PEX and PP Water Pipes: Assimilable Carbon, Chemicals, and Odors
Bibliographic record
Abstract
Eleven brands of plastic drinking water pipe were evaluated for assimilable organic carbon (AOC) release at 23°C for 28 days: polyvinyl chloride, high‐density polyethylene, polypropylene (PP), and cross‐linked polyethylene (PEX) pipes. Three of eight PEX pipe brands exceeded a 100 µg/L AOC microbial regrowth threshold for the first exposure period, and no brands exceeded this value on day 28. No AOC increase was found for PP or PEX‐a1 pipes; the remaining pipe brands contributed marginal AOC levels. Pipe water quality impacts were more fully evaluated for two PEX‐b brands and one PP brand. PEX pipes caused greater odor than the PP pipe and released more organic carbon as well as volatile and semi‐volatile organic compounds. Water quality impacts were less after 30 days. Regulated and unregulated contaminants were found in three PEX plumbing systems. Drinking water odors were attributed to toluene, ethyl‐tert‐butyl ether, and unidentified contaminants.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".