A backflow preventer is essential to protect your family, the house, your neighbors and the environment.
Heavy rain, flash floods, or water main breaks and maintenance, are just some of the reasons you need a backflow device or assembly.
Lawn sprinklers require backflow preventers, but knowing what you need is complicated. Relax, In this Plumber Near Me USA article I will explain it all.
Table of Contents
What Is A Backflow Preventer? Do I Really Need A Backflow Prevention Device?
Cross-Connections Require Backflow Preventers
Before we can answer the question “What is a backflow preventer?” we need to understand cross connections.
In a plumbing system, a cross-connection is a point where the drinking (potable) water supply is connected to water that is not intended for drinking (non-potable). There are two kinds of cross-connections: indirect and direct.
A direct cross-connection is when a pressurized non-potable (non-drinkable) waterline is connected to a potable (drinkable) water system. So, that includes, some fire sprinklers, boiler lines, irrigation lines, pipes used to move or inject chemicals, etc.
An indirect cross-connection is a when a hose or line that is open at one end is connected to a potable water system. Indirect cross-connections are made when lawn sprinkler systems, garden hoses, bathtubs, water softeners, sinks, washing machines, showers, etc. are connected to the potable water system.
What Are Backflows?
A backflow is the unwanted reversal in the flow of water, or other liquids, solids or gasses. This happens via a cross connection into the consumer’s potable water system, or the public water system.
A backflow causes water, solids, liquids, or gasses from any source to flow back into the potable water supply. Backflow is caused by either Backpressure or Backsiphonage. To prevent this, a backflow prevention device is required.
What Is Backpressure And What Causes It?
Backpressure is caused when the water pressure in the house or business is higher than the pressure in the water supply’s piping. The increased pressure may be caused by a heating boiler, booster pump, etc. The scenario below describes how backpressure could cause backflow in a water system:
- A homeowner installs a lawn irrigation system that is supplied with water from a pond via a pump operating at 30 psi. To ensure there is still water for the irrigation system when the pond is empty, the homeowner installs a standby connection to the household’s plumbing.
- The fire department uses water from a fire hydrant and this causes the public water system’ pressure to drop from 50 psi to 20 psi.
- On the day when this happens, the valve between the irrigation system and the household plumbing that is normally closed, is left open accidentally.
- Normally, there won’t be any backflow as the pressure supplied by the irrigation pump is less than the pressure in the public water system. However, when the fire hydrant is used, the pressure in the water main is less than the pressure from the irrigation pump. This results in water from the pond being pumped into the public water system via the household plumbing.
- When the hydrant is closed, the pressure in the public water system increases. Resulting in contaminated water being delivered to customers that use the system.
What Is Backsiphonage and How Does It Happen?
Backsiphonage causes backflow due to negative pressure (partial or full vacuum) in the (city) supply piping. Backsiphonage happens when the system pressure drops to less than atmospheric pressure. This causes an effect much like sucking water through a straw.
The scenario below describes how backsiphonage could cause backflow in a water system:
- A public water system main at the bottom of a hill is closed off to repair a leak.
- As the homes on the hill are at a higher elevation than the water main, water in the plumbing from the homes on the hill drain into the public water system main when water is used by homeowners at the bottom, as this creates a siphon at households at the top of the hill.
- A garden hose is being used to fill a wading pool at a household at the top of the hill and the hose is submerged in the pool’s water.
- When the backflow condition is created, the non-potable water from the wading pool is siphoned through the submerged hose (cross-connection) into the city water main via the household plumbing.
- The wading pool water contaminates the city water main and this water is delivered to customers using the public water system when water service is restored.
How To Prevent Cross-Connections
Keeping our drinking water safe from contaminates is easily achieved by following these simple steps:
- Understand what it is and avoid Cross-Connections where possible.
- Install approved Backflow devices, assemblies, or air gaps on systems that contain contaminated water.
- Install a hose bib backflow preventer on water fixtures. Without being protected properly, even a garden hose could potentially contaminate the water supply in your home. The American Backflow Prevention Association estimates that more than 50% of the country’s Cross-Connections consist of unprotected garden hoses.
