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BACKFLOW TESTING

What Is Backflow?

Backflow is a type of plumbing problem that occurs when your wastewater does not flow in the right direction. Instead of flowing down into your sewer system, the wastewater instead travels into your fresh water supply. There is a variety of different situations that can count as backflow. In some cases, backflow can cause dramatic gushes of discolored water from your faucets. In other situations, backflow can be so subtle that your water supply’s color, smell, or taste might not change noticeably.

There are several different ways that backflow can happen. It is usually divided into back-siphonage backflow and back-pressure backflow. Back siphonage occurs when a vacuum inside of your pipes physically sucks wastewater backward. Meanwhile, back pressure happens when excessive wastewater pressure causes wastewater to flow in the opposite direction.

Both types of backflow have the same basic result. You end up with wastewater from your toilets and drains coming out of your faucets. The contaminated water supply can cause a huge, disgusting mess throughout your home. Even smaller levels of backflow are still problematic. You might not notice a difference, but you can still get sick from the toxic chemicals and dangerous microbes in wastewater. Backflow is also dangerous for your pipes. When your plumbing system has backflow, your pipes are more likely to corrode, warp, or develop leaks.

How to Tell if You Have Backflow

Since backflow can happen so gradually, you might not realize you’re dealing with this plumbing issue. Backflow can usually only be confirmed by testing your water quality.

Here are a few signs that it might be time to test your home for backflow.

Strange odors around your faucet
Slow moving drains
Water that is brown, yellow, pink, or otherwise discolored
Strong sulfur smells from your water
Odd tastes in your water
Small particles floating around in your water

Causes of Back-Pressure Backflow

The water pipes throughout your home are all part of a carefully balanced system. A combination of pipe size and pipe placement is supposed to ensure that upstream water supply pressure is always higher than downstream water removal pressure. Water flows in the direction of least resistance, so this allows the clean water to “push” wastewater away from any water supply pipes. However, some plumbing mixups can cause pressure in water removal pipes to become higher than the water supply pressure. When this happens, the wastewater flows back upstream, causing a back pressure backflow to develop.

Back-pressure backflow often happens when your plumbing system was installed incorrectly. There are a lot of little mistakes that can add up to cause water pressure differentials. This is especially true if your plumbing system includes pressure-producing fixtures like elevated water tanks, boilers, or water heating systems. These can dump a lot of water into your drains at once, resulting in backflow. Even small things like the heat expansion from a boiler can increase pressure in the wrong part of your pipes. These disruptions may change water pressure levels enough to cause back pressure backflow to happen.

Back pressure backflow is also sometimes caused by a plumbing problem. If you have a leaky pipe, water supply pressure can drop just enough to let other plumbing issues make your wastewater pressure higher than your water supply pressure. Problems with your wastewater removal lines may also increase downstream pressure. If you have a clog in a drain line, water can back up behind the clog, increasing pressure enough to result in backflow.

Causes of Back-Siphonage Backflow

Back-siphonage backflow is also linked to uneven water pressure levels, but it’s more drastic. Instead of water just accidentally flowing in the wrong direction, back-siphonage happens when a vacuum occurs. The negative pressure can pull wastewater up into your supply lines very suddenly and sharply. Back siphonage is less common than back pressure, but it can result in more clearly contaminated water.

Back siphonage tends to happen when a lot of water is suddenly removed from your water supply system. It is most commonly associated with firefighting efforts. When firefighters are using a hydrant, the extreme drop in water pressure can end up forcing wastewater up into your water supply. Back siphonage can also occur when a water main break lets all your potable water spray out of your system. This tends to create a vacuum in water supply pipes that lets back-siphonage develop.

How to Prevent Backflow From Affecting Your Home

As you can see, there are multiple ways for backflow to occur inside your home. Some of these causes are preventable. Keeping your plumbing system up to code is one of the best things you can do. Local building laws regulate pipe sizes, placements, and angles to help minimize the risk of backflow.

You also need to remember that your entire plumbing system is designed to work together. Doing something like adding a new boiler can disrupt water pressure levels everywhere. To prevent these sorts of plumbing mistakes, you should consult with professionals any time you want to change part of your plumbing system or install a new fixture. They can help you figure out if your wastewater and water supply lines are up to the task.

Even if your plumbing system was perfectly designed, outside forces can still cause backflow to happen. To protect your home, it is a good idea to try some backflow prevention measures. There are a variety of plumbing add-ons that force water to flow in a single direction. These are very useful for halting backflow in case of a water line break or another issue. To protect a single faucet, you can install a hose bib backflow preventer. This compact, affordable device uses a spring-controlled seal to keep water from flowing backward. Another similar option is a pressure-type vacuum breaker. This device continuously monitors water pressure for a specific part of your system and closes a valve if it detects an imminent backflow.

Other backflow prevention measures can be installed within your plumbing system to provide more widespread protection. Barometric loops and air gaps are two styles of pipe placement that help regulate water flow and prevent siphoning. You can also use options like a reduced pressure principle backflow preventer. These more complex systems use multiple valves to control water pressure, and they can protect your whole home from any backflows.

RPZ TESTING

What Is A Reduced Pressure Zone (RPZ) Valve?

