I am reading the "Installation Manual for Viega PureFlow Water System" and on page 41 it states:
Do not install Viega PureFlow PEX tubing where soil is or may become contaminated with solvents, fuels or similar chemicals.
AND
Do not install tubing above or below septic tanks, leach fields, pits, or cesspools.
Why?
Best Answer
Basic cross-contamination protection. Same basic idea of not putting the latrine upstream of the drinking water intake, or more pithy sayings I can't say here as they refer to human food byproducts by pithy rude names.