How to Drain a Pool (Safely & When You Should Do It)

When Should You Drain Your Pool?

There are a few reasons you may want to partially or completely drain your pool:

• High Cyanuric Acid (CYA): Cyanuric acid is a chlorine stabilizer. It works to protect chlorine from breaking down under sunlight. All chlorine tablets have CYA in them, so CYA levels naturally build over time. But when CYA is too high, it can actually reduce chlorine's effectiveness, potentially leading to chlorine lock (where chlorine levels may be high, but algae still forms). The only effective way to reduce CYA is to drain your pool
• Severe Algae Blooms: If an algae problem becomes unmanageable with standard shock treatment, draining may be the best option. If your pool is 'swampy', and you cannot see the bottom, it may be more cost effective and efficient to drain and refill your pool, compared to the cost of chemicals (and cleaning time) to try to shock the algae away. Check out more information about cleaning a green pool here.
• High Calcium Hardness: This is a problem specific to those living in places with hard water (shout-out to our Arizonans!). If calcium is present in high amounts in tap water, then you will continue to add calcium to your pool as you refill water that has evaporated. In Arizona, we have high calcium levels in our water, and a hot, dry climate, meaning we lose a lot of water to evaporation. As a result, calcium hardness can increase by 30% each year. Over time, this will make managing scale lines on your tile virtually impossible. Draining and refilling will reset your calcium hardness levels

What Time of Year Should You Drain Your Pool?

Draining a pool dries the pool surface and exposes the surface to the weather. As such, you should avoid draining during extreme heat.

In Arizona, we drain in the Fall, Winter, and Spring.

For plaster pools, we do not drain if the daytime highs exceed 85 degrees. For PebbleTec pools, we do not drain if the daytime highs exceed 95 degrees.

How to Drain a Pool Safely

Warning: Draining a pool improperly can cause serious damage. If you're unsure, call a professional pool service

Below we'll walk through the best way to drain a pool.

Step 1: Determine Where You Will Drain

There are several options for draining your pool, depending on your local municipality and your home:

• Sewer Cleanout: This is our preferred method and where we drain 80%+ of pools. Direct drainage to the sewer cleanout pipe. Most homes have a sewer clean-out, but not all. So check to make sure your home has one and it is accessible.
• Street: Some municipalities (e.g., Tempe, AZ) allow draining to the street if the water is clear and properly balanced. Most locations do not allow this. And even if the municipality allows it, your HOA may not, so make sure to check all relevant rules
• Yard, Wash, or Landscaping: In a dry climate like a desert, this can be an option, as it will dry quickly, although it can make a real mess of your yard for a while. For anything bigger than a small pool, it is not a realistic option. Again, be careful to ensure compliance with local authorities and any homeowner groups

Step 2: Prepare Your Pool Equipment

This is very important! Shut off all pool-related equipment, including the pump, heater, pool light. It's usually best to just shut the equipment off at the breaker, unless you are confident that you can turn the pump off and prevent it from turning on at its scheduled program.

Also make sure to turn off any auto-fill system, so that you do not waste water by filling the pool while it is draining.

Step 3: Use a Submersible Pump

• You should not drain a pool with the pool pump. It is not designed to do this. Once the water level falls below the skimmer, your pump will likely start to run dry anyways
• Use a submersible pump, which is specifically made for safely draining water
• Ideally, use a submersible pump with no more than 3,000 gallons per hour of flow (<50 gallons per minute), to minimize the risk of exceeding your sewer's capacity, which can cause backup and flooding of your home
• Position the pump in the deep end to drain all water
• Connect the sump pump via a backwash hose to your sewer clean-out or wherever you are draining your pool

Step 4: Monitor the Process

How long does it take to drain a pool? Draining a pool can take anywhere from 4 hours to 12 hours depending on the size of your pool and the power of your pump. If your pump has an auto shut-off feature, then you are safe to let it run without monitoring it. If it does not, you must keep a close eye on it so the pump does not run dry.

While rare, there is always a risk of backup to your sewer. Keep an eye on showers periodically to check for any water backing up, and shut the pump off immediately if you see this.

Step 5: Be Aware of Hydrostatic Pressure Risks

In some regions, high groundwater levels can cause an empty pool to lift or shift. This is mainly a concern in high water table areas like Florida. It's much less of a concern in a dry place like Arizona. If you have any concern about this, contact a local pool expert before draining.

Step 6: Refill

Once draining is complete, begin the refill using your tap water. Most hoses deliver 5-12 gallons per minute of water. So, for a medium-sized 15,000 gallon pool, the refill process can take anywhere from 1 to 3 days. Larger pools can take longer.

Unless you have a device attached to your hose that will automatically shut off when the water is refilled, make sure to keep a very close eye on water levels, set timers on your phone regularly to remind you to check, and never let the pool fill overnight while you are sleeping.

Step 7: Equipment Start-Up Chemical Rebalancing

Turn your equipment back on. Your filter housing and pump will be dry, so you may need to use a hose or bucket of water to get your pump to prime.

Tap water is not chemically balanced, so you will need to add chemicals. The most important chemicals to add are chlorine, as your pool will have effectively no chlorine. You should also add CYA to stabilize the chlorine, although make sure to only dose the CYA levels to the low end of the normal range (30ppm), as CYA levels naturally rise over time (as mentioned above). You may also need to adjust pH and alkalinity using acid, baking soda, and soda ash, but test the water and adjust accordingly.

Why Hire a Professional for Pool Draining?

Draining a pool incorrectly can result in costly damage. Professional services ensure:

1. Compliance with local draining regulations
2. Proper shut-off of pool equipment, including pumps, lights, heaters, and auto-flls
3. Proper use of submersible pumps
4. Water rebalancing

If you're interested in learning more, check out the Splash Mob Pool Draining Checklist, which is the checklist we provide to all customers prior to draining their pool. You can also learn more about our Drain & Refill services.