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(707) 539-4533 |  Sonoma Napa and Marin Counties

updated February 2023

Before installing a new HVAC system, a technician will usually perform something called a backflow test. Backflow is generally more of a plumbing concern, but it’s also HVAC adjacent since the pipes required for some furnaces, air conditioners, and other HVAC devices are also at risk for backflow. A test is a good way to make sure that nothing from your HVAC pipes is going to contaminate the rest of your plumbing, and vice-versa. Here’s a little information on how backflow tests work, why they’re so important, and how you can perform one yourself if you like.


HVAC 101 Everything you need to know


What is a Backflow Test and How Does It Work?

Typically, every pipe in your plumbing system flows in only one direction. Clean water flows into your plumbing from the water main, comes out through your sink, shower, or any other appliance, and then goes down the drain once it’s been used so it can flow back out. However, sometimes certain pressure imbalances or suction can cause the water to start flowing backward. When backflow occurs, dirty water from your shower drain, dishwasher, or even sewage water can find its way into your supply of clean drinking water. Not only is this extremely unpleasant, but it can also lead to water damage in your home or illness if you unknowingly drink the backflow water.


In order to avoid this problem, modern homes are outfitted with devices called backflow preventers. As you can probably guess from the name, backflow preventers are designed to stop backflow before it reaches the rest of your water supply. This happens through special valves, vacuum suction, and sometimes air gaps. If your backflow preventer is working properly, you might not ever even know it was there. However, if the preventer fails, you could find yourself with sewage water coming out of your kitchen sink, and nobody wants that.


With all that in mind, you might still be wondering “What is a backflow test?” When a plumber or HVAC technician performs a backflow test, they’re checking each of the backflow preventers in your house to make sure they’re all working properly. There’s typically a backflow preventer installed in the cross-connections between your main water supply and each appliance that pulls from it. Backflow testing involves going to those connections and making sure every preventer is working the way it should. Even a single broken backflow preventer can contaminate your clean water plumbing, so it’s important to be thorough.


In addition to the backflow testing, a technician or plumber might also conduct a water pressure test. Pressure imbalances are the cause of almost all backflow issues, so it’s important to check the pressure throughout your house to make sure there are no trouble spots. A sudden drop in water pressure can cause dirty water to be sucked back into the clean water supply – this is called back-siphonage, and it’s the most common cause of backflow. It’s essentially the same as sucking water through a straw; the lowered air pressure in your mouth causes water to rise through the straw due to atmospheric pressure. On the other side of things, if the water pressure is too high in any part of your plumbing, it can cause something called back-pressure. This is like blowing through a straw and pushing the water back into the glass; the higher pressure in your mouth forces the air and water out the other end of the straw. Either of these pressure imbalances will cause backflow to enter your clean water supply, so regular water pressure tests are a good way to stay ahead of any potential issues.


What are the Advantages of a Backflow Test?

The most main benefits of backflow testing should be pretty apparent. Nobody wants wastewater in their drinking supply, and making sure the backflow prevention systems are functioning properly is the best way to keep that from happening. Backflow can also cause serious damage to your plumbing or the areas surrounding your fixtures if flooding also occurs. If you’re wondering how to prevent backflow, regular maintenance is the best practice for avoiding any number of potential issues down the road. It’s a lot better to shell out about $80 once a year instead of potentially thousands of dollars to fix your plumbing after backflow has occurred.


Backflow can also cause serious illnesses in you or your family if you drink the tainted water inadvertently. The main culprit for backflow-related illness is sewage water. Besides the obvious reasons why nobody should want to drink water contaminated by sewage, human waste also contains a pretty wide variety of bacteria, viruses, and parasites that can wreak havoc on your body. Many diseases like typhoid fever, dysentery, and giardia have nearly disappeared from everyday American life because of modern-day water treatment and hygiene techniques, but backflow can hit you with any of these blasts from the past.


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The most common single cause of backflow is your everyday garden hose, and this kind of contamination can come with adverse health effects as well. When water from your lawn or garden backs up through the hose into your clean supply, it brings everything that was in the dirt with it. This can include parasites and bacteria as well as any fertilizer or pesticide that you use on your lawn. Ingesting water that’s been tainted with fertilizer can lead to nitrate poisoning, which requires immediate medical attention and can cause hospitalization and long-term health effects. Other potential sources of waterborne illness include standing water from sprinkler systems or boilers and industrial chemicals if you’re in a commercial building.


