09/09/2026
Why Outdoors & Above-Ground Is the Best Option ๐
"๐๐ฎ๐ป'๐ ๐๐ฒ ๐ท๐๐๐ ๐ฝ๐๐ ๐ถ๐ ๐๐ป๐ฑ๐ฒ๐ฟ๐ด๐ฟ๐ผ๐๐ป๐ฑ?" is the first question most building owners ask. For reduced pressure zone (RPZ) assemblies, the answer is a resounding no. Every manufacturer of ASSE-approved RPZs in the U.S. prohibits below-grade installation. RPZs are designed to discharge water when check valves fail, and that discharge has nowhere to go in a vault.
"๐ช๐ต๐ฎ๐ ๐ฎ๐ฏ๐ผ๐๐ ๐ถ๐ป๐๐ถ๐ฑ๐ฒ ๐๐ต๐ฒ ๐ฏ๐๐ถ๐น๐ฑ๐ถ๐ป๐ด?" That option trades one problem for a worse one. A 3-inch RPZ can discharge water at a rate that overwhelms any standard floor drain. Case studies from commercial buildings show that indoor RPZ failures have caused catastrophic flooding at costs far exceeding the price of an outdoor enclosure.
"๐ช๐ฒ'๐๐ฒ ๐ฎ๐น๐๐ฎ๐๐ ๐ฑ๐ผ๐ป๐ฒ ๐ถ๐ ๐๐ต๐ถ๐ ๐๐ฎ๐" is the most common reason outdated methods persist. While it may be difficult to change course, Las Vegas found it could save up to $60,000 per installation by switching from underground vaults to above-ground aluminum enclosures. This proves the change is worth it. Cities like Portland, Arlington, the state of New Jersey and dozens of other water jurisdictions have since updated their standard details to require above-ground enclosures entirely.