Domain 5
Water Quality
Source testing, treatment selection, and plumbing material choices recorded with results.
What this domain covers
This domain starts by testing the water that actually arrives at the property, before anything is chosen to treat it. A utility's annual report describes the source water, not the service line and not the house, so it does not satisfy the requirement. A private well or a rainwater supply is tested regardless.
From that laboratory result the domain covers what the water must meet at the drinking tap, the treatment selected against the result rather than against a catalogue, the material the supply piping is made from, fixtures and fittings in contact with drinking water, softening and what it may and may not be described as doing, the flushing carried out before handover, and the service intervals every device depends on.
Why it matters in Central Texas
The Austin–San Antonio corridor sits over aquifers with real and well-documented variation in what they carry, and private wells in Texas are not tested by any agency on the owner's behalf. Where the ground is karst, water moves through it far faster than through granular aquifers, so what happens some distance away is not as distant as it looks.
Public supply here is drawn largely from surface water and disinfected, which is a configuration that forms treatment byproducts. None of this is a reason for alarm; it is the reason the Standard tests the specific property rather than reasoning from the region.
How depth is chosen
All three rungs are available. Essential is the floor: a laboratory test at the property before design, a documented flushing protocol, treatment at the drinking taps selected against the result, certified devices with their service intervals written into the Record, and rules governing softening.
Enhanced adds whole-house filtration chosen against the same laboratory result. Comprehensive adds remineralisation to that whole-house system and takes drinking-water fixtures to materials verified against their certificates. Treatment can be added later; the choice of distribution material cannot.
What we document
The Record holds the laboratory report with its chain of custody, sample point and date; the post-installation result sampled at each drinking tap with the laboratory's stated reporting limits printed on it; the certification listing for every device; the flushing protocol with its volumes and dates; and the service interval for each piece of equipment, handed to the family at handover.
The laboratory and an independent verifier do the checking. Treatment is judged by what reaches the tap, not by the presence of a device.
Findings in this domain are recorded in the Sage Co. Record. Sage Co. may mark a requirement specified and installed. Only an independent third party can mark it verified, and verification is elected domain by domain — how verification works.
Reviewed by Jake Rangel, September 19, 2026
Related reading
- Trihalomethane exposure in drinking water measured against bladder cancer in a pooled analysis of six case-control studies
- Blood lead concentration measured against intellectual function in a pooled analysis of seven cohorts
- Drinking water contaminant release and odor measured across six PEX pipe brands and a six-month-old PEX plumbing system
- Review of drinking water nitrate and health outcomes reported in an updated epidemiologic review
- Review of arsenic in drinking water reported in a National Research Council subcommittee update
- Review of fluoride in drinking water reported in a National Research Council committee assessment
Build this into your house
Sage Co. builds and consults across Austin, San Antonio and the Hill Country. Start with a call and we will walk this domain — and the other ten — against your project.