Backflow can be considered the change in direction of the normal flow of water in a system. Back flow preventers are devices that help to stop this back flow from contaminating the drinking water in the home. Backflow can be a problem in a water system because it can spread contaminated dirty water through the water supply system.
Backflow can occur at cross connections. A cross connection can be anywhere there is the potential of contaminated water mixing with potable or drinking water. Negative health effects can occur if the contaminated water is ingested. We will be looking for back flow flow preventers while performing your New Jersey home inspection..
Backflow occurs under two conditions:
Back pressure is the reversing of regular water flow direction within a supply system caused by down-stream pressure being higher than the pressure in supply. The reduction in supply pressure can occur when the amount of water being used exceeds the amount of water being supplied. This decrease in supply can occur when a water main breaks for example.
Back siphon is the reverse from regular flow direction within a supply system that is caused by negative pressure in the supply piping. This is the reversal of regular flow cause by a vacuum with in the supply pipes themselves. Back-siphon can occur when there is a high water flow in a pipe line, when there is a line break that is lower than the service point, or when there is lower main pressure caused by high-water flow rates.
Atmospheric Vacuum Breakers:
Backflow prevention in residential homes is accomplished through the use of vacuum breakers. Vacuum breakers allow air flow into a pipe so that a siphon can not take place. Vacuum breakers are small, simple and inexpensive devices that require little maintenance.
Requirements of vacuum breakers:
- The vacuumed breaker must be at least 6 inches above any higher point downstream of the device.
- The vacuum breaker cannot be installed in an enclosure containing air contaminants. If contaminated air enters the supply piping, it can contaminate the drinking water supply.
- A shut off valve should never be installed downstream of the vacuum breaker, to avoid continuous pressure on the vacuum breaker.
- Vacuum breakers should not be subject to constant pressure for more then 12 hours in any 24 hour time period or they can fail.
- Leaking of water from the top of the vacuum breaker is an indication that the breaker has failed and needs replacement.
Types of Backflow Presenter Assemblies
The appropriate type of backflow preventer used for any given application will vary depending on the potential hazard. The primary types of backflow preventers are:
- Double check valves: These are commonly used in raised tanks. Double check-valve assemblies are effective against backflow caused by back-pressure and back-siphon and are used to protect the potable water system from low-hazard substances.
- Reduced pressure principle assemblies: These are commonly used in industrial plants, hospitals, chemical plants, boilers, and fire sprinkler systems. Reduced pressure principle assemblies protect against back-pressure and back-siphon of pollutants and contaminants. The devise is comprised of two internally loaded, independently operating check valves with a mechanically independent, hydraulically dependent relief valve between them.
- Pressure vacuum breakers: These are commonly used in industrial plants, cooling towers, laboratories, laundries, swimming pools, lawn sprinkler systems, and fire sprinkler systems. Pressure vacuum breakers use a check valve that closes with a spring when water flow stops. Its air-intake valve opens when the internal pressure is one PSI, preventing non-potable water from being siphoned back into the potable system.
Backflow presenters are designed to prevent the reverse flow of water in a clean water system. There are several types of backflow preventers each one has a different purpose.
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