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Methods of Backflow Prevention
Backflow can easily be prevented in various ways. The first of which is the installation of an approved air gap (AG). Which provides a physical separation between the drinking water supply and the contaminant.
The second method is by using a backflow prevention device. Which is a mechanical device or assembly that will prevent backflow from happening.
Household plumbing systems commonly use air gaps (AGs) to prevent backflow. These are typically used in household bathrooms and kitchens.
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The physical separation between the kitchen sink rim and kitchen faucet is an example of an approved AG. As is the physical separation between a bathroom faucet and the rim of a sink or bathtub.
Current plumbing codes specify that all bathtubs and sinks sold in the U.S. must have approved AGs built in to prevent household plumbing from becoming contaminated.
Mechanical Assemblies and Devices
Apart from AGs, there are various mechanical means that can be used to prevent backflow. These could be anything from a single check valve to an elaborate approved assembly to prevent backflow.
When installed properly and maintained, all these mechanical devices and assemblies will avert backflow at some level. However, not all mechanical devices and assemblies are equal to the task. Various models will provide varying levels of backflow protection.
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Some of these have been designed to only prevent backsiphonage backflow. Which means that they will not be effective to prevent backflow caused by backpressure. While others have been designed to prevent backflow caused by both backpressure and backsiphonage.
When a backflow preventer is selected to protect the city water system, care should be taken to ensure that the preventer is suited for the backflow conditions likely to occur for the relevant scenario.
Backflow preventers should correspond to the level of health hazard (high versus low) posed to the public water system.
For example, some backflow preventers are manufactured to very high standards, and will therefore be more reliable than devices manufactured to lower standards in preventing backflow. In high hazard cross-connection scenarios, higher reliability assemblies should be used to prevent backflow.
Backflow Preventers: Devices and Assemblies
An important differentiator between backflow preventer types is whether the design allows for them to be repaired and tested while installed. In-line testing is done to determine whether the preventer is functioning properly to prevent backflow.
Preventers that can’t be tested while installed are known as devices. While preventers that can be tested and repaired while in-line, are known as assemblies. Assemblies include test cocks and isolating valves for testing purposes.
Another difference between backflow preventer types is whether they can isolate the city water distribution system from the homeowner’s plumbing. This notion is known as premise isolation.
Premise isolation assemblies are normally situated at the property line or water meter. Some assemblies can be used to only prevent backflow at fixtures, while others are used for premise isolation.
The notion of installing a backflow preventer at fixtures, such as boilers, is known as fixture protection. When choosing a backflow preventer for a specific scenario, the preventer’s purpose should be considered, i.e. is it to be used for fixture protection or premise isolation.
Sewer Backflow Valves
The video below by the Insurance Bureau of Canada shows how backflow valves work, and how they are installed.
Basements may have problems with water backup whenever there’s been a lot rainfall. Heavy rainfall can overflow the city sewer system. If pure rainwater floods your basement, that’s bad enough. However, we’re talking about raw sewage flooding the house. Fortunately, this can be prevented by the installation of a backflow valve.
What Is A Sewer Backflow Valve?
A sewer backflow preventer, sometimes known as a sewer backwater valve, is installed in a sewer line. Its purpose is to permit sewage or water to only flow in just one direction, i.e. away from your home.
Whenever there is heavy rain, the city’s sewer lines could become overloaded. This can cause sewage or dirty water to flow into homes. If you have a backflow valve installed and the sewer system backs up, the sewage won’t be able to backflow into your home.
Some municipalities require backflow valves, while others recommended them. They can be fitted into existing houses, or installed during any new construction.
It is much cheaper to install these during the initial construction. It will typically cost between $50 and $250, depending upon whether it has a viewing lid or not.
Concrete will have to be cut or chopped out to allow the main sewer line to be accessed when retrofitting. Backwater valves typically cost between $1,000 and $2,000 to retrofit. Some municipalities offer subsidies to help with installing back flow valves.