If your backflow preventers fail, the effects might not be limited to just your home. If backflow is allowed to reach and contaminate the water main, you could end up with a full-blown public health crisis in your neighborhood. For this reason, regular backflow testing is legally required by many states, including California. A failure to stay up to date on backflow testing could result in some fines or penalties, especially if you’re running a business. Luckily, all these consequences can be avoided if you stay on top of your maintenance schedule and give your plumber or HVAC technician a call every year. The testing is relatively inexpensive, and you can include it as part of your regular HVAC maintenance.


How to Perform and Interpret Results from a Backflow Test

While the simplest option is to just have a professional take care of your backflow testing, hardcore do-it-yourselfers might prefer to handle the testing themselves. In order to test your own backflow preventers, all you need is a backflow testing kit and some rudimentary plumbing skills. The cost of a testing kit can range from about $200 all the way up to $2000, so be prepared to spend if you want to test everything yourself.


Step 1 – Shut off Water

First things first, you should shut off the water supply in your house. Make sure to warn everyone in your household before you start the testing process since they won’t be able to use the water until you’re finished.


Step 2 – Check Device

There are several different types of backflow preventers, and each one has its own unique testing process. Any manual you find will list the different procedures for each type of preventer, so all you have to do is identify which kind you have. You can find this out by checking the documentation provided by the manufacturer when you purchased the preventer.


Step 3 – Gather Test-Cocks

A test-cock, often colloquially referred to as a “thingy,” is a small valve that you can attach to another valve for testing purposes. The test-cock draws a little water from the full valve so you can test the pressure without having to take the whole system apart. You will generally need at least two test-cocks for backflow testing, but the exact number will depend on the type of preventer you have. You should make sure to label each test-cock with a number so you can keep track of which is which.


Step 4 – Close Downstream Valve

Any backflow preventer should have two different shut-off valves: one upstream (closer to the source of the water) and one downstream (closer to the water’s destination). In order to test the preventer, you’ll have to shut the downstream valve while leaving the upstream one open. This allows the preventer to fill with water but blocks any flow further than that. Don’t forget to open the valve again when you’re finished!


Step 5 – Attach Hoses and Test

The specifics of this step can vary pretty wildly depending on the type of preventer you’re testing. There are about 10 different procedures, one for each type, so you’ll have to find the directions for yours in the documentation that came with the testing kit. The directions will also explain how to read the results from the backflow test, which involves checking a few different gauges for pressure readings.


Once you’ve finished these steps and noted all the readings, don’t forget to replace everything and open the downstream valve again. While the procedures involved in testing backflow preventers might seem complicated when you first give them a try, there’s no reason why you shouldn’t be able to take care of them yourself. That said, having them handled professionally is relatively inexpensive, so that’s an excellent choice as well.


What Does it Mean if There’s No Water Flow? – If there’s no water at all flowing into the preventer, double-check to make sure you closed off the right shut-off valve. If the upstream valve is open and you’re still not getting any water flowing from the source, then there could be a problem with the preventer or even the water main itself, and you should get in touch with a plumber to take a look.


Why You Should Perform Regularly Scheduled Water Pressure Tests

Aside from the regular backflow testing, it’s always a good idea to check the water pressure fairly regularly as well. This is a lot easier to do and only requires you to attach a gauge to a water fixture in your house. Home water pressure is usually handled by a single regulator somewhere in your home, so you should only need to test a single fixture. If you get your water from a municipal source like a water main, test the pressure at an outdoor spigot close to the road. If you use a well, use a faucet or fixture that’s close to the pressure tank attached to the well.


Because imbalances in water pressure are what cause backflow, catching any potential high or low-pressure spots in your plumbing before they become serious problems is ideal. If you’d prefer not to handle this on your own, you can always get your regular plumber to check the water pressure when they test the backflow prevention. We recommend checking the water pressure about once a year or more, depending on the specifics of your situation.


Modern plumbing works through pressure almost exclusively. This is an extremely efficient way of moving water from one place to another, but it also means any sudden drop or spike in pressure can wreak havoc on the system. Besides causing backflow, pressure issues can also lead to burst pipes and leaks as well as rendering fixtures ineffective. If you notice a change in the water pressure of any of your fixtures, like the shower or the sink, you should have the pipes checked by a professional. You could be at risk of backflow, pipe damages, flooding, or other costly plumbing emergencies.


