How To Blow Out Inground Pool Lines – A Step-By-Step Guide
Closing your pool for the season can feel like a daunting task, especially when you worry about frozen pipes cracking under the pressure of winter ice. You want to ensure your backyard oasis survives the freeze so it’s ready for the first warm day of spring. Learning how to blow out inground pool lines is the most critical skill for any pool owner looking to save money and protect their investment.
I promise that by following this guide, you will gain the confidence to clear your plumbing like a pro. You will understand the exact sequence of steps, the specific tools required, and the safety measures that prevent expensive repairs. We will walk through the entire process together, from lowering the water level to creating a vacuum seal that keeps your lines dry all winter long.
In this article, we will cover the essential equipment list, the “air lock” technique for main drains, and how to handle skimmers and return lines. Whether you are a first-time pool owner or a seasoned DIY enthusiast, these practical tips will help you master the art of pool winterization. Let’s get your pool ready for the big freeze.
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Why You Must Learn how to blow out inground pool lines Properly
Water expands by approximately 9% when it freezes. In a rigid PVC pipe buried underground, that expansion has nowhere to go but out, leading to catastrophic pipe failure. Repairing a burst line under a concrete pool deck can cost thousands of dollars and ruin your summer plans.
Blowing out the lines ensures that no standing water remains in the plumbing. By replacing that water with air, you create a buffer zone. Even if moisture remains, the air provides space for expansion without putting stress on the pipe walls.
This process is about more than just avoiding cracks; it is about longevity. Properly winterized pipes last longer and maintain better pressure throughout the life of the pool. It is the ultimate preventative maintenance for any outdoor enthusiast who values self-sufficiency and smart home management.
Essential Tools and Gear for a Successful Blowout
You cannot effectively clear pool lines with a standard air compressor used for tires. Those machines provide high pressure (PSI) but very low volume (CFM). For a pool, you need high-volume air to push large amounts of water through 1.5-inch or 2-inch pipes.
The gold standard is a dedicated pool blower, often called a “Cyclone” blower. These machines are designed specifically for this task and provide the steady, powerful airflow needed to clear deep lines. If you do not want to buy one, many local hardware stores offer them as daily rentals.
A powerful wet/dry shop vacuum can work for some shallow lines, but it often lacks the “oomph” to clear a main drain located at the bottom of a deep end. You will also need a variety of winter plugs, including rubber expansion plugs and threaded plugs with O-rings, to seal the lines once they are clear.
Finally, keep a Gizzmo or a similar skimmer compensator on hand. This is a hollow plastic tube that screws into your skimmer. It absorbs the pressure of ice forming inside the skimmer well, protecting the plastic housing from cracking during a hard freeze.
Step-by-Step Guide on how to blow out inground pool lines
Before you begin, ensure your pool water is chemically balanced and the water level is lowered. Most experts recommend dropping the water level to about 4 to 6 inches below the lowest return line or skimmer mouth. This prevents water from splashing back into the lines while you work.
- Drain the Equipment: Start at the equipment pad. Turn off the power to the pump and heater. Remove the drain plugs from the pump housing, the filter tank, and the heater. Store these plugs in the pump basket so you do not lose them.
- Set the Multiport Valve: If you have a sand or DE filter, set the multiport valve to the “Recirculate” position. This allows air to bypass the filter media and go directly into the lines. For cartridge filters, remove the internal cartridge and reassemble the tank.
- Connect the Blower: Attach your blower hose to the pump’s strainer pot or the skimmer line. Most pros connect at the pump because it is the central hub of the plumbing system. Use a threaded adapter to ensure a tight, airtight seal at the connection point.
- Clear the Skimmers First: Turn on the blower. You will see water bubbling out of the skimmers. Once only air is coming out, quickly insert your Gizzmo or expansion plug. This seals the line while air pressure is still active, ensuring no water creeps back in.
- Blow Out the Return Lines: Close the valve to the skimmer and open the valves to the return lines. Air will begin to bubble out of the wall jets. Start with the jet closest to the pump and work your way to the furthest one.
- Plug the Returns: As each return line starts blowing a steady mist of air, insert a winter plug. Tighten it firmly. You may need a helper to hold the plug in place while you tighten the wing nut to prevent it from popping out under pressure.
