Sand to protect underground drain pipes? Also, two way cleanout question...

I know my local code (UPC) requires that pressurized pipes be protected by sand (or clean fill?) before backfilling with dirt...

But, does anyone know if there is a similar requirement for drain pipes? I'm getting ready to do underground drains for my bathroom addition and I'm wondering if I can just backfill over the pipes with the dirt I dug up (after inspection of course), or do I have to put down a layer of sand under and/or above the drain pipes?

Also, I am putting in a two way clean out for the same bathroom addition. The pipe from the bathroom will be 3 inches, but the pipe it connects to in the yard is 4 inch clay. Can I use a 3" two way clean out, or do I need a separate clean out (matching the diameter of the pipe it serves) for each direction since one is 4 inches and the other 3?

Thank you!

Just make both cleanouts 4", and run 4" pipe to the clay line. The one towards the house will seldom, IF EVER, be used so it being oversized is not a factor. Use the same dirt to backfill. Before inspection, you have to pack the dirt around, and under, the pipe about half way up, it is called "shading the pipe". If you are in Scottsdale, or a few other cities, they REQUIRE that the water lines be enclosed with insulation for protection and heat retention, but then you can use the same soil for backfilling.

I used sand in my basement because I needed to try to compact it under a fairly tight network of pipe.

If you get enough water in there to saturate the sand, and then keep adding water, it will help.

Thank you for the detailed and helpful information! I really appreciate it.

Just as a point of information, so far, I have NEVER "imported" sand or any other fill material for my water or waste lines.

hj said:

Just as a point of information, so far, I have NEVER "imported" sand or any other fill material for my water or waste lines.

Click to expand...

Hey hj, Do you think it would make a difference in areas with highly expansive soils (clay)?

(trying to learn, not disagreeing)

I guess if you do all of your work in the exact same area, you might never come across rocks, clay, etc. etc.