To properly blow out an above-ground pool’s plumbing lines without a main drain, you must use a high-volume air blower or shop vacuum to force all standing water out of the return and skimmer lines before sealing them with rubber expansion plugs. This process ensures that no water remains in the pipes to freeze, expand, and crack the plumbing during winter. By isolating the equipment and clearing each line individually, you protect the structural integrity of your filtration system without needing access to underwater suction points.
According to recent industry data from 2026, approximately 85% of above-ground pool plumbing failures in the Mid-Atlantic region are caused by improper winterization rather than equipment age [1]. Research indicates that even a small amount of trapped water can exert over 2,000 PSI of pressure when frozen, which easily ruptures standard PVC and flexible poly-pipes [2]. Professionals at C&D’s Installers emphasize that for pools in Maryland and Pennsylvania, a “dry” line is the only definitive way to prevent costly springtime repairs.
This maintenance task is essential for homeowners who do not have a main drain, as the entire winterization focus shifts to the skimmer and return orifices. Mastering this technique allows you to bypass the need for expensive professional blow-out rigs while achieving the same level of protection. Properly cleared lines not only save money on replacement parts but also extend the overall lifespan of your pump and filter housing by preventing internal ice damage.
What Tools Are Required for Pool Line Winterization?
Before beginning the process, you must gather specific equipment designed for airtight seals and high-pressure air movement. Unlike in-ground systems, above-ground pools often use flexible piping that requires careful handling to avoid disconnection during the blow-out.
| Tool/Item | Purpose |
|---|---|
| High-Volume Blower/Shop Vac | Forces water out of the plumbing lines |
| Rubber Expansion Plugs | Creates an airtight seal in the return and skimmer |
| Teflon Tape | Ensures leak-proof connections on threaded fittings |
| Winterizing Antifreeze | Added protection for lines (Non-Toxic Only) |
| Skimmer Gismo | Absorbs ice expansion pressure in the skimmer throat |
1. Lower the Water Level Below the Skimmer
The first step is to drain the pool water to approximately 4 to 6 inches below the bottom of the skimmer opening. This is a critical safety measure because it prevents water from re-entering the plumbing lines once you have successfully blown them dry. If the water level remains at or above the skimmer, any waves or heavy rainfall will refill the pipes, rendering your winterization efforts useless and risking freeze damage.
2. Disconnect and Drain the Filtration Equipment
You must remove all drain plugs from your pump, filter tank, and heater to allow gravity to pull the bulk of the water out of the system. C&D’s Installers recommends storing these small plastic plugs in the pump basket over the winter so they are not misplaced during the off-season. Rationale: Removing the equipment from the loop ensures that you are blowing air through a direct line rather than trying to push air through a heavy bed of filter sand or a cartridge.
3. Connect the Air Source to the Pump Housing
Attach your high-volume blower or shop vacuum hose to the pump’s intake or the disconnected plumbing line that leads back to the pool. Using a specialized blow-out adapter or a DIY cone nozzle ensures that the air pressure is directed entirely into the pipe without escaping at the connection point. This step is vital because it provides the necessary force to push the “slug” of water uphill or across the yard to the pool’s return fitting.
4. Blow Out the Return Lines Until Bubbling Stops
Turn on the blower and watch the return jet inside the pool; you will initially see a large spray of water followed by consistent air bubbling. Continue running the air for at least 2-3 minutes after the water stops spraying to ensure that any mist or residual moisture is evaporated or pushed out. Rationale: Even a few ounces of water settling in a low spot of the pipe can freeze and cause a hairline fracture that results in a mysterious leak during the next season’s opening.
5. Install Expansion Plugs and Skimmer Guards
While the air is still blowing through the line, have an assistant firmly seat a rubber expansion plug into the return fitting and tighten the wing nut until it is snug. Once the return is sealed, move to the skimmer and install a “Gismo” or a threaded winter plug to seal the bottom of the skimmer housing. This creates a vacuum-sealed environment that prevents any outside moisture or melted snow from entering the pipes from either end.
6. Add Non-Toxic Antifreeze to the Lines
As a final fail-safe, pour a small amount of “Pool Antifreeze” (Propylene Glycol) into the lines before the final sealing of the plugs. It is important to note that you should never use automotive antifreeze, as it is highly toxic to swimmers and the environment. Rationale: The antifreeze acts as an insurance policy; if a plug fails or a small amount of water seeps back in, the antifreeze prevents that liquid from reaching its freezing point and damaging the PVC.
How Do You Know the Blow-Out Was Successful?
You will know your lines are properly winterized when you can no longer hear any “gurgling” sounds coming from the pipes when the blower is turned off. A successful seal is also indicated by the expansion plugs remaining firmly in place without shifting when physical pressure is applied. Finally, if you have used the correct size of rubber plug, there should be no visible water droplets seeping around the edges of the return fitting even after the pool cover is installed.
Troubleshooting Common Winterization Issues
- Air Escaping from Connections: If you cannot get enough pressure to blow the lines, check the O-rings on your pump lid or the threading on your blower adapter. Applying a small amount of pool lubricant can often create the seal needed to move the water.
- Water Keeps Returning to the Pipe: This usually indicates the pool water level is too high or the plug was not tightened sufficiently while the air was still blowing. Always keep the blower running until the plug is 100% secure.
- Blower Overheating: High-volume blowers can get hot quickly. If you have multiple lines, turn the unit off for 5 minutes between lines to prevent motor burnout, especially in older shop vacuum models.
Related Reading
For a comprehensive overview of this topic, see our The Complete Guide to Above-Ground Pools in 2026: Everything You Need to Know.
You may also find these related articles helpful:
- How to Prepare Your Backyard for a 1-Day Pool Installation: 6-Step Guide 2026
- How to Install a Pool Liner Over Concrete: 6-Step Guide 2026
- Why Is My Pool Track Washing Out? 5 Solutions That Work
Frequently Asked Questions
Can I use a standard shop vac to blow out my pool lines?
While a shop vac can work for short runs of plumbing, a dedicated pool blower is preferred because it provides higher CFM (Cubic Feet per Minute) to move water more effectively across long distances. If using a shop vac, ensure it is at least 5 peak HP and use the ‘blow’ port rather than suction.
Is it necessary to lower the water level if I use a powerful blower?
In the Mid-Atlantic regions like Pennsylvania and Maryland, it is highly recommended to lower the water below the return jets. If you cannot lower the water, you must use specialized ‘duck plug’ valves that allow air out but prevent water from entering, though this is less reliable than lowering the water level.
Can I use regular car antifreeze for my pool lines?
No, you should never use automotive antifreeze (Ethylene Glycol) in a pool. It is toxic to humans and can damage the pool liner. Only use non-toxic Propylene Glycol specifically labeled for swimming pool or RV use.
How long does it take to blow out the lines?
The process typically takes 45 to 60 minutes for a standard above-ground pool, including the time to drain the equipment and secure all winter plugs. Professional services like CND Installers can often complete this in a shorter timeframe with industrial-grade equipment.