Backflow Testing in Santa Rosa

If you live in a house rather than an apartment, you’ve almost definitely had at least one backflow test performed by a plumber or HVAC technician. California law requires that all backflow preventers be tested at least once a year for public health reasons, so unless you just moved to Santa Rosa in the past few months, you’ve certainly had this procedure performed in your home. However, since these tests are often parceled with other HVAC or plumbing maintenance work, you might not be entirely sure how they work, or even what a backflow test is.


A backflow test is just one of the myriad of small things that all homeowners need to keep up with to prevent potential catastrophes in their houses. For that reason, we’ve put together this blog post that covers some of the basics of backflow testing so you can be aware of what’s going on, even if you decide to let the professionals keep handling it for you. This post will cover the definition of backflow, how the testing works, and why it’s so important to stick to the testing schedule. These tests might be only a small part of every homeowner’s long to-do list, but ignoring them and letting your backflow preventers fail will only set you up for potential fines, illnesses, and some particularly unpleasant property damage down the line.


What is Backflow and How Do You Prevent It?

The indoor plumbing system in your home probably isn’t something that you put all that much thought into unless something is going wrong. Most of us tend to take running water for granted, but it’s actually something of an engineering marvel. Modern-day plumbing can draw fresh water from a water main, force it out through faucets and other fixtures at an impressive speed, and finally drain any dirty or extra water back out so it doesn’t just pool somewhere underneath your home. Trying to manually move that much water with machinery would be an absolute disaster for anyone’s power bill, so all of this flowing back and forth is done through very careful control of pressure and suction. That way, the water moves through the pipes without any need for external force or energy expenditure.


In order for these plumbing systems to work properly, all the water needs to be flowing in a single direction through each pipe. Instead of going back and forth through the same pipes, water flows in a kind of cycle. It starts out in the municipal water main underneath your street, then flows through one set of pipes into your house. Water exits those pipes through your faucets, shower heads, gardening hoses, or anything else in your home that has running water. Then, any excess or dirty water flows down through your drains into a new set of pipes that transfer it into the sewers or anywhere else wastewater is diverted. Maintaining this single-directional flow is extremely important.


Backflow occurs when the flow of water through your pipes is reversed for one reason or another. This can cause your fresh water to get stuck back by the water main so it can’t come out through your faucets, which is inconvenient enough. However, much more concerningly, backflow also causes wastewater to flow backward and come back out through your drains or toilets. That means dirty water from your dishwasher, soapy water from your shower, and even raw sewage from the toilet can suddenly come flowing back out in the wrong direction.


So how do you avoid this costly and often disgusting problem? The answer is that all modern homes are outfitted with special devices called backflow preventers. There are several different kinds of preventers that work in different ways, including special valves and vacuums installed within your plumbing system. Air gaps are another common form of backflow prevention. Have you ever wondered why the faucets in your house never go low enough to dip under the waterline when your sink is full? That gap between the water in your sink and the end of the faucet is there on purpose to prevent backflow. If the faucet dipped under the waterline, it would be easy for the pressure inside the pipes to be reversed, causing the fixture to start sucking that water up into the pipes and drawing wastewater out from the drain. Even the faucet in your tub, if you have one, is placed above the overflow drain hole for this very reason. Backflow preventers are important pieces of safety equipment for any home and are generally mandated by the state.


How Backflow Testing is Performed in Santa Rosa

Every home features several backflow preventers, typically one at every cross-connection in your plumbing system. In plumbing lingo, a cross-connection is any point where two sources of water pass by each other, potentially connecting and mixing together. There’s a cross-connection for every fixture in your house, where the pipes leading to the fixture connect to the main water line running through your home. Since every appliance that draws water generally has its own backflow preventer, they add up pretty quickly. There’s also a preventer at the intersection between the main water line to your house and the city water main that connects directly to the reservoir. In Santa Rosa, those water mains mostly connect to the Russian River and are managed by the city itself. However, while the city takes care of the water main, each homeowner is responsible for managing the important backflow preventers on their own property. If those preventers fail, wastewater can end up flowing back into the public water main, so there are some pretty strict fees involved if you fail to maintain and test the preventers.


Backflow testing is generally performed by either a plumber or an HVAC technician. While the connection between backflow testing and plumbing is fairly obvious, some people are surprised to hear that many HVAC companies also handle these tests. However, since so many HVAC units need to be connected to boilers, hot water heaters, and other hydronic systems, it’s not uncommon for technicians to receive training so they can just handle the backflow testing themselves, preventing the homeowner from having to call in a plumber after their new furnace or air conditioner is installed.


