The Color Purple: Protecting Against Cross-Connections from Wastewater

By Don Vandertulip, P.E.
Principal, CDM

Many individuals who follow industry developments are aware of revisions to the Uniform Plumbing Code (UPC) published by the International Association of Plumbing and Mechanical Officials (IAPMO) (see my 12.08 blog for background) that now require use of purple pipe on private property plumbing to convey any non-potable water. The International Plumbing Code (IPC) distributed by the International Code Council (ICC) has similar requirements. WEF’s primary objection to use of purple pipe for onsite non-potable water is the risk to the public through exposure to untreated water. A secondary concern is loss of public confidence in the highly treated reclaimed water distributed in purple pipe by municipal utilities. (Read about recommendations and a letter to IAPMO.)

Simply put, cross connections between a potable water system and any non-potable water supply places the public at risk. The potential for cross-connections with multiple onsite coded non-potable pipe systems proposed by IAPMO could result in a more serious cross connection with the potable water system. I caution all professionals not to think of the onsite alternate piped water as non-potable water but to treat it as wastewater, which includes graywater as it’s generally defined -- all wastewater generated onsite except toilet waste. In many jurisdictions, graywater excludes kitchen sink and dishwasher washwater due to the high organic content of food waste. The key word is "wastewater". In most cases, graywater is not treated though there may have been a lint filter originally provided.

In addition to the potential cross connection of one or more onsite wastewater sources with the potable water system, there is potential for contamination of the highly treated municipal reclaimed water system. Contamination of a municipal reclaimed water system by one of the onsite wastewater systems could result in exposure of individuals with incidental contact to reclaimed water of impaired quality. This exposure could result in illness, even if the reclaimed water were not ingested. Degradation of the reclaimed water quality could also negatively impact other municipal reclaimed water users and violate the user agreement between the utility and customer. I suggest that the untreated wastewater proposed for recirculation and use onsite without treatment does not yet rise to the caliber of "non-potable" until it has received enough treatment to transition from its wastewater designation. In short, distributing wastewater onsite in a purple plumbing pipe will eventually cause significant damage to our collective reclaimed water programs and jeopardize public health.