What is a cross connection?
A cross connection is a connection between two separate water systems that could cause contaminants to enter the water you drink. These connections are present in all homes and businesses.
Why it matters at home
By far the most common sources of cross connection contamination found in homes are garden hoses and irrigation systems.
If you connect a hose to a sprayer to apply a pesticide or fertilizer, or submerge the end of a hose within a pool, hot tub or bucket of soapy water to wash your car, you could be introducing contaminants into your household water supply.
Even if the hose or sprinkler head is not directly connected to a pesticide or fertilizer, it may have previously been submerged in standing water in your yard where chemicals or animal waste was present.
Common risk setups
Hose-end sprayers, submerged hoses in pools/hot tubs/buckets, irrigation heads sitting in standing water.
How backflow happens
Under normal pressure conditions, water flows in one direction — from our network of water mains into your home. Under certain conditions, the flow can be reversed, causing water and other substances to flow back into your home through your indoor plumbing.
This can be caused by backpressure (pressure in your home exceeds pressure coming in from a public water main) or backsiphonage (pressure coming into your home decreases significantly due to a nearby water main break or a significant spike in water use for firefighting purposes).
What you can do
For a very inexpensive means of protection, install hose bib vacuum breakers on all outside faucets. These devices, which can be purchased at most home supply stores, are designed to allow water to flow in only one direction.
Or, for an additional level of security, install an approved, testable backflow prevention assembly. Either SCWA or your plumber can assist you with choosing the right one.
- Install hose bib vacuum breakers on all outside faucets
- Consider a testable backflow prevention assembly for added protection
- Avoid leaving hoses submerged in pools, buckets or standing water
Commercial facilities
SCWA maintains a program to ensure water from commercial facilities does not enter the public water supply. We require all commercial facilities where a potential hazard exists to install an approved backflow prevention device.
While residential backflow prevention is not mandated by law, for the reasons stated above, we hope you’ll take the necessary steps to protect your water supply.
Keep in mind that in addition to garden hoses and irrigation systems, household backflow can be caused by fire suppression systems, geothermal systems and chemically-treated boilers.