Anti-Siphon Valve vs Backflow Preventer – What is the Difference?

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    Protect your water supply and ensure good water flow with a backflow preventer or an anti-siphon valve. However, which one do you pick? Understanding both the anti siphon valve and backflow preventer can help you deal with this dilemma. Continue reading to understand the difference. 

    Difference Between an Anti-Siphon Valve and a Backflow Preventer

    A backflow preventer represents a term covering mechanisms that ensure water does not reenter a public water supply system once sent via an irrigation system. Anti-siphon valves represent one-way valves that allow water to flow in only one direction. An anti-siphon valve represents a specific kind of backflow preventer covered under the subcategory of the term ‘backflow preventer.’

    Although this may seem confusing, a deeper look at the two terms will help differentiate them better.

    Backflow Preventer

    Backflow preventers protect the public water supply system from becoming contaminated. Widely used in irrigation systems, it prevents soil and other impurities from contaminating the public water supply.

    All irrigation systems need at least one backflow preventer to ensure a clean water supply. Without a backflow preventer, the negative pressure in the water supply system may result in pesticides and fertilizers seeping into the water. 

    Uses of Backflow Preventers

    Backflow preventers generally find use in irrigation systems and places where you connect a tap to a hose. Different states provide their codes for backflow preventer installations. Read the codes for a better understanding of municipal ordinances. ‘Cross-connection control’ in the codes usually indicates backflow prevention.

    Anti-siphon Valve

    Anti-siphon valves represent a specific type of backflow preventer used commonly in residential water supply systems. Easy to install and inexpensive, they represent one of the most popular backflow preventers. 

    Anti-siphon valves function with the help of an in-built atmospheric vacuum breaker. This atmospheric vacuum breaker stops the suction that results in contaminated water seeping into residential water systems. 

    Limitations of Anti-siphon Valves

    Although anti-siphon valves remain one of the most popular backflow preventers, they come with several limitations. These constraints prevent them from being used everywhere. Below are some of the limitations of anti-siphon valves:

    • Anti-siphon valves, usually installed six inches above the ground, do not work well for underground irrigation systems
    • Requires direct connection with a water source
    • Backflow preventers (or a check valve) installed upstream to prevent the installation of other anti-siphon valves downstream
    • Certain cities provide building codes disallowing the use of anti-siphon valves
    • You cannot install anti-siphon valves in areas submerged underwater

    Which Type of Backflow Preventer Suits Me Best?

    Talk to the irrigation specialist setting up your home’s water supply system to determine the type of backflow prevention you require. Usually, these individuals come well versed in local ordinances and can help you decide which type of backflow preventer suits your irrigation system better especially if the lines are part of the potable water supply. 

    You can also examine the different types of backflow prevention devices to find out what purpose each serves. Once you decide about the device you need, check the local ordinances for those permitted for use in your locality. 

    Our Final Say

    Anti-siphon valves and backflow preventers both work to keep your water supply clean and uncontaminated. Whereas anti-siphon valves prove ideal for residential use, backflow preventers serve public water systems better. Some municipalities take serious action against contaminated water. This reason makes these devices a must for every household or irrigation system.

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