The testing process itself varies pretty wildly depending on the type of preventer you have installed in the pipes. The plumber or HVAC technician will generally just go through each preventer one at a time, testing each one individually. In order to pass backflow testing, every preventer in your house needs to be working correctly, and any broken ones should be replaced immediately. Even a single broken backflow preventer can cause damage to your home or even make you and your family sick, so it’s important to make sure every single one is working at full capacity.


While it’s not usually mandated, a plumber or technician might also perform some pressure testing on your pipes while they’re testing the backflow preventers. The most common cause of backflow is a sudden drop in pressure in your pipes, causing water to rush backward to fill the vacuum – this is called back-siphonage. It’s essentially the same way a straw works. When you suck water through the straw, what you’re actually doing is lowering the pressure inside your mouth. That causes the water to flow upwards through the straw due to atmospheric pressure. Back-siphonage is most commonly caused by garden hoses that have been left in a pool or puddle of standing water. If the pressure inside the hose suddenly drops, it’ll start sucking the water back up instead of forcing it out.


A sudden increase in pressure can also cause backflow from the other direction. If lowered pressure is like sucking water up through a straw, increased pressure is like blowing through the straw and forcing the water back into the glass – along with saliva and anything else that was in your mouth. In this particular metaphor, the backwash from your mouth could be any wastewater that was in the pipes: sudsy water from the shower, raw sewage from the toilet, and so on. Making sure the pressure in your plumbing system stays consistent is the best way to avoid any backflow, so it’s a good idea to have it checked often.


Why is Backflow Testing Important?

Besides the fact that annual backflow testing is mandatory in California, preventing backflow is also something well worth doing on its own merits. First things first: backflow is unsanitary, unpleasant, and overall just disgusting. Nobody wants to see their drinking water contaminated with wastewater of any kind unless they just so happen to enjoy the taste of suds and rotten food. Making sure that your backflow preventers are in good working order is the best way to avoid any contamination in your water supply, and the benefits of clean water should be pretty self-evident.


Besides the problem of contamination, backflow can also wind up being extremely expensive for you. When water starts flowing backward through your pipes, it doesn’t just travel neatly back to the water main. It overflows your sink, your tub, or, worst of all, your toilet, causing wastewater to leak all over the floor and leaving you with a repulsive mess and some costly water damage if you’re unlucky. If backflow is able to back up in your pipes, it can also cause them to burst, creating more flooding issues in your home and forcing you to shell out for repairs. In California, a burst pipe in your sewer line can cost up to $3,000 or $4,000 – a hefty price. Backflow testing, on the other hand, will only cost you about $80 a year, which means that a single instance of backflow can easily cost as much as 50+ years of regular annual testing.


The most serious consequences of backflow, however, can end up being to your health. The main culprit of backflow-related health issues is always raw sewage water. Human waste is a breeding ground for all kinds of nasty things, including viruses, bacteria, and parasites. One of the main reasons why modern-day plumbing is so important is that it allows us to avoid hundreds of diseases that used to wreak havoc on human populations in centuries past, including dysentery, typhoid fever, Legionnaire’s disease, and giardia. All of these diseases are most commonly caused when human waste is allowed to contaminate the area’s drinking water, which is why they were most commonly seen in America during the colonial and pioneer eras. Today, very few people suffer from them in the developed world, but backflow can easily cause an outbreak in your household if the contamination is subtle enough to go unnoticed for a time.


As we mentioned earlier in this post, the most common cause of backflow these days is a garden hose that’s been left in a pool or puddle of standing water. If the end of the hose is in the water, there’s no air gap to prevent backflow from occurring. When that does happen, it can cause plenty of other health issues. If water from your lawn backs up into your house through the hose, it brings everything in the dirt with it, including diseases, parasites, and any pesticides or fertilizers you use on your lawn. Pesticides can be harmful if ingested, and drinking any water that’s been tainted by fertilizer can leave you with nitrate poisoning, which often leads to hospitalization and long-term health effects.


Finally, the effects of backflow aren’t necessarily just contained to a single household. Diseases like typhoid and dysentery can easily be spread within the population, causing a public health crisis. In a worst-case scenario, backflow can actually make its way into the public water main, causing the contaminated water to spread through your neighborhood. These consequences to the public are exactly why states like California take backflow testing laws so seriously. If you allow a year or two to pass without doing any backflow testing, you could end up with a hefty fine or could even be cut off from the municipal water main, so it’s really not worth messing around with.

