When Should You Drain Your Swimming Pool? A Complete Guide for Pool Owners

Draining a swimming pool might seem like a straightforward fix for murky water or stubborn stains, but it’s actually one of the most consequential maintenance decisions you can make. Drain it for the wrong reason, and you could be facing thousands of dollars in structural repairs—or even a “popped” pool shell. As a pool owner, understanding when a full drain is truly necessary—and when a simpler solution will do—is essential for protecting your investment and ensuring the long-term health of your pool.

The Golden Rule of Pool Draining: Only When Necessary

The most important rule of pool maintenance is this: Do not drain your pool unless you absolutely have to. The water in your pool is not just for swimming; it plays a critical role in the structural stability of the entire pool. The weight of the water balances the pressure on the pool walls and floor, and without it, the ground can push up from underneath, potentially causing the pool to “pop” out of the ground, or causing a vinyl liner to shrink and wrinkle .

If you maintain your pool properly, a full pool water replacement may only be necessary once every 5 to 10 years . Before considering a full drain, ask yourself if a partial drain (one-third to one-half of the water) could achieve the same results. This approach is often sufficient for lowering chemical levels and is far less risky for your pool’s structure .

Key Reasons You Might Need a Pool Drain

So, when does it become necessary to call a professional pool drain service? Here are the most common and valid reasons for a complete drain:

1. High Levels of Total Dissolved Solids (TDS) or Cyanuric Acid

Over time, chemicals and contaminants build up in your pool water and can no longer be filtered out. When the TDS (the total amount of “stuff” dissolved in the water) becomes too high, it can interfere with your pool’s chemistry and make the water feel harsh. More often, the stabilizer (cyanuric acid) builds up to levels that render chlorine ineffective. The only solution for this is a swimming pool and refilling with fresh water.

2. Making Necessary Structural Repairs

If your pool needs significant repairs, a full drain is unavoidable. This includes projects like resurfacing the pool’s plaster, replacing a vinyl liner, or repairing cracks in the pool shell . In these cases, the pool must be emptied to allow contractors to work on the surface.

3. Severe Stains or Algae Infestations

While most algae can be killed with heavy shocking and algaecides, a severe, long-term infestation can embed itself into the pool’s surface. Similarly, persistent stains that don’t respond to chemical treatment may require an acid wash, which necessitates draining the pool to safely clean the plaster .

4. To Perform an Acid Wash

An acid wash is a deep-cleaning procedure used to remove stubborn stains and calcium deposits from a pool’s plaster. This is a chemical-intensive process that can only be done on an empty pool .

Critical Considerations Before You Drain

Before you start pumping water, there are several crucial factors to consider. Ignoring these steps can lead to environmental fines or serious damage to your property.

1. Understand the Risks to Your Pool Type

The risk of damage when draining depends largely on the type of pool you have :

• Concrete Pools: Generally stable when empty, but it is critical to open the hydrostatic relief plugs in the floor (often found in the main drain). This prevents groundwater pressure from pushing the pool shell out of the ground.
• Vinyl Liner Pools: These are the most vulnerable. A full drain can cause the liner to relax, shrink, wrinkle, or shift, potentially ruining it and requiring a costly replacement.
• Fiberglass Pools: Usually safe for short periods, but the pool can shift or “pop” if there’s a high-water table.

2. Check the Weather

Never drain your pool before, during, or immediately after heavy rain. A rainstorm can raise the water table, dramatically increasing the risk of your pool floating out of the ground. It’s best to plan your drain for a warm, dry period when you can keep the pool empty for the shortest possible time.

3. Find a Legal Place for the Water

This is one of the most critical steps. Draining chlorinated pool water into the street, storm drain, or a local waterway is often illegal and harmful to the environment. The chemicals (chlorine, algaecides, and salts) are toxic to fish and other aquatic life . You typically have two legal options for disposal:

• Your Own Yard: You can often drain the water onto your lawn or landscape, provided the chlorine is neutralized. Let the water sit for a week to allow chlorine to dissipate, or use a chemical neutralizer. Move the hose frequently to prevent erosion or flooding.
• The Sanitary Sewer: In some areas, you may be permitted to drain pool water into your home’s sanitary sewer cleanout. However, this must be done at a slow, controlled rate (often no more than 12 gallons per minute) to avoid backing up the sewer line into your house .

Conclusion: To Drain or Not to Drain?

Draining your pool is a significant undertaking with serious consequences for both your wallet and the environment. For most chemical imbalances, a pool draining service will tell you that a partial drain is often the safer and more effective solution. In Las Vegas, where pool draining Las Vegas options may be regulated, it’s even more important to consult with a professional. They can advise on the best course of action for your specific pool type, test your water accurately, and ensure the process is done safely and legally, protecting your pool for years to come.