Draining water from an underground pool is a necessary maintenance task that addresses issues like chemical imbalance, algae growth, or preparing for winterization and repairs. While it shares the fundamental goal of removing water with above-ground models, the process for an underground system requires specific considerations to protect the structure and ensure safe water disposal. This guide provides a detailed, step-by-step approach to safely and effectively draining your below-ground pool without causing damage.
Preparing for the Drain
Before attaching a hose to the drain plug, a critical phase of preparation begins. You must first consult your pool manufacturer's guidelines, as specific structural recommendations for water removal vary by model and manufacturer. Unlike a permanent in-ground concrete pool, an above-ground liner relies on water pressure to maintain its structural integrity against the surrounding earth; completely emptying it can cause the walls to collapse or the liner to pull away from the frame. Therefore, understanding your pool's design limitations is the most important step in preventing catastrophic damage during the draining process.
Checking Local Regulations
Another often-overlooked aspect of preparation involves municipal regulations regarding water disposal. Many cities and counties prohibit the discharge of pool water into storm drains or public sewers due to the high chemical and salinity content, which can overwhelm treatment facilities or harm local waterways. Before you begin, contact your local public works department to confirm where you are allowed to discharge the water. Planning this outlet in advance saves you the labor of moving hundreds of gallons of water manually if a storm drain is not a viable option.
Methods for Draining Water
With permissions secured and preparations made, you can select the most appropriate method for removing the water. The approach you choose depends largely on whether your pool is equipped with a built-in pump and the slope of your yard. Below are the most common and effective techniques for below-ground models, ranging from simple gravity feed to active mechanical pumping.
1. Using the Drain Plug
The most straightforward method involves locating the main drain plug at the bottom of the pool shell. This option is only feasible if the ground where the pool sits is lower than a suitable discharge point, such as a street drain or a lower area of landscaping. To execute this, you open the plug to allow gravity to do the work; however, you should never walk away and assume it will finish unattended. You must remain present to monitor the flow rate and prevent the pool shell from losing pressure support, which can lead to structural failure.
2. Manual Siphoning
When a drain plug is unavailable, or the ground level is too high, manual siphoning becomes the most efficient tactic. You create a siphon by filling a length of hose with water and submerging both ends into the pool—once the flow starts, gravity will continue the process without further intervention. For best results, use a hose with a large diameter to move water quickly, and position the discharge end lower than the pool floor to maintain consistent flow. This method is particularly useful for reaching the final few inches of water that a drain plug might leave behind.
3. Using a Submersible or External Pump
For the fastest and most controlled drainage, a pump is the definitive solution, especially for larger volumes of water or uneven terrain. Submersible pumps are placed directly inside the pool, while external pumps use a vacuum hose to pull water out. When selecting a pump, ensure it has the capacity to handle the gallons of your pool; using an underpowered machine will result in hours of waiting and potential overheating. This mechanical approach is highly effective but requires careful cable management to prevent electrical hazards around wet surfaces.
Safety and Structural Considerations
Throughout the draining process, safety protocols must remain at the forefront to prevent accidents or long-term damage to the pool structure. The primary risk associated with draining an underground pool is the loss of hydrostatic pressure; the weight of the water normally counteracts the upward pressure of the groundwater beneath the pool shell. If the pool is empty for an extended period, this balance can shift, causing the liner to float or crack. To mitigate this, some professionals recommend partially draining the pool rather than completely emptying it, allowing the structure to retain enough water to maintain its position.
Protecting the Liner
If your pool features a vinyl or similar soft liner, extra caution is required to avoid folds or creases that can tear when the pool is refilled. As the water level drops, you should manually adjust the liner to keep it smooth against the floor. Allowing the liner to dry out for too long can cause it to shrink and become brittle, making it difficult to reinstall during refilling. Patience is key in this stage; refill the pool promptly once maintenance is complete to ensure the material retains its elasticity.
Refilling and Post-Drain Care
Once the water has been successfully removed and the necessary maintenance or repairs are complete, refilling the pool requires a specific protocol to restore optimal conditions. You should begin by filling the pool slowly, which allows the liner to re-adhere to the frame and prevents shock to the structure. As the pool fills, you must monitor the filter system and air pillows; air trapped in the lines can cause the system to chatter or fail. Finally, you will need to rebalance the water chemistry by testing and adjusting the pH and chlorine levels, ensuring the environment is safe and comfortable before swimmers return.
