How to Blow Out a Sprinkler System

It’s not fun to winterize a sprinkler system, but luckily, it’s easier than it seems. That’s especially true if you have an air compressor. Many people struggle with how to blow out a sprinkler system and find an air compressor that’s the right size for the job.

The size of the air compressor isn’t too important as long as it can provide 20 CFM to 50 CFM of air. Keep the pressure at 80 PSI if your sprinklers have PVC pipes and 50 PSI if the pipes are made of polyethylene. Oil-free compressors are great for winterizing a sprinkler system because you can easily blow out the sprinklers without having to carry a huge compressor.

Take your time and spend up to 3 minutes on each zone so you blow out all the debris and water. Follow along as we explore how to blow out a sprinkler system.

Can I Blow Out My Sprinkler System Myself?

You can blow out sprinklers without professional help, but you must be careful. For example, you can damage your sprinklers and create a huge mess of water if you don’t shut the system down before you blow it out. It can cost over $4,000 to replace a sprinkler system, so the last thing you want to do is destroy it with an air compressor when you blow it out.

Water will get trapped within your sprinklers if you don’t blow them out. The water can sit within the system and freeze throughout fall and winter. Once it freezes, the ice will expand and damage the pipes and sprinklers.

Debris such as dirt, grass, and even dead bugs can also wind up within your sprinklers. This debris can limit the flow of water and ultimately reduce the system’s performance if you don’t blow it out. There’s no need to hire a professional to blow out a sprinkler system if you have an air compressor.

How Big of an Air Compressor Do I Need to Blow Out Sprinklers?

You need at least a 20 CFM air compressor to blow out sprinklers. CFM, or cubic feet per minute, refers to how much air you can blow through the system in a minute. This is just as important as your air compressor’s PSI, or pounds per square inch.

A bigger air compressor may be necessary if the sprinkler system has big pipes. In that case, you may want to consider a 50 CFM air compressor. That is overkill for standard sprinklers with small pipes, so carefully assess the situation so you don’t damage the sprinklers.

What PSI Should You Use to Blow Out Sprinklers?

You should use between 50 and 80 PSI to blow out sprinklers with an air compressor. That said, it ultimately depends on the compressor and what your sprinkler system is made of. Sprinkler systems are typically made of either PVC or polyethylene pipes.

PVC is rated to withstand pressure better than polyethylene in most cases. Because of that, you can safely blow out sprinklers with PVC pipes at up to 80 PSI. This provides enough power to remove debris within the system without bursting the pipes.

Polyethylene sprinkler pipes require 50 PSI. Never use too strong of an air compressor to blow out polyethylene sprinklers or you can damage the system.

How Long Does It Take to Blow Out Sprinklers?

It takes up to 30 minutes to blow out sprinklers with an air compressor. That said, the timing ultimately depends on how many zones your sprinkler system has. Most properties have at least 6 sprinkler zones, but large properties have up to 9 or more zones.

You can expect it to take 2 to 3 minutes to blow out each sprinkler zone. It can be tedious, but you must blow out each zone one at a time. Move on to the next zone when no more water comes out of the sprinkler head.

This tells you that no more water is stuck in the sprinkler system. It’s important to keep using the air compressor until no more water comes out, or else the sprinklers may freeze during winter. The compressed air will force the water out and turn whatever is left into a mist that dissipates quickly.

How to Blow Out Sprinklers

It’s easy to blow out sprinklers with an air compressor, but you must follow the steps. Let’s look at the key steps it takes to safely blow out a sprinkler system with an air compressor.

1. Turn the Lines Off

You can only safely blow out sprinklers with an air compressor if you turn the lines off. Turn off the isolation valve to shut off the water supply. Next, put a bucket beneath the faucet near the isolation valve to catch water.

Open the faucet and drain the water into the bucket. This only takes a few minutes, and it will eliminate most of the water from the main line. Repeat this process with the valve for each zone as you go along. Many people simply open the valves one at a time after they blow out the sprinklers in each zone, but you can preemptively open each valve before you start if you want.

The best option is to start with the furthest zone and work your way back up toward the main line. Turn off the sprinkler system’s timer from the control panel before you move on. That ensures that the electrical components of the system won’t run throughout fall and winter.

2. Hook Up the Air Compressor

Once the timer is off and the lines are disconnected, you must hook up the air compressor. Find the sprinkler system’s blowout port. Each zone within the system has a blow-out port in the piping. You can only connect the air compressor to the port if you have a blow-out adapter.

Luckily, this part only costs $10 to $15 in most cases. Attach the adapter to your air compressor and it hook it up to the blowout port. Make sure the connection is tight, so air, water, and debris don’t leak.

3. Blow Out the Sprinklers in Each Zone

Now, it’s time to blow out the sprinklers with your air compressor. One by one, connect the compressor to the valve for each zone. Turn the air compressor and set it to 50 to 80 PSI depending on what material the pipes are made of and how much pressure they’re rated for.

You’ll know it’s working when water starts to come out of the sprinkler head. Let the compressor run for up to 3 minutes or as long as it takes for water to stop coming out of the system. Turn off the compressor, disconnect it, shut the valve, and repeat the process for each zone.

Do You Need an Air Compressor to Blow Out a Sprinkler System?

You need an air compressor to blow out a sprinkler system unless it has an automatic drain system in some cases. That said, it helps to use an air compressor in conjunction with an automatic drain system. These systems are useful, but they don’t always work as intended.

Water can remain within them in some cases, especially if there is debris in the pipes, valves, or sprinkler heads. Automatic drainage systems detect the pressure within them and drain water as soon as the level drops. This doesn’t eliminate the need for an air compressor, but freezing and blockages are less common with automatic drainage systems.

Otherwise, you can simply shut down the main line, open it, drain it into a bucket, and then turn one head on. That will let the system drain automatically without too much pressure building up. It’s easier to winterize a sprinkler system with an automatic drainage system, but they aren’t always ironclad.

What Type of Air Compressor is Best to Blow Out Sprinklers?

Oil-free air compressors are typically the best to blow out sprinklers. Sure, they are much louder than oil-injected air compressors, but they are also much lighter. The portability of oil-free air compressors makes them more practical for blowing out sprinklers. That said, they don’t last as long as oil-injected compressors and airflow problems are more common with them.

So, What Size Air Compressor Do I Need to Blow Out Sprinklers?

You need a portable air compressor with a flow rate of 20 CFM to 50 CFM. Large pipes can handle 50 CFM whereas smaller pipes require 20 CFM so too much pressure doesn’t build up. Stick to 80 PSI when you blow out PVC pipes and 50 PSI for polyethylene pipes. Start with the furthest sprinkler zone and move backward as you blow out the line in each zone.

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