Reduced pressure zone assemblies, also commonly referred to as reduced pressure zone (RPZ) valves or RPZ backflow preventers, are an essential system that prevents the backflow of clean water to avoid contamination.

RPZ backflow preventers are designed to prevent contaminated water from mixing into clean municipal water supplies and are commonly used by municipalities, homes, and commercial buildings. These valves provide reliable protection against back pressure and siphonage, safeguarding water supplies from any form of contamination.

RPZ valves are pivotal in preventing toxic chemicals, hard metals, pesticides, and other harmful compounds from contaminating water supplies. In residential buildings, a RPZ device is used with sprinkler irrigation systems, boiler systems, fire suppression systems, and forced-air furnaces where it acts as a safety mechanism.

How Do RPZ Valves Work?

Image via Unsplash by kevin_butz

In a typical RPZ assembly, two one-way valves are connected to prevent water from returning to the supply line. This system works by ensuring that the incoming fluid has a higher pressure than the water entering the downstream supply. To prevent minor backflow leakage, the closure of one valve creates a pressure differential, thus tightening the valves and effectively sealing the system from backflow.

For a municipal water system, if at any time the pressure at homes exceeds the pressure on the supply side, the two RPZ valves close preventing backflow. If either of the check valves leaks, the relief valve is designed to open and discharge water to the outside, ensuring that water never returns to the supply line.

Because of their design, RPZ backflow preventers experience more high volume and pressure loss than double-check systems. Plumbers must account for these losses when designing drainage systems. Fluctuations of pressure, either downstream or upstream, will prompt the RPZ assembly to discharge small amounts of water periodically.

RPZ backflow preventers must be set up in areas with adequate drainage because a large volume of water will flow from the relief valve. For this reason, RPZ assemblies shouldn’t be installed in areas where the discharge water can cause damage — adequate drainage must be considered in areas fitted with RPZ valves.

How Do RPZ Devices Prevent Contamination?

Rapid and unexpected reduction of pressure in pipelines can present an extreme risk of contamination to water supplies. When water pressure goes down, water flows in the wrong direction, bringing contaminated water from home appliances and other industrial processes with it. Even the slightest fluctuation in pressure can cause backflows and contaminations.

Also, use of pesticides or fertilizers in your backyard together with your home’s fire suppression system poses a danger. The standing water in your water supply system can get trapped and lead to bacterial and mineral growth, which can contaminate your clean water supplies.

When there is a water leak in your supply lines, hydrant flushing, city water main break, or use of hydrant to fight fire, pressure in the water system drops. When this occurs, a RPZ prevents backflows, effectively preventing clean water from backing up to supply systems hosting potential contaminants.

Installing RPZ Backflow Preventers

When installing RPZ valves, contractors should avoid installing them in areas prone to flooding, places above electrical equipment, and positions that expose the valves to mechanical damage. The area should also be in a heated enclosure to prevent freezing, which can lead to ice buildup inside the valves, which can block water from flowing.

Because of fluctuating pressures, designs should factor in the intensity and frequency of the fluctuations. For instance, installation of a single-check valve upstream of the RPZ valve prevents fluctuation of pressures upstream, which are usually the primary cause of frequent discharges through the relief valve.

Unless the valve is specifically approved for vertical installations, RPZ valves should be installed horizontally with the relief valve mechanism discharging downward. In order to prevent any fouling of the RPZ assembly elements, plumbing engineers should install in-line strainers upstream of the RPZ valve. The valves must be installed above the floor surface to facilitate easy and fast inspection, testing, and maintenance.

RPZ Valve Testing

After the installation process, the reduced pressure zone device installed on plumbing systems requires regular tests by certified plumbers. Illinois water protection codes state that RPZ valves must be tested at least once every year. These tests are essential as they ensure that the valves are operating efficiently to protect the city water supply and drinking water from contaminants.

Only a certified assembly tester should perform the RPZ backflow preventer test, using a properly calibrated tool. Testing procedures may vary from state to state, but it must comply with the Department of Health and Illinois Plumbing Codes. Building maintenance workers, contractors, and plumbers use RPZ testers to measure the pressure difference between two points.

Before beginning the test process, contractors must:

Get permission to shut down the water supply and notify the users of the impending interruption.
Determine the direction of flow (crucial in differentiating downstream and upstream).
Identify the test cocks.
Install testers.
Perform repairs if necessary.
Write a report.

The three-valve RPZ and the five-valve RPZ are the common RPZ testers approved for testing backflow systems. Since the five-valve RPZ tester allows testing procedures to take place without disconnecting any hoses, it is the most popular tester.

RPZ Calibration Tests

RPZ calibration tests should be done annually by accredited contractors and plumbers. While most companies only undertake calibration tests on the gauge on an RPZ tester, it is a good idea to test the system for leaks, inspect wear and tear of the valves, and account for pressure differences if any. Testing the entire RPZ assembly allows early detection of malfunction within the parts of the RPZ unit.

The Department of Health made it mandatory that all water systems that provide water for nonpotable use should use backflow preventer systems such as the RPZ. This means that public water supplies, commercial property owners, and residential property owners should install backflow systems to protect users from health hazards that can result from water contamination.