What Can Cause a Backflow?

A lot of people are not aware about the importance of backflow testing and how it can prevent cross-contamination to occur in your water lines.

The water that flows into your home is usually kept at a standard pressure and should only flow in one direction. Like the movement of your water from your shower, to your toilet, and to your sink.

If there is an unexpected change in pressure on your pipes due to freezing, unusual high demand on the water supply, or bursting, there is a greater chance that a contaminated water from the ground or storage can enter your system.

Even when the water from the municipality is well-treated, an issue with water pressure can result into water contamination. Water pressure in the plumbing system can be impacted by something as basic as a leak in your pipes or in your neighbor’s pipes. It may also be altered by a water hydrant being drained or used or by a burst water main in the city.

When the water pressure in the system changes even a small amount, the flow of waste water away from the home could be altered. Rather than flowing away from the home, the waste water could flow into the fresh water supply. This can happen in a very short period of time, and your family could easily drink contaminated water without knowing it.

Backflow is a bad news. The unfortunate occurrence of contaminated water streaming back into your usable water supply can cause a painful, serious health condition or even death in you or your family members.

Many people believe that if they live in a developed area their municipality will provide a reliable source of clean drinking water for them. However, after you learn more about how the water supply and your home’s plumbing system works, you will see that the system is not fool proof and that a special plumbing service known as backflow testing is needed to keep your family safe.

A Preventative Device

Because this type of issue is recognized and rather common, many homes are equipped with a backflow preventer. This is a unique device that monitors changes in water pressure.
If it sense an adjustment in water pressure, a valve is triggered that prevents water from flowing backward into the home. This function occurs instantaneously, and you likely will not even be aware that the device was triggered. However, it can prevent illness and even death through its function.

Types of Backflow Preventers

Atmospheric Vacuum Breakers

The atmospheric vacuum breakers (AVB) are the simplest and least expensive types of backflow preventers. It contains an air inlet valve, check seat, and the air inlet port.

Atmospheric vacuum breakers (AVB) must be installed on the pipe directly after every control valve. The water flowing through the AVB causes the air inlet valve to close against the air inlet port. When the normal flow of water stopped, the air inlet valve will fall to form a block for the backsiphonage. Keep in mind that AVB’s protects against non-health hazards or health’s hazards under backsiphonage only and is not design to protect against back-pressure.

Pressure Vacuum Breaker Assembly (PVB)

Pressure Vacuum Breaker Assembly (PVB) is an assembly that contains an internally loaded check valve and an internally loaded air inlet valve located on the discharge side of the check valve.

Each valves acts independently with the air inlet valve that is located in the downstream of the check valve. Test cocks and shut-off valves can be seen at each end of the assembly and unlike the atmospheric vacuum breaker, the Flow Water Out PVB can be tested. Lastly, the pressure vacuum breaker is not designed to protect against backpressure.

Base on the design and operation of Pressure Vacuum Breaker Assembly (PVB), the following criteria must be observed:

  1. It must be installed with atleast a minimum clearance of twelve inches above the highest downstream point on the system.
  2. Shut-off valves may be installed on the downstream of the PVB.
  3. MUST not be installed if back-pressure is a potential threat.
  4. MUST be installed vertically with the inlet at the bottom.

Double Check Valves

A double check valve (DCV) or also called as double check assemblies (DCA), is the most common choice for underground or in-line usage. It consists of an inlet shutoff valve, two independently operating spring-loaded check valves (usually inside a single valve body), four test cocks, and an outlet shutoff valve.

Double check valve (DCV) can be installed either horizontally or vertically- an in-line installation means that the valve will be installed parallel to the piping, whichever way the piping runs. Unlike with a PVB installation, a DCVA does not need to be installed at least a foot above the highest downstream point in the plumbing system. However, it does require a foot of clearance underneath for maintenance purposes.

Spill-Resistant Vacuum Breaker Assembly (SVB)

Unlike PVBs who may sometimes leak water, Spill-resistant vacuum breakers (SVBs) can solve all the problems of leaky assemblies. SVBs have similar construction with PVBs but it does have an additional diaphragm seals that keeps water from spilling out of the air inlet when the assembly becomes pressurized.

Spill-resistant vacuum breakers (SVBs) are design to protect against a non-health hazard like pollutants or a health hazard just like contaminants but under a backsiphonage condition only.

Air-Gap Separation

Air-gap separation (AG) is the most common method in preventing cross-connections that results in backflow do to either backpressure or backsiphonage. In many homes in the US, it is still the only method that is approved for preventing this type of backflow.

A physical separation between the free-flowing discharge end of a potable water supply pipeline and an open or non-pressure receiving vessel. Must not be used in an area with a dangerous atmosphere.

Air-gap separation (AG) should be atleast twice the diameter of the supply pipe measured vertically above the overflow rim of the receiving vessel; in no case less than 1 inch (2.54 cm).

Double Check Valve Assemblies

Double Check Valve Assemblies are installed above ground or inline and must not be used with chemigation. It can be installed either horizontally or vertically and can be installed where the potential for backsiphonage or backpressure is present.

Do You Need Your System Tested?

The truth is, every facility and home needs to have a backflow preventer installed in their water system. You’re probably wondering how you would know if your water is safe for drinking. That’s why backflow testing is really important for any homeowner.

However, even if you have a backflow device installed in your home, it needs to be tested periodically. Because it functions in a manner that is not evident to homeowners, it can be impossible for a homeowner to determine if it is working properly until illness from contaminated water occurs. The best way to prevent this from happening is to schedule annual testing through a plumber. The plumber can inspect the device and can make repairs or a replacement if needed. And sometimes, there is a possibility that your backflow preventer device could fail to do its job.

Here are some signs that you need to get your system tested:

  • Foul-smelling water
  • Foul-tasting water or water with a minerally, metallic, or chemical taste
  • Cloudy water
  • Visible sedimentation in water

Backflow testing may be a task that is easy for homeowners to overlook, but it is nonetheless highly important to complete. Contact a plumber to schedule an appointment for testing if service is needed in your home.

Want more information on back-flow testing in the San Mateo area? Just call James Caccia Plumbing at (650) 442-1470, and take the proper precautions.