What is a cross connection?
A cross-connection is any temporary or permanent connection between a public water system or consumer's drinking water system and any source or system containing non-potable water or other substances.

What is backflow?
Backflow is the undesirable reversal of flow of non-potable water or other substances through a cross-connection and into the piping of a public water system or consumer's portable water system. There are two types of backflow--backpressure backflow and back siphonage.

Backpressure backflow
Backpressure backflow is backflow caused by a downstream pressure that is greater than the upstream or supply pressure in a public water system or consumer's potable water system. Backpressure (i.e., downstream pressure that is greater than the potable water supply pressure) can result from an increase in downstream pressure, a reduction in the potable water supply pressure, or a combination of both. Increases in downstream pressure can be created by pumps, temperature increases in boilers, etc. Reductions in potable water supply pressure occur whenever the amount of water being used exceeds the amount of water being supplied, such as during water line flushing, fire fighting, or breaks in water mains.

Back siphonage backflow
Back siphonage is backflow caused by a negative pressure (i.e., a vacuum or partial vacuum) in a public water system or consumer's potable water system. The effect is similar to drinking water through a straw. Back siphonage can occur when there is a stoppage of water supply due to nearby fire fighting, a break in a water main, etc.

What can cause backflow?
JMWSC may have to shut off a water main to make repairs. This may cause a drop in water pressure allowing the customer's water to flow back into the public water distribution system. Sometimes the customer has a pump downstream from the water meter which could override system pressure and pump water back into the distribution system.

How can I prevent backflow?
PROBLEM:
The water hose attached to fertilizer, pesticide or sprayer could contaminate your water supply. You can reduce the risk of contamination by shutting off the water supply to the hose at the faucet when you are finished. Even if the hose has a nozzle attachment, any decrease in pressure could back siphon the water from the hose, bucket or sprayer back into your plumbing system.
SOLUTION:
Purchase a hose bib vacuum breaker from any hardware store that will prevent contaminates from entering the plumbing system.

PROBLEM:
A hose left in a bucket used for cleaning.
SOLUTION:
Remove the hose from the bucket (or sink) and shut off the water at the tap.

PROBLEM:
Underground irrigation systems are one of the types of cross connections posing a health hazard to the public drinking water system. Contamination from herbicides, pesticides and animal droppings can enter your irrigation system when below ground sprinkler heads are used.
SOLUTION:
Installation of a Double Check Valve Prevention Assembly. This device can prevent back pressure or a back siphonage condition. NOTE: Starting July 2004, JMWSC requires all new residential meters with or without irrigation be equipped with a double check valve assembly.