11-08-2008, 01:47 PM
Hi Kimo wires,
I designed water and wastewater systems on the mainland and the spec's/details indicated a "firm bed", but don't let firm be confused with rock. Drain pipe will fare better than pressurized pipe against rock, but I've overseen a couple of repairs where a single rock ~3" in diameter wore a hole through a pressurized watermain. My spec's called out 6" of bedding below if in non-suitable soils (rock or just rocky) and then 12" above and then above that 3 inch minus to the surface. The trick was in compaction around pipes, but even under slabs we allways compacted. Those spec's are designed to ensure a long life for sewer or watermain systems, both pressurized and gravity flow. Calling the county is allways a good thing and as a minimum always use pipe wrap for slab penetrations.
Cheers,
Sean
I designed water and wastewater systems on the mainland and the spec's/details indicated a "firm bed", but don't let firm be confused with rock. Drain pipe will fare better than pressurized pipe against rock, but I've overseen a couple of repairs where a single rock ~3" in diameter wore a hole through a pressurized watermain. My spec's called out 6" of bedding below if in non-suitable soils (rock or just rocky) and then 12" above and then above that 3 inch minus to the surface. The trick was in compaction around pipes, but even under slabs we allways compacted. Those spec's are designed to ensure a long life for sewer or watermain systems, both pressurized and gravity flow. Calling the county is allways a good thing and as a minimum always use pipe wrap for slab penetrations.
Cheers,
Sean
See you in the surf