Garden hoses can be a hazard to the homeowner and public drinking water supply. The danger comes when the hose - any hose - is connected to a harmful substance without proper protection. This is called a "cross connection." If the pressure in the city's water main drops while your hose is submerged in polluted or contaminated water, then the water (and whatever is in it) could flow in the opposite direction, back into your water pipes and into your drinking water supply. This backwards movement of water is called "backflow," and can occur when your hose is not protected with a backflow protection device. Water pressure drops are not uncommon. They can happen when fire fighters are fighting a nearby blaze or before a city crew repairs a broken water main.
Preventing Cross Connections
Cross connections can cause serious problems. Contaminated drinking water can cause sickness and even death. However, this can be avoided by using a backflow prevention device, called a "hose-bibb vacuum breaker" at each outside faucet.
An unprotected hose with the faucet turned on and the spray nozzle turned off is under pressure. The hose can expand and contract due to the temperature and pressure changes. This can cause the water inside your home to taste bad and possibly make you ill due to the chemicals from the hose that flow back into your drinking water.
Fortunately, keeping your water safe from harmful substances is easy. Take the following precautions to protect your drinking water:
Never submerge hoses in buckets, pools, hot tubs, sinks, sewer lines, or a car's radiator.
Always give the end of the hose at least 2 inches of air space above the container!
Do not leave your hose faucet on when you are not using it.
Do buy and attach a low-cost hose-bibb vacuum breaker device for all of your outdoor faucets to prevent backflow. They are available at hardware stores.