What Is an Anti-Siphon Valve and How Does It Work?

Having clean drinking water is of vital importance. A tool that does the lion’s share of the work in ensuring you and your family have access to this basic need is the anti-siphon valve. If you’ve never heard of it, you might naturally be asking, “What is an anti-siphon valve?” and wondering how it works. Our guide covers the basics of what they are, how they work, how much they cost, and tips for troubleshooting should you notice a problem with yours.

What Are Anti-Siphon Valves?

An anti-siphon valve comes in two forms: a valve and a faucet. You’ll often find these on sinks, hose connectors, and outdoor plumbing features. These valves are responsible for preventing the backflow of dirty water from entering your home, where it could mix with your drinking water. These are essential parts of your home, as housing codes require them for all outdoor faucet types, and plumbers use them for all hose bib types. 

How Do Anti-Siphon Valves Work?

What’s unique about these valves is that they only allow water to flow in one direction. To demonstrate, say you install a sprinkler system and you use a fertilizer injection system for your lawn. In this instance, the last thing you want is the water you’re mixing with fertilizer to siphon into your water supply line.

This is where anti-siphon valves earn their keep. They prevent dirty water from flowing through a clean water supply line, where it can move through your shower heads, faucets, and more. Often, they achieve this by using a single spring that opens when water pressure applies in one direction but closes to prevent water pressure from applying in the opposite direction.

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Does Installation Require Assistance From a Pro?

Installing an anti-siphon valve is an involved process. You’ll need to turn off the water supply to your home, remove any hoses and attachments from the fixture, remove the spigot, install the pipe, add the short pipe and valve, and replace the pipe so that it’s at the right angle. 

This isn’t a task for the average DIYer. It’s safer and makes much more sense to have a professional install this for you. This will save you time and give you peace of mind that your anti-siphon valve is on correctly and you have safe drinking water. 

What Should I Budget for an Anti-Siphon Valve?

The costs of anti-siphon valves vary based on the style you want. Generally, you can find these as cheap as $30 or less at many of your local home improvement stores. Keep in mind, though, that you’ll likely need to hire a plumber to handle the work for you. On that end, you’re looking at a total cost between $230 and $435.

What Can I Do to Ensure My Anti-Siphon Valve Works Well?

Proper installation is the first step to ensuring your anti-siphon valve works well. The smallest issue with installation could lead to big problems with your valve, including dirty water filtering into your system and water damage from leaks. If you hire the right pro, this shouldn't be a problem.

Keep your sprinkler heads, faucets, and all accessible outdoor irrigation components clean and clear of debris, like that from fallen leaves and tall grass. Deep clean your sprinklers and their other exterior components once or twice a year to keep all the parts in their best working order. Small problems can quickly lead to bigger issues in the overall system.

If you’ve been using your outdoor faucets heavily for a while and think there may be signs of problems from natural wear and tear, there’s an easy way you can check. Turn on the water and let it run. If you notice any unusual leaking from your outdoor faucet or sprinklers, make a note of it and call a local plumber to diagnose the problem for you. 

How Long Does an Anti-Siphon Valve Last?

Anti-siphon valves, like many home equipment, will last you 10 to 20 years with proper maintenance. Once or twice a year, you’ll want to check your valves for signs of leaking. This will be your first clue that they might be breaking down and require replacement.

Leaking occurs when debris becomes wedged into the valve or the valve experiences a faulty diaphragm. The best way to check this is to turn off any water flowing from the valve and wait a few minutes. If you return and notice water still trickling out of the valve, you’ll need to replace it. 

What Causes an Anti-Siphon Valve to Leak?

There are several culprits that could be causing this sprinkler problem. One of the more common is for debris to become wedged into the valve. When this happens, it prevents the valve from sealing all the way. In turn, you’ll notice water trickling out of your valve.

Another common problem is a worn rubber gasket. When the water supply is on, a worn gasket allows water to spray out of the valve. While the valve will still do its part in preventing backflow into your home, it’s still a water waster, and the buildup could damage your grass or plants and make your water bill skyrocket. Therefore, when you notice small leaks, you’ll want to address them promptly.