Water Systems & Plumbing

Water is the second-most expensive system in a new build after the envelope, and it's the one most likely to cause damage if it's done wrong. Well, septic, plumbing supply, drainage, vapor barriers, and bulk-water management all interact — a vapor barrier on the wrong side of the wall and a poorly graded site can do more damage in five years than a hurricane. For owner-builders going semi- or fully off-grid, water also includes capture, storage, and reuse, which most code officials won't help you plan.

The technical decisions cluster around three questions. Where does your water come from (municipal, drilled well, dug well, rainwater)? Where does it go after you use it (sewer, septic, greywater diversion)? And how do you keep it out of places it shouldn't be — wall cavities, crawl spaces, slab edges? The EPA's SepticSmart program covers conventional disposal well; rainwater capture and greywater reuse are governed locally and vary widely by state and province.

Recommended starting points:

• Vapor barrier installation — which side of the assembly, which permeability rating, which climate.
• Composting toilet rules by state — the regulatory layer most people don't research before buying one.
• Greywater systems — capture, treatment, and reuse for landscape irrigation.

The pitfall to internalize: bulk water always wins. No vapor retarder, no air barrier, and no insulation system can compensate for water that's getting in. Roof overhangs, drainage planes, capillary breaks, and site grading do more for long-term durability than any product you'll buy. Building Science Corporation has been making this point for thirty years, and it's still the single most ignored piece of advice in residential construction.