Prevalence of Cross-Connections in Household Plumbing

The USC Foundation received a grant in 2001 from the United States Environmental Protection Agency to assess the prevalence of cross-connections in household plumbing systems.

On-site surveys were conducted in 188 homes in the US Mid West. The data was analyzed to determine how many cross-connections existed in the homes. Additionally, it was determined if the cross-connections were direct or indirect and if the cross-connection constituted a health hazard or a non-health hazard.

homes surveyed
health hazard
cross- connection

survey homesPCCHP House


The surveys indicated that 9.6% of the homes were found to have direct cross-connections to a health hazard. On average, 73% of water use was unprotected, constituting cross-connections. Only 4.3% of the homes had either no unprotected cross-connections or had unprotected cross connections to a non-hazardous substance.

Homes with a cross-connection (either direct or indirect) to a health hazard constituted 95.7% of the homes. Although this is a large percentage, the greatest concern was with the 9.6% of the homes having a direct cross-connection to a health hazard.

In most cases, these cross-connections were due to improperly plumbed toilet fixtures, or specific toilet fixtures that could create a backpressure situation and force hazardous water from the toilet tank into the drinking water supply.

Most of the residents were completely unaware of what cross-connections were or what could be done to prevent them. When the on-site survey was conducted, the residents were given a brochure describing typical household cross-connections and what could be done to abate them. It would appear that further study would be needed to get a better overall picture of household cross-connections.

Even without further study, however, it is evident that better public education is necessary. Public education for the homeowner or resident would go a long way in helping to reduce the problem of cross-connections in the home.

Cross-Connections in
Household Plumbing Brochure

The illustrated brochure uses illustrations of common plumbing fixtures like a toilet and sink to explain where cross-connections may be found and how to protect them from possibly contaminating the water supply. Click HERE to order today!

Cross-Connections in Household Plumbing Brochure


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Impacts of Cross-Connections in NOrth American Water Supplies