Getting ready for winter means you'll eventually have to use an air compressor blow out pool lines before the first hard freeze hits your neighborhood. It's one of those maintenance tasks that sounds a bit intimidating if you've never done it, but once you get the hang of the rhythm, it becomes a standard part of the end-of-season routine. The goal is simple: get every drop of water out of those PVC pipes so they don't crack when the temperature drops.
If you leave water in the lines, it expands as it turns to ice. That expansion can split pipes underground, and trust me, digging up your deck to fix a leak in the spring is a nightmare you want to avoid. Using air is the most reliable way to ensure those pipes stay dry and intact until the sun comes back out next year.
Getting the right equipment ready
Before you go dragging any old machine out of the garage, you need to make sure your air compressor is actually up to the task. A lot of people make the mistake of thinking they need high pressure, but that's actually the opposite of what you want. You don't need 100 PSI; in fact, hitting your pool plumbing with that much pressure is a great way to blow out a seal or crack a fitting.
What you really need is volume. In the world of compressors, this is measured in CFM (Cubic Feet per Minute). You want a compressor that can push a lot of air consistently. A small pancake compressor can work, but you'll be waiting for the tank to refill constantly. If you can get your hands on something with a larger tank or a higher CFM rating, the job will go a lot faster.
You'll also need a few specific attachments. Most people use a specialized blow-out plug that threads into the pump basket drain or a modified "Christmas tree" fitting that can connect your air hose to the pool's plumbing. Having a good set of rubber winterizing plugs (the ones with the wing nuts) and maybe some pool antifreeze is also essential to finish the job right.
Setting up the air compressor
First things first, you need to prep the pool. Usually, this means backwashing the filter one last time and then draining the water level below the skimmer mouth. Once the water is down, go ahead and drain your pump, filter, and heater. There are usually small drain plugs at the bottom of each piece of equipment. Keep these in a safe spot—I usually toss mine in the skimmer basket so I don't lose them over the winter.
Now, connect your air compressor to the system. The easiest spot is usually at the pump. You can take the lid off the pump basket and plug the air line into the drain port at the bottom, or use an adapter on the pump's intake.
Pro tip: Keep the pressure regulator on your compressor set low. You really shouldn't need more than 5 to 10 PSI to move the water. It's the constant flow of air, not the raw force, that clears the lines. If the air isn't moving, check for a closed valve before you even think about cranking up the pressure.
Blowing out the skimmers and returns
I always like to start with the skimmer lines because they're usually the closest to the equipment pad. Open the valve for the skimmer and close off everything else (the main drain and the return lines). Turn on the compressor and wait. You'll hear some gurgling, and then eventually, a massive spray of water will erupt from the skimmer.
Let the air run until it's just a fine mist or purely air coming out. Once it's clear, shove a rubber plug or a "Gizzmo" (those long plastic tubes) into the hole at the bottom of the skimmer and tighten it down. This prevents any rainwater or snowmelt from getting back into the pipe during the winter.
Next, move on to the return lines—the jets where the water usually flows back into the pool. You'll follow the same process: open the valve for the returns and close the others. You might have three or four jets, and the air will naturally go to the one with the least resistance. As each one starts blowing nothing but air, plug it up and move to the next. It's like a game of Whac-A-Mole, but with plumbing.
Dealing with the main drain
The main drain is the one at the very bottom of the deep end, and it's the part that stresses people out the most. Since you can't exactly dive down there and put a plug in it while the pool is full, you have to use a trick called an "airlock."
Switch your valves so the air is directed only toward the main drain. You'll see big, rolling bubbles start to burp up from the bottom of the pool. Let this run for a good minute or two to make sure the water is pushed as far down the pipe as possible.
While the air is still blowing and the bubbles are active, quickly close the valve at the equipment pad. This "locks" the air in the pipe. Because the air is trapped, the water can't rise back up into the section of the pipe that's above the frost line. It's a bit of physics magic that keeps your pipes safe even without a physical plug at the bottom.
Don't forget the peripheral equipment
If you have a heater, a chlorinator, or an Alpine slide, these need attention too. Heaters are notorious for holding onto "pockets" of water in their copper headers. I usually run air through the heater separately just to be sure. Most heaters have a pressure switch or a small internal bypass that can trap water, so check your owner's manual to see if there's a specific drain-down procedure.
For chlorinators, make sure you've removed any leftover tablets and rinsed the canister out. Chemicals left sitting in a dry pipe all winter can get pretty nasty and might even damage the plastic.
Final checks and antifreeze
Once everything is plugged and airlocked, I like to do one final walkthrough. Double-check that every plug is tight. If you see bubbles escaping from a plugged return jet, it's not sealed, and you need to redo it.
Some people like to pour a bit of non-toxic pool antifreeze into the lines before plugging them as an extra layer of insurance. It's not always strictly necessary if you did a perfect job with the air compressor, but it provides peace of mind. Just make sure you use the pink stuff (Propylene Glycol) specifically made for pools and RVs—never use automotive antifreeze, which is toxic and will ruin your pool water.
Common mistakes to avoid
One of the biggest mistakes I see is people rushing the process. If you stop blowing air the second you see the water stop splashing, there might still be a significant amount of water sitting in a low spot of the pipe. Give it an extra thirty seconds of "air only" time to be sure.
Another thing is neglecting the pump itself. Even after blowing the lines, a little water can settle in the bottom of the pump housing. I usually take the drain plugs out and leave them out all winter, or even bring the pump indoors if I'm feeling particularly ambitious.
Lastly, watch your gauges. If you see the pressure spiking on your compressor but no air is coming out of the pool, turn it off immediately. You likely have a valve closed, and you don't want to find out the hard way where the weakest link in your plumbing is.
Wrapping it up
Taking the time to use an air compressor blow out pool lines is probably the most important thing you can do for your pool's longevity. It might take an hour or two on a Saturday afternoon, but compared to the cost of replacing burst pipes, it's time well spent. Once the lines are clear, the plugs are in, and the equipment is drained, you can throw the cover on and head inside, knowing your pool is tucked in safely for the winter. Just remember: low pressure, high volume, and don't stop until you see the mist turn to air.