How Contamination Occurs
Water normally flows in one direction, from the public water system through the customer’s cold or hot water plumbing to a sink tap or other plumbing fixture. The plumbing fixture is the end of the potable water system and the start of the waste disposal system. Under certain conditions water can flow in the reverse direction. This is known as backflow.
Backflow occurs when a backsiphonage or backpressure condition is created in a water line. Backsiphonage may occur due to a loss of pressure in the water distribution system during a high withdrawal of water for fire protection, a water main or plumbing system break, or a shutdown of a water main or plumbing system for repair. A reduction of pressure below atmospheric pressure creates a vacuum in the piping. If a hose bib was open and the hose was submerged in a wading pool during these conditions, the non-potable water in the pool would be siphoned into the house’s plumbing and back into the public water system.
Backpressure may be created when a source of pressure, such as a pump, creates a pressure greater than that supplied from the distribution system. If a pump supplied from a non-potable source, such as a landscape pond, were accidentally connected to the plumbing system, the non-potable water could be pumped into the potable water supply.
How to Prevent Contamination of Your Drinking Water
Protect your drinking water by taking the following precautions:
- Submerge hoses in buckets, pools, tubs, sinks, ponds, etc.
- Use spray attachments without a backflow prevention device.
- Connect waste pipes from water softeners or other treatment systems to the sewer, submerged drain pipe, etc.
- Use a hose to unplug blocked toilets, sewers, etc.
- Keep the ends of hoses clear of all possible contaminants.
- If not already equipped with an integral (built-in) vacuum breaker, buy and install hose bib type vacuum breakers on all threaded faucets around your home. These devices are inexpensive and are available at hardware stores and home improvement centers.
- Install an approved backflow prevention assembly on all underground lawn irrigation systems. Remember, a plumbing permit is required for the connection of an underground lawn irrigation system to your plumbing system.
Hose Connection Vacuum Breaker
Hose connection vacuum breakers are specifically made for portable hoses attached to hose thread faucets. Their purpose is to prevent the flow of contaminated water back into the drinking water. These devices screw directly to the faucet outlet. They can be used on a wide variety of installations, such as service sinks, hose faucets near a wading pool, laundry tub faucets, etc. Some units are designed for manual draining for freezing conditions. Some are furnished with breakaway set screws as a tamper proof feature. These devices are not intended for operation under continuous pressure.
Protection of the North Weld County Water District’s Distribution System
In general, the installation of plumbing in compliance with the plumbing code will provide adequate protection for your plumbing system from contamination. However, the District may require (as a condition of service) the installation of a backflow prevention assembly on the water service to provide additional protection for the public water system. A backflow prevention assembly will normally be required where a single-family residence has special plumbing that increases the hazard above the normal level found in residential homes, or where a hazard survey cannot be completed.
Common Household Hazards
Chemical Spray Applicators
The chemicals used on your lawn and garden can be toxic or fatal if ingested. These chemicals include pesticides, herbicides, and fertilizers. Even strong cleaning chemicals sprayed on cars, house siding, etc., may cause health problems if ingested.
Water held in pools, ponds or other vats open to the air and exposed to humans or animals may contain microbiological contaminants.
Hoses submerged in buckets or containers can act as a conduit for contaminants under backflow conditions.
Underground Lawn Irrigation Systems
Underground irrigation systems often have puddles of standing water around the ground level sprinkler heads. The sprinkler heads are not designed to be drip-tight under backflow conditions. The puddles of water may contain microbiological contaminants, such as excrement from animals or chemical residue from fertilizer and herbicides sprayed on the lawn.