Preparing your above ground pool for the cold months is a critical step in protecting your investment and ensuring a smooth reopening in the spring. While the standard advice often focuses on simply covering the pool, the specific process of winterizing with a bottom drain adds a layer of essential protection against freezing damage. This component, designed to pull water from the base of the pool, requires specific attention to prevent remaining water inside the drain line from expanding and destroying the pipe or fittings.
Above ground pools face unique challenges during winter, primarily the pressure exerted by groundwater on the walls as the pool shell loses its water’s buoyant support. When water is left in the plumbing and the drain, it can freeze, expand, and crack fittings, rendering the pump and filter system useless by the time warm weather returns. A meticulous winterization process that addresses the bottom drain is one of the most effective ways to prevent this type of costly structural and equipment failure.
Understanding the Role of the Bottom Drain
The bottom drain is more than just a plug on the pool floor; it is a crucial component of the circulation system. Connected directly to the return line leading to the filter and pump, it utilizes the principle of vacuum to pull sediment and fine debris that sinks to the bottom. During winterization, this same connection becomes a vulnerability. Any water trapped in the pipes leading to and from the drain valve can freeze, expand, and cause significant damage.
The Freezing Risk and Potential Damage
Water expands by approximately 9% when it freezes. In a rigid PVC pipe or a metal fitting, this expansion creates immense pressure that has nowhere to go but outward. This force can crack pipes, blow out fittings, and even damage the actual drain fitting on the pool shell itself. Repairing these issues often requires cutting out and replacing sections of pipe or entire fittings, which is both time-consuming and expensive. Addressing the drain is not an optional step; it is a mandatory safeguard.
Step-by-Step Winterization Process
To effectively winterize your above ground pool using the bottom drain, you must follow a specific sequence of steps to remove all water from the plumbing system. The goal is to eliminate any water that could linger inside the pipes, hoses, and the drain line itself.
1. Lower the Water Level
Before you can even think about the drain, the water level must be reduced. Using a submersible pump or a manual siphon, lower the water to a point where it is at least 6 to 12 inches below the bottom of the skimmer. This ensures that when you open the main drain valve, the water will drain out effectively rather than simply reaching a point where gravity can no longer pull it through.
2. Backwashing and Preparing the Filter
Turn off the pump and set the multiport valve to the "Waste" or "Backwash" position. This step removes trapped dirt from the filter media and clears the plumbing lines. Run the pump until the flow from the waste line is clear. After shutting the pump off, remove the drain plug from the pump strainer pot and allow any residual water to fully drain out of the impeller and housing.
Draining the Plumbing System via the Bottom Drain
With the water level lowered and the filter prepared, you can now focus specifically on the bottom drain lines.
| Step | Action | Purpose |
|---|---|---|
| 1 | Locate the cold water return lines. | Identify the pipes that connect to the skimmer and main drain. |
| 2 | Remove the return lines from the skimmer and floor fittings. | Gravity will pull water out of the higher pipes. |
| 3 | Open the bottom drain valve on the pool wall. | Allows the water sitting on the pool floor to exit. |
| 4 | Tilt the return lines to ensure the last of the water drains. | Removes water trapped in the high points of the plumbing. |
| 5 | Cap or plug the exposed return lines. | Prevents critters from nesting inside the pipes and blocks debris. |
Protecting the Drain Fitting and Final Checks
Once the majority of the water is removed, you should address the drain fitting on the pool structure itself. If your pool uses a simple threaded plug, remove it completely and store it indoors for the winter. If it is a sealed, non-removable drain, you must ensure the internal bladder or gasket is not compressed under pressure. Leaving the plug in place while the water inside freezes will often split the housing.
After the lines are clear, take a moment to inspect the area around the bottom drain for any cracks or tears in the vinyl liner. Small punctures may have occurred during vigorous vacuuming. While you are looking, you can also apply a vinyl protectant to the surrounding area to guard against the drying effects of winter sun and cold. Cover the pool with a sturdy winter cover, ensuring the cover's anchor points do not puncture the liner near the drain area, and you will be ready for a hassle-free spring restart.