If your home’s floor is less than one foot higher than street level, or if you have a basement, the risk of water backup increases. The National Plumbing Code requires that a backwater valve has to be installed in new homes with fixtures located below street level.
How Do Backwater Valves Work?
A sewer system lets sewage and water flow away from buildings. Backwater valves prevent sewage and water from flowing back into the building in the event the main sewer lines become overloaded. You can normally check if a backwater valve is working correctly by looking through a clear cover over the backwater valve’s access box.
The valve contains a small flapper that’s open under normal conditions to allow the water to flow away from your home. It also lets sewer gases vent. On each side of the flap, there is a small float. If sewage or water flows back from the sewer system, these floats push the flap up and closes it. Thereby preventing any water or sewage from flowing back into the building.
When sewage does not come back to the building anymore, the flap will drop to the open position due to gravity, and sewage and water can flow out of the building again.
If a backwater valve is installed in an existing building, a plumbing permit will be required from the municipality.
A qualified, local plumber will cut or chop a hole in the floor’s concrete, normally close to the drain in the floor, and excavate down to the sewer line. They will then remove a section of pipe, and install the new backwater valve.
Better quality backwater valves normally have a transparent top for visual inspection of correct operation. There is also a lid that can be opened in the event that cleaning is required.
Without a backwater valve that is installed and positioned correctly, sewage may enter a basement via sinks, floor drains, washing machines, toilets and tubs.
What to Do When The Crap Hits The Floor
Normally, you won’t experience any problems if you have a backwater valve that has been installed and positioned properly. That is, providing it has been maintained properly. However, the valve can be damaged by sharp objects. Or things may get stuck, and this can prevent a valve from closing properly.
Regular, proper maintenance should identify these issues before they cause serious problems. It is normally easy to access backwater valves, and you can see through the clear top if anything has gotten stuck, or if water is not flowing freely.
Contact a plumber if you don’t want to stick your hand down the sewage pipe. If you do try to fix problems on your own, follow ALL relevant instructions carefully. Also, make sure you wear gloves.
If everything is working as it should, your backwater valve will close if the main sewer backs up due to heavy rain. While the valve is closed however, water can’t flow away from the building.
Although there should be some extra space in a plumbing system to cater for this, you may think about not showering or running your dishwasher and washing machine simultaneously during heavy rain, or during a period when lots of snow is melting. As none of the water will flow from your house while the backwater valve is shut, you may end up causing a flood in your own home.
Selecting a Lawn Sprinkler Backflow Preventer
Your sprinkler system should have an irrigation backflow preventer if the water for the system is taken from a drinkable water source. In many places it is a legal requirement that your irrigation system has a backflow preventer on that is approved by the local authority if your irrigation water source is deemed potable.
For non-potable water sources, it is generally not a legal requirement to have a backflow preventer fitted. This is however not always the case. Some local authorities require backflow preventers for water that is not potable, such as gray, reclaimed, and recycled water sources.
Backflow preventers come in many different types. Almost all local authorities specify the backflow preventer types irrigation systems may NOT use. In some instances, the local authorities will specify the exact backflow preventers that MUST be used.
Cross-Connections have been described earlier in this article. Backflow preventers are nearly always installed at cross-connections to prevent the potable water from becoming contaminated.
What Is Potable Water?
Potable water is simply water that is suitable to drink. This may include drinking water for animals, depending on local regulations. If you are willing to drink water from a source without treating it, it’s probably considered to be potable.
Water not suitable for drinking is known as non-potable water. Also, water is classified as non-potable once it has entered into an irrigation system.
Water that is deemed non-potable includes stream water, pond and lake water, as well as well water from contaminated aquifers that should not be drunk. A backflow preventer is required for most other wells, even if water from the well is not used for drinking.
This is done to shield the aquifer where the well gets water from. As even if drinking water is not taken from the well, others may use the same aquifer to get drinking water.
Irrigation systems used with pesticides or fertilizers have to have a backflow preventer, irrespective of where the water comes from. Those chemicals should definitely not go into the water table, streams or lakes!
Are Lawn Irrigation Backflow Preventers Needed?
