Sewer lines for new house
 

I am building a new home on a slab. I have done quite a bit of piecemeal
plumbing in the past, but this is my first complete DIY system. Hope some
of you seasoned plumbers will help me out. I think I have the layout figured
out but have a couple of questions about how to proceed.

I will have dual parallel 4" pvc drain lines running the length of my 60-ft. long
house. One will have the five commodes draining into it and will go directly
into the septic tank. The other will have all other fixtures draining into it and
will have a valve so I can divert it onto my garden, or into the septic tank.

Should I lay the full length of the two 4" drains first, and then come back
and tie in all the wyes from the fixtures? What do I use to secure the
pvc in place until the slab is poured?

I am using PEX supply lines. Can I use standard foam pipe insulation for sleeves to protect where they come up through the slab? I was thinking
of using re-bar stakes to secure them in place until the slab is poured. Is
there a better option?

Would appreciate any pointers anyone could give. I am an experienced DIYer
and very much enjoy accomplishing these things myself, in addition to the
money I save. So far, my son and I have surveyed and laid out the foundation. He dug it with a backhoe, and I cleaned out the trenches with a shovel by hand. Then I laid all the re-bar myself and set the grade stakes,
and we poured the footing. I am hiring the blocks laid (the time factor)
and then will be ready to start the plumbing. Thanks for any help!