How To Blow Out Swimming Pool Lines: A Complete Winterization Guide
Blowing out swimming pool lines is the essential process of using high-volume forced air to displace water from plumbing pipes, preventing catastrophic freeze damage during the winter season. The procedure requires isolating each line, utilizing a pool-rated air compressor or blower, and sealing the lines with winterizing plugs to maintain an airtight system until the following spring.
Essential Preparation and Equipment Checklist
Successfully winterizing your pool plumbing requires more than just an air source; it demands a systematic approach to seal the hydraulic loop. Failing to remove water from low points in the plumbing can result in cracked PVC pipes, broken pump housings, and expensive structural repairs. Before beginning, ensure you have the correct tools to handle the pressures involved in clearing lines without causing back-pressure damage to your filtration equipment.
Essential Equipment:
High-volume air compressor (at least 2.0 horsepower) or a specialized pool plumbing blower.
Multi-stage pressure regulator to prevent over-pressurization of PVC (never exceed 25 PSI).
A variety of expansion winterizing plugs (threaded and rubber-gasketed) in sizes matching your returns and skimmer ports.
Teflon tape or pipe thread sealant for threaded plugs.
Shop vacuum (specifically for clearing skimmer wells).
Channel-lock pliers and a screwdriver set.
Operational Benchmarks:
Estimated duration: 2 to 4 hours depending on the complexity of the plumbing layout.
Technical prerequisite: Ability to manipulate multiport valve settings and identify the return, suction, and skimmer lines.
Safety standard: Always disconnect the power to the pump at the breaker to prevent accidental activation during the blowout process.
Procedural Workflow for Clearing Pool Plumbing
The integrity of your winterization depends on the sequence in which you displace the water. You must work from the equipment pad toward the pool, ensuring that every lateral line is cleared and sealed effectively.
Step 1: Lowering the Water Level and Initial Drainage
Before blowing air, you must lower the pool water level to approximately 6 to 12 inches below the skimmer mouth. Drain your pool pump, filter tank, and heater by opening the drain plugs located at the bottom of each component. Ensure the multiport valve is set to the winterize or waste position. If your heater has a pressure switch, remove it to prevent internal water entrapment.
Step 2: Isolating the Plumbing Lines
Use your equipment pad valves to isolate the specific lines you intend to clear. Start with the suction lines (skimmer and main drain). Attach the air source to the pump suction port or the winterizing port on your plumbing manifold. Ensure that the filter is bypassed during this process to prevent internal media damage from high-velocity air.
Step 3: Executing the Air Blowout
Activate the compressor. Watch the pool returns for a consistent stream of air bubbles followed by a steady, dry mist. Once you see air exiting the pool end, hold the pressure for approximately 30 seconds to ensure the line is thoroughly cleared of residual water.
Warning: Never exceed 25 PSI when blowing out lines. Excessive pressure can cause PVC fittings to burst, particularly in older systems where the pipe material may have become brittle over time.
Step 4: Sealing the Lines
With the air still running, insert and tighten your expansion plugs into the return jets and skimmer ports. Once the plug is secured, turn off the compressor. If you hear air escaping, immediately release the pressure and re-seat the plug to ensure a watertight seal. Move to the next line and repeat the process until all suction and return lines are isolated with plugs.
Step 5: Final Manifold and Pump Protection
After all underwater lines are plugged, remove the drain plugs from the pump and filter permanently for the season. Store these plugs in the pump basket to ensure they are available for reinstallation in the spring. Apply a thin layer of pool-grade lubricant to O-rings and gaskets to prevent them from drying out or cracking during the cold months.
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Comparative Specifications for Winterization Methods
The following table details the technical parameters required for different plumbing configurations and the corresponding equipment necessary to handle the pressure and flow requirements effectively.
| Component | Pressure Threshold (PSI) | Recommended Air Source | Sealant Requirement |
|---|---|---|---|
| PVC Return Lines | 15 - 20 PSI | High-Volume Blower | Expansion Plug / Gasket |
| Suction Lines | 10 - 15 PSI | Air Compressor | Threaded Plug / Teflon |
| Main Drain Line | 15 - 20 PSI | Air Compressor | Hydrostatic Relief Valve |
| Skimmer Throat | 5 - 10 PSI | Shop Vacuum / Blower | Skimmer Guard / Plug |
Common Site Failures and Field Fixes
Even experienced pool owners encounter challenges during the winterization process. Addressing these failures immediately prevents long-term hardware degradation.
Failure: The line will not hold air pressure.
Root Cause: A degraded rubber gasket on the winterizing plug or a hairline crack in the pipe fitting.
Actionable Fix: Inspect the plug for mineral buildup or debris. Replace the plug if the rubber is hardened. If the leak persists, check the PVC connection at the pool wall for cracks using an underwater epoxy putty.
Failure: Water continues to surge from the return jets despite high-pressure air.
Root Cause: Low point in the plumbing design where water collects.
Actionable Fix: Verify that the valve settings are correctly diverting all airflow to that specific jet. You may need a higher volume blower to lift the water column out of a subterranean dip in the plumbing.
Failure: The pump housing shows signs of freezing damage.
Root Cause: Residual water was left inside the volute or the internal seal plate.
Actionable Fix: Ensure that all drain plugs are removed and the pump is tilted to facilitate drainage. In extreme climates, remove the pump motor and housing entirely and store them in a climate-controlled area.
Frequently Asked Questions
Can I use a standard shop vacuum to blow out pool lines?
A shop vacuum is generally insufficient for large or long plumbing runs because it lacks the necessary CFM (cubic feet per minute) to move the water column. While it may work for a small, above-ground pool, in-ground systems require a dedicated pool blower or a regulated high-capacity air compressor.
Should I use antifreeze in my pool lines?
Non-toxic, propylene glycol-based pool antifreeze is recommended if you cannot remove 100% of the water from your lines. After blowing out the lines, pour the antifreeze into the pipes before inserting the winterizing plugs to protect against any small amounts of residual water that may settle at low points.
How do I know if the main drain is clear?
The main drain is clear when you observe a steady, forceful blast of bubbles emanating from the deep end of the pool. If you do not see bubbles, the hydrostatic valve may be stuck or the line may be blocked, requiring professional hydro-jetting to clear.
Does the filter need to be cleared during the blowout process?
You should bypass the filter entirely during the blowout process to prevent air pressure from damaging the filter grids or internal cartridge elements. Air should be directed through the plumbing lines, not through the filtration unit itself.
Protect Your Pool Investment Today
Regular maintenance and proper winterization procedures ensure your pool remains operational for years to come. Consult your local pool technician if your plumbing configuration includes complex features like multi-speed pumps or automated valve actuators.
