I plan on building an OSP SIP house on a slab in northern WI & would like to find out what are the benetits/ pitfalls of burying drain pipes, water lines, and electrical under the slab.

Thanks,
Henry

Welcome from another Wi resident.  It is standard building practice to bury all under slabs.  But try not to as much a possible, makes more work to get every thing compacted under the slab.  I know of very few houses that don't have drain pipes and water lines under the slab in their basement. By code they must be pressure tested before the floor is pored  Now if you are building on a slab with no basement and need to get power to a island in a kitchen, then a conduit would be buried and the wires pulled after.  All other walls the electrical can be pulled in the walls or trusses.   Yes things can happen but very slim chance and they can be fixed just more work.  Go for it, no worries

If the attic is conditioned is there any reason why water supply lines shouldn't be run in the attic as opposed to under the slab? Seems like less chance of failure that way.

What would you consider conditioned in northern Wi. and how would you do this? Under the slab in a SIP home it would never freeze. I have never seen a house in this state that does not have the water line under the slab!

Right, I can see why that would be beneficial in Wisconsin. I'm in a wildly different climate here in Louisiana.

But what about those PEX manifold home-run supply systems? How is that handled? I assume the water service from the mains comes in under the slab and then the rest is run like electrical?

Jelly, In a home with a basement both PEX and copper are both run in the floor joists. On an interior wall, they are run up into the wall cavity. Then out in to the back of the cabinet/toilet. On an exterior wall they come up trough the floor. For any basement water supply they would run down in the wall cavity.

Carlo, I see, we're talking about the same thing. I was confused by "slab" in the original post.

Cheers!