Under-slab Plumbing

July 1, 2009
Today the plumbers started laying the sewer drains in the cottage. The drain runs are fairly short, and stubbed outside for a future connection to the septic tank once it’s installed.

Here’s a view of the drain lines from above. From top to bottom are the kitchen sink, bathroom sink, toilet, and shower.

We also started laying 2″ plastic conduit through which we’ll push the PEX tubing for hot and cold water supply after the slab is poured. This way is a lot easier to run the tubing under the foam insulation because the conduit stays put, and in the unlikely event that these lines ever freeze we can just pull out the old tubing and replace it. The cold water conduit shown here just runs through the sand, and the hot-water lines will run in a separate conduit with foam insulation all around it.

July 3, 2009
The plumbers finished up the under-slab drains for the main house. These lead out underneath the garage slab, and the main house drain will join the cottage drain outside before entering the septic tank.

July 5-9, 2009
After back-filling the sewer drains, the plumbers ran conduit for the cold and hot water supply lines in the main house. All the gray tubes are conduit, through which we will push 3/8″ PEX tubing to supply hot and cold water to the fixtures. The blue lines supply water to the outdoor hydrants.

We put 3″ foam insulation underneath the hot water runs. Later we’ll butt the first layer of under-slab insulation against the conduit, and then cover it with the second layer of under-slab insulation so the whole thing has at least 3″ of insulation on every side. This insulates the hot water pipes to R-15 or better below the slab.

July 9, 2009
This shows the water inlet to the cistern. We had the plumber use PVC pipe and fittings that are all rated for potable water so the pipe won’t introduce contaminants into the water. Even if we don’t use it as a potable water supply in the near term, this keeps our options open.