“Section 608.16.5, of the International Plumbing Code and Section P2902.5.3 of the International Residential Code (connections to lawn irrigation systems), states that the potable water supply to lawn irrigation systems shall be protected against backflow by a pressure-type vacuum breaker, a double-check valve assembly or a reduced pressure principle backflow preventer – depending on the degree of the site hazard.”Forest Lake MN Backflow Prevention FAQs
There are a lot of smart people with dumb ideas about backflow preventers. Perhaps, because there are so many kinds of preventers with different capabilities. The fact remains that backflow prevention is really necessary.
Irrigation water is legitimately classified as a contaminant, i.e. it can create health hazards, rather than a pollutant, i.e. is offensive in odor or color. Irrigation water contains toxic chemicals like pesticides and fertilizers, and animal waste. So, if you don’t stop them, these elements can and will push back into drinking water via irrigation pipes.
If a well is used as the water source, the chemicals flow into the well and then move into other people’s drinking water. If community water systems are used, they could get in the pipes and poison others using the same system. It is not sufficient to rely on the irrigation system’s valves that are used turn it off and on to prevent backflow.
Backflow preventers provide protection when the valves leak or break, which eventually happens to all valves. It is not worthwhile to save some money by not installing a backflow preventer. Only to later be faced by medical bills for poisoned family members or pets!
It is commonly argued that backflow preventers are not required as water can’t flow backwards through valves that are closed. Which means that the valves should therefore stop backflow. This argument fails when backflow happens when valves are open, i.e. when the sprinkler system is being used, the valves won’t prevent backflow.
When manual valves are closed, they should prevent backflow. However, if the valve leaks, or seals leak, you have a problem. That problem WILL happen sooner or later.
Electric solenoid valves are commonly used in irrigation systems. However, most automatic valves, like an electric solenoid valve, have a design flaw. So, they will not prevent backflow even while they are fully closed and “off”.
This is the result of the directional design of solenoid valves. These valves have a specific flow direction. However, if the flow goes the opposite way, the valve will frequently open slightly, thus allowing backflow to occur.
Selecting Backflow Preventers
As there are various backflow preventer types on the market, it’s good to understand the various options. Make sure the backflow preventer you want to use is legal in your area. That’s because location, regulations will vary. You can do that by checking with the municipality or the local water provider.
The questions below will assist you in deciding which type you need. The different types are described later in this article.
- Is the site a single family residence or commercial?
- Single Family Residence: Continue to question 2.
- Commercial, including all business properties, condominiums and apartment complexes. For commercial projects, the industry standard is a Reduced Pressure Zone (RPZ) Backflow Preventer (Reduced Pressure Backflow Preventer). This type gives the best protection. Commercial property owners are bound to be held to an extremely high standard if something goes wrong.
- Will you use pesticides, fertilizer, fertilizer added to the irrigation water, or use anything apart from pure water in the irrigation system? Including products labeled as safe, natural, and organic? Although these products may be safe when spread in the air, as they are concentrated in the irrigation system’s water, they will be more toxic.
- No: Continue to question 3.
- Yes: Use a Reduced Pressure Zone (RPZ) Backflow Preventer.
- Will the backflow preventers be installed in a valve enclosure below ground?
- No: Continue to question 4.
- Yes: The only type that may be installed in an enclosure under the ground is a Double Check Backflow Preventer .
- Can the backflow preventers be installed at a location at least 150mm (6”) higher than all sprinkler heads or drip emitters?
- Yes: Continue to question 5.
- No: Use a Double Check Backflow Preventer or a Reduced Pressure Zone (RPZ) Backflow Preventer.
- Is the space that will be irrigated relatively small, i.e. the back or front yard of a small home?
- Yes: Continue to question 6.
- No: Use a Double Check Backflow Preventer, an RPZ (Reduced Pressure Zone) Backflow Preventer, which is also called a Reduced Pressure Backflow Preventer. Or use a Pressure Vacuum Breaker .
- Can the valves be installed on pipes, more than 150mm (6”) above ground?