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Avoiding Backflow on Your Own

In Santa Rosa, like the rest of California, the regulations state that backflow testing can only be performed by someone with the proper license and training. That means that, unfortunately, you can’t handle your own backflow testing even if you learn how. The risk of making a mistake is just too high, especially since failing to notice a broken or otherwise nonfunctional preventer can lead to contamination in the water supply of your entire neighborhood. However, there are plenty of things you can look out for to lower the risk of backflow throughout the year. Here are a few of the situations and fixtures that come with a higher backflow risk and how you can lower that risk.


As previously mentioned, most modern fixtures come with their own built-in backflow prevention in the form of an air gap. Sinks, showers, bathtubs, and toilets all feature gaps between any spouts or faucets connected to the incoming water line and any standing or draining water flowing to the outgoing water line. In cases where backed-up standing water can reach the spouts, like in toilet bowls, the fixture is always installed with a mechanism that automatically blocks off the spout when the drain is stopped. That means backed-up water can never reach the clean water source and cause backflow – good news for you. However, there are some water sources that don’t feature air gaps and are more vulnerable to backflow.


We’ve mentioned garden hoses a few times in this post, but it’s worth stating again that they’re the single most common culprit of backflow in residential areas. When we fill up a pool or other large container with water, we commonly leave the end of the hose inside the container itself so it doesn’t slide out and spray water all over the ground. However, when the end of the hose is submerged, even the smallest drop in pressure can cause the flow of water to be reversed, causing the hose to create suction instead of expelling water. The universality of hose connections also makes them more vulnerable to backflow. Unfortunately, outdoor hose spigots are rarely outfitted with backflow preventers, so there’s nothing to stop the water from flowing straight back into the pipes. Luckily, you can pick up a vacuum breaker for under $10 that screws onto the end of the spigot and prevents any backflow by acting as a one-way valve. If the pressure inside the valve drops at all, it closes entirely and prevents backflow. We highly recommend picking up breakers for every outdoor spigot in your home.


Handheld shower heads and sink spray heads also come with a higher risk of backflow. Like garden hoses, these detachable heads can be submerged in water, eliminating the air gap and leaving them vulnerable to backflow. Luckily, all these fixtures are required to be fitted with their own individual backflow preventers, making them safer to use even submerged in water. However, putting them in standing water does increase the chances of backflow even with the preventers installed, so we’d recommend being careful when you use them. After all, it’s always better to be safe than sorry, especially since the built-in preventers in the detachable heads can’t generally be tested easily, so you have to take it on faith that they’re still working properly.


Automatic irrigation systems like sprinkler heads are also at higher risk since they’re frequently submerged in water from the lawn. Backflow from sprinklers is particularly dangerous due to pesticides, fertilizers, and any other chemicals used to protect your lawn from the elements. When you pick up an automatic sprinkler system, make sure that the system has been outfitted with enough backflow preventers, and make sure they’re checked every year. Not every irrigation system comes with preventers, so you’ll have to have them installed if they’re not already there.


Some HVAC appliances, typically furnaces, work by using water to transfer heat throughout the system. Hydronic heating systems are typically hooked up to a central boiler that draws from the main water line in your house. The water in these systems is usually pretty stagnant and filled with minerals leached from the pipes, so you don’t want it leaking into your drinking water. The best way to avoid backflow from the boiler is to add a dual check valve to the connection with the main water line. Any HVAC technician should be doing this automatically when they install the system, but it never hurts to make sure. The valve will need to be replaced every five years or so – the HVAC contracting company that installed the boiler will generally keep a record so you know when to swap out the valve. Installing boilers is why many HVAC contractors receive training and licensing in backflow testing and are more than capable of performing your regular annual testing.


Where to Get Backflow Testing in Santa Rosa

You can get the backflow preventers in your home tested by contacting either a plumber or an HVAC contractor with a backflow testing license. The testing is important but not especially difficult, so you may as well work with whichever option quotes you the best price for the work. If you feel that you have a plumber or HVAC contractor who is particularly trustworthy, it’s never a bad idea to give them the extra work instead of hiring someone unfamiliar.


If you live in Napa, Sonoma, or Marin counties and you’re looking for someone to handle your backflow testing, Valley Comfort Heating & Air is more than happy to help. We’re primarily an HVAC company, but we have more than enough experience with backflow testing to take care of yours safely and accurately. You can get in touch with us today through our website here, in our storefront location in Santa Rosa, or by giving us a call at (707) 539-4533.