Tank No. 1 is for the primary effluent (polite speak for crap), and its divided into two compartments. About 60% is for the turds, piss, dish water, shower, etc., and the other 40% is for the gray water that comes off the brown water. Then the gray water gets filtered, and flows via a 4" PVC pipe into Tank No. 2, which you might call not-so-gray water. This tank is the secondary pump tank, which contains a pump, a float and inducer (signal maker for effluent level), and miscellaneous parts. Since we have a pressure (not gravity feed) system, the pump gets turned on a regular basis; depending on flushes, it may pump 50-100 gallons into the drain field every four hours (all this is to be decided by the septic engineer and our usage patterns). The design calls for 250 gals of inside water use per person per day, so our 500 gallons would be passed along to the drain field each day.
Watching the tanks get delivered and dropped in place was pretty special. Rocky (and sidekick Roxy, a brown lab with bad hips) backed the rig up to the holes, lifted the secondary tank and slide it in place like a pillow into its case. The truck has a 14 ft extension boom, which wasn't enough to put the primary tank in place, so Richard back filled around the secondary tank and Rocky backed up to the edge of it, just enough to drop the primary (upstream) tank into place. A little jockeying and all was well. Later this week, Richard plumbed the two tanks, laid the 4" sewer pipe to the house where I'll connect the ABS drain pipe (3"), and installed the pump. Richard will be back in about 10 days to do the manifold installation, lay the pipe in the drain field, and pressure test the system. At that point we’ll be ready for our septic system inspection, which is conducted by the County Health Dept, not the Building Dept.One complication in our layout is that the sewer and water pipes cross over each other, so we had to amend our approved septic plan (+$175) and install 2" shielded conduit for the water pipe. The logic, however flawed, is that during a big earthquake (the Cascadia one I presume) the ground might shake and settle, thereby breaking the sewer and water pipes, allowing the contents to commingle (always a bad thing) and polluting our water supply. That would be the least of our problems, since we wouldn't have water pressure (broken pipes, remember) to fight the ensuing fire that consumes the house. But I digress.
If all goes well, we’ll have the lot regraded to final form after the inspection in about 2 weeks. Richard will put 12-18” of material (mostly silty sand and gravel) over the drain field lines and then about 6” of topsoil. We can only grow shallow-rooted plants over the drain field, something like grass. Nancy prefers lavender, and bought her first 18 babies at the Sequim Lavender Festival yesterday.