- No: Use a Double Check Backflow Preventer, RPZ (Reduced Pressure Zone) Backflow Preventer or a Pressure Vacuum Breaker.
- Yes: Use an Anti-Siphon Valve .
Still not sure what you need, or you want help installing it? Contact a local Plumber – Use the form below:
Types of Backflow Preventers
Control valves are used to switch a drip system or groups of sprinklers on and off. Irrigation systems will typically use a number of control valves, each used to turn on the sprinklers in different areas. Control valves may be manual or automatic.
Atmospheric Vacuum Breakers
Atmospheric Vacuum Breakers (AVB) are a type of sprinkler system backflow preventer that cost the least. Quite simply, it’s an air gap between the two plumbing systems. AVBs are installed on pipes directly after control valves.
When AVBs are installed for backflow prevention, one AVB must be installed after each of the control valves.
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They must be fitted at least 6 inches (150mm) above the highest drip emitter, bubbler, or sprinkler head outlet that is controlled by the specific control valve.
Local officials in some areas, and some AVB manufacturers, specify that AVBs be installed at least 12 inches (300mm) above sprinkler heads. They may never be installed in locations that may be underwater at some stage, such as underground boxes. AVBs are generally not economically viable if more than six valves are used. So, pressure vacuum breakers are a better option in this case. Also, some authorities don’t allow AVBs to be used.
Anti-siphon valves are mostly used rather than using a separate AVB and a valve. Anti-siphon valves are generally cheaper and easier to install.
Should any type of valve be installed on the pipes downstream from the AVB, the atmospheric vacuum breaker won’t work. That’s because the valve that is downstream will create back pressure. Which will cause the AVB’s vent to be pushed closed. The AVB won’t prevent backflow if the vent can’t open.
The only exception to this rule is a drain valve used for system winterization. Providing these are configured to only drain the pipes. A drain valve that is installed properly won’t create backpressure on the atmospheric vacuum breaker.
Anti-siphon valves are automatic or manual control valves that have an atmospheric vacuum breaker built in.
The same limitations that apply to AVBs are applicable to anti-siphon valves, i.e. height above sprinkler heads, no installation in underground boxes and no valves installed downstream except winterization drain valves.
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Anti-siphon valves are automatic or manual control valves that have an atmospheric vacuum breaker built in. The same limitations that apply to AVBs are applicable to anti-siphon valves, i.e. height above sprinkler heads, no installation in underground boxes and no valves installed downstream except winterization drain valves.
Because anti-siphon valves are simple devices, they are also low cost. Therefore, they are normally used in residential irrigation systems as a backflow preventer. Some authorities however don’t allow anti-siphon valves to be used.
Anti-siphon valves are generally installed in groups at the highest position of the area that will be irrigated. A main pipe is run from the water source to the locations of the anti-siphon valves. Pipes are then extended from the anti-siphon valves to the emitter tubes or sprinklers.
As water may periodically leak out of an anti-siphon valve, ensure they are installed where spilled water won’t cause problems. This water will leak out of the vent, located under the cover on top of the valve’s downstream side.
Water coming out of an anti-siphon is an indication of a problem that has to be resolved. It’s most often caused by something stuck under the anti-siphon seal jamming it open. Or the anti-siphon valve not having been installed above all the emitters or heads.
Pressure Vacuum Breakers
Pressure vacuum breakers (PVBs) are similar to atmospheric vacuum breakers. Except that only one needs to be installed in the main line going to the control valves.
They need to be positioned above ground. Also, it must be 150mm (6 inches) above the highest drip emitter or sprinkler head controlled by the valve.
Some local authorities specify that PVBs be located within 450mm (18”) of the water supply connection. In this case a PVB can’t be used unless the water supply is at the highest point of the area to be irrigated.
PVBs may also not be located in places where they may be underwater at any stage.
Some authorities don’t allow PVBs to be used at all. While others don’t allow them to be used with a drip irrigation system. When backflow occurs, PVB backflow preventers may spill or spit water out. So, they should therefore be installed in locations where this won’t cause problems.