Once all the wall returns are plugged, you have successfully cleared the most vulnerable parts of your system. However, the most challenging part—the main drain—still requires a specific air lock technique to ensure it remains safe throughout the winter.
Managing the Main Drain and Creating an Air Lock
The main drain is located at the deepest point of your pool. Because it is so deep, you cannot easily plug it from the surface. Instead, we use the physics of air pressure to create what is known as an air lock. This prevents water from rising back up the pipe to the freeze zone.
With all other lines plugged, direct all the blower’s air toward the main drain line. You will eventually see a massive eruption of bubbles at the bottom of the pool. This indicates that the air has pushed the water all the way down the pipe and out the drain grate.
While the air is bubbling vigorously, quickly close the main drain valve at the equipment pad. This “locks” the air inside the pipe. Since the air has nowhere to go, it stays in the pipe, holding the water level deep underground where the earth’s natural heat prevents it from freezing.
Think of it like holding your finger over the top of a straw. The water stays out because the air is trapped. This is a critical step for off-grid explorers or homesteaders who live in extreme northern climates where the frost line can reach several feet deep.
The Role of Pool Antifreeze in Winterization
Even with a perfect blowout, a small amount of residual moisture can settle in low spots or “bellies” in the PVC piping. To add an extra layer of security, many outdoor enthusiasts use non-toxic pool antifreeze. Never use automotive antifreeze, as it is highly toxic to humans and the environment.
Pool antifreeze is usually propylene glycol-based and is safe for your filtration system. After you have blown out the lines and plugged the returns, you can pour a gallon or two into the skimmer lines. This ensures that any water that manages to seep past a plug stays in a liquid state.
This is particularly useful for complex plumbing setups with multiple valves and long runs of pipe. If you are unsure if you got every drop of water out, the antifreeze acts as your insurance policy. It is a small price to pay for total peace of mind during a blizzard.
Common Pitfalls to Avoid During the Winterization Process
One common mistake is failing to remove the directional eyeballs from the return jets. These plastic fittings restrict airflow and make it difficult to get a tight seal with a winter plug. Always unscrew the decorative rings and remove the eyeballs before you start the blower.
Another error is rushing the process. You must see a constant stream of air (dry air, not a mist) before you plug the line. If you plug it too early, you are trapping water inside. Take your time and listen to the sound of the blower; it will change pitch when the line is finally clear of water.
Finally, do not forget the secondary equipment. If you have a booster pump for a pool cleaner, a salt cell, or a chlorinator, these must also be drained and blown out. Many pool owners focus on the main lines but forget these expensive components, only to find them cracked in the spring.
Frequently Asked Questions About how to blow out inground pool lines
Can I use a shop vac to blow out my pool lines?
A high-powered shop vac (6.5 peak HP) can often clear skimmers and shallow return lines. However, it usually lacks the static pressure required to push water out of a deep-end main drain. For the best results and total safety, a dedicated pool blower is recommended.
Do I need to blow out the lines if I live in a mild climate?
If your area experiences even a few nights of sub-freezing temperatures, you should blow out your lines. It only takes one hard freeze to crack a pipe. If you prefer to keep the pool open, you must run your pump continuously during freezing weather to keep the water moving.
How do I know if my winter plugs are leaking?
After plugging the lines, you can spray a little soapy water around the edge of the plug. If you see bubbles forming, air is escaping, which means water could eventually get back in. Tighten the plug or check the O-ring for debris and reseal it immediately.
Should I put antifreeze in the pump and filter?
Generally, no. You should drain the pump and filter by removing the drain plugs and leaving them open (or storing the plugs in the basket). Antifreeze is best used in the underground plumbing lines where you cannot physically see if all the water is gone.
Final Thoughts on Protecting Your Pool for Winter
Mastering the process of winterization is a rite of passage for any self-reliant homeowner. When you know how to blow out inground pool lines, you take control of your property’s maintenance and avoid the stress of “what-if” scenarios during the winter months.
Remember to work systematically, use the right high-volume equipment, and never skip the air lock on the main drain. By being meticulous and safety-first, you ensure that your pool remains a source of joy rather than a source of repair bills. Take your time, double-check your plugs, and rest easy knowing your pipes are dry and safe.
Stay prepared, stay proactive, and enjoy the peace of a well-protected homestead. We will see you back in the water when the sun returns!
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