the lateral drain tie-in to the main from the kitchen. The drawing shows the line extending from the vent in a diagonal fashion and then turning to the right and connecting to the main waste line at a 90 deg angle. It's the drop from the turn to the main that I'm referring to as lateral. The main will drops in the west to east direction and the kitchen line (after it turns) comes in from the south.

I appreciate the explanations. I guess I miss-worded the question about the lateral drain tie-in to the main from the kitchen. The drawing shows the line extending from the vent in a diagonal fashion and then turning to the right and connecting to the main waste line at a 90 deg angle. Its the drop from the turn to the main that I'm refering to as lateral. The main will drops in the west to east direction and the kitchen line (after it turns) comes in from the south.

The 3" kitchen drain line will extend over the 2" washer line and connects to the main with a turned down eighth bend that ties into a 4 X 3" combo turned up on a 45 degree angle. OK? Cheers, Tom