RPZ (Reduced Pressure Zone) Backflow Preventer (Reduced Pressure Backflow Preventers)
Reduced Pressure Backflow Preventers are also known as Reduced Pressure Zone (RPZ) backflow preventers.
This is the gold standard of backflow preventers, used for high-hazard applications. This however also means that they are expensive.
Most commercial irrigation systems use a reduced pressure backflow preventer. They have to be installed 300mm (12”) above ground, although they don’t have to be above the sprinklers. They may also not be located in a place that may be underwater at any stage.
A drain must be located close to the backflow preventer if it is installed in a basement or structure. One valve should be installed upstream of all the other valves.
Double Check Backflow Preventers
In some cities, a double check backflow preventer is legal to use for an irrigation system. Also, local officials sometimes even recommended them. However, other cities don’t allow them for use in irrigation systems at all.
It should be noted that a Double Check Backflow Preventer and a Dual Check Backflow Preventer is NOT the same thing, although they may seem similar.
A dual check backflow preventer is used with liquids that aren’t toxic. Dual checks are typically used where a house’s water supply is connected to the city’s pipes. As the water used in homes is non-toxic, dual checks are acceptable. However, water in lawn irrigation systems is more likely to be toxic, so dual checks are not acceptable.
Double Check Backflow Preventers will always have two manually operated valves. One on the outlet and the other on the inlet. These valves are used to test if the backflow preventer’s operation is working properly. Plus, they are also used as an emergency shut-off. A Double Check also has a test cock to connect a test gauge. If it does not have test cocks and shut off valves, it isn’t a Double Check Backflow Preventer. Many authorities that permit double check backflow preventers to be used, don’t allow dual check backflow preventers.
Double check backflow preventers consist of two check valves that are spring-loaded in series. Plus, test cocks to enable the units to be tested properly. Also, there is a shut-off valve on each end.
Double check backflow preventers don’t use a vent that allows water to escape or air to enter the lines when there is backflow. It prevents backflow by relying totally on the seals of the 2 check valves to be tight.
In many areas where the use of a double check backflow preventer is permitted, they may be installed in a vault underground. You should however always check with local authorities to ensure that this is the case in your area.
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A double check backflow preventer may be installed below the irrigation system. So, they are often positioned in basements to prevent them from freezing. They must be easily accessible for testing and maintenance, irrespective of where they are installed.
Even where these preventers are legal to use, they’re not legal for irrigation systems where chemicals are added to the water.
Dual Check Devices
These are technically not backflow preventers. They are basically simplified versions of Double Check Backflow Preventers, without the test cocks or shut-off valves. This makes them flow control devices rather than backflow preventers.
They are typically used to prevent a water meter from running in reverse.
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Why Are Sprinkler Systems And Backflow Assemblies Winterized In Minnesota?
Winters in Minnesota tend to be extremely cold, resulting in lots of frozen water. Including water in sprinkler system pipes and backflow assemblies. When water freezes, it expands and will damage pipes and backflow systems. Contact a local plumber to prevent them from freezing. This will save you money by preventing expensive repairs.
Inspection of Backflow Devices
New Backflow laws have been adopted by the Minnesota Department of Labor and Industry, and other States as of January 23, 2016. Upon initial installation, all testable devices must now be tested annually.
“603.4.2 – The premise owner or responsible person shall have the backflow prevention assembly tested by a certified backflow assembly tester at the time of backflow preventer installation, repair, or relocation and not less than one annual schedule thereafter, or more often where required by the Authority Having Jurisdiction. Periodic testing shall be performed in accordance with the procedures referenced in Table 1401.1 (by a tester qualified in accordance with those standards).”Minnesota Department of Labor and Industry
Contact a local plumber to perform a backflow test. They will submit all the documentation to the governing agency or water purveyor on your behalf. If the assembly fails, they will provide a free estimate and discuss repairs with you before work starts. Repairs will be done by a licensed plumber.
There are consequences for not having your backflow devices tested – such as having the water shut off. So, use the form below to schedule your annual test or to have a backflow preventer installed or repaired.