How to Drain a Pool Safely: A Complete Guide

It may seem intuitive to drain a pool every time it has a problem. Whether there's a possible pool leak, unbalanced chemicals, or too many leaves backing up in the filter, you can just drain the pool and start over, right? Well, it turns out that this is not always—if ever—the best tactic. Knowing how to drain a pool and when to do it is not only safe for your pool's structure, but can also save you a whole lot of money. Here’s what you need to know about draining your above- or inground pool.

When Should You Drain Your Swimming Pool?

The water in your pool plays a larger role in its stability than you may have realized. Whether you have an inground or above ground pool, the water balances the temperature and pressure throughout its structure. 

A pool full of water protects above-ground liners from heating up and inground pool walls from literally "popping" out of place. Water even keeps some of your pool's electrical elements, such as the lights, from overheating.

Additionally, your town may set strict rules about when and where you can drain a pool. Pools drained on rainy days can overwhelm the sewer systems, for example.

All this being said, you should only drain your pool when:

• You need to make necessary pool repairs and an expert recommends a full drain.

• You've decided to invest in the cost of resurfacing your pool or replacing the liner.

• You are winterizing your pool and removing a small amount of water.

• The chemicals in your pool are highly unbalanced and require a fresh start.

• Your local municipality gives you the green light to drain.

• It’s a relatively dry week that won’t get too hot.

• When the ground is unfrozen and not at risk of frost.

• When you have at least 48 hours when you do not need your pool.

Preparing to Drain a Pool

You'll need to do a bit of research—both into the laws of your town and your pool's structure—to know how to drain your pool without damaging it. In most cases, you can drain a pool with a hose and sump pump, but you may have other options depending on your pools system

1. Check Local Laws

Again, your municipality sets pool-draining laws to prevent erosion, water contamination, and storm drain overflow. Your town may specify how to test your water's pH before draining to avoid sending heavily treated water into the ground and local water sources. If you live in an area experiencing a drought, you may also find restrictions on the time of year you can refill a pool.

2. Get to Know Your System

In the best-case scenario, you still have access to your above ground pool's user manual or can chat with a local pool expert to learn the parts of your inground pool. It's important to locate all the proper valves, hoses, and drains before starting.

Not all pools are designed the same. Some inground pools have mainline drains at the bottom of the pool for draining. You may also find a series of hydrostatic drains covered with plastic or plaster drains at the bottom of your pool. These drains allow groundwater to flow evenly as you drain your pool and change the pressure against the ground. You'll open these midway through the drainage process. If you don't, the water and earth could push and break through your pool, causing severe structural damage—a huge pool headache known as "pool pop."

3. Purchase the Right Equipment

Rent or buy a submersible sump pump to remove the water from your pool without a mainline drain. You may also need a longer garden hose so you can legally drain the water into either a sewer line—where the water can go through a treatment plant—or into an erosion-proof area. In some cases, you'll also need an adapter to attach the hose and sump pump.

Step-by-Step Guide to Draining a Swimming Pool

Once you've found the best day to drain your pool, get all your tools ready and review the user manual one last time for any tips. 

How to Drain an Above Ground Swimming Pool

Draining an above ground pool is a bit simpler than an inground one, but you can still encounter issues. Remember, the water is there for a reason. Most parts of a pool depend on the coolness of the water, so move slowly and try to avoid doing the work on a day over 85 degrees Fahrenheit. Let's jump in.

1. Consult your manual to ensure there are no recommended steps specific to your pool model before draining.

2. Unplug all electrical features of your pool, including the lighting, pump, and filters. Allow lights to cool down before draining the pool if the bulbs were previously turned on.

3. Connect the hose to your sump pump and extend the hose to the drainage area. 

4. Attach your sump pump to a GFCI outlet and avoid attaching it to an extension cord or non-GFCI plug. 

5. Place the pump underwater in the center of your pool floor and turn it on.

6. Stay with the pump as it begins and check on the flow of the water on occasion. 

7. When the water reaches the height of your pump, turn it off and do not let it pull in air for an extended time.

8. If necessary, use a shop vac to remove the remaining water.

How to Drain an Inground Pool

Draining an inground pool takes a bit more time and patience, but it will be worth it to avoid pool pop. Here's what to do.

1. Just as you did for an above ground pool, disconnect all electrical elements from power such as your pool pump, lighting, automatic timers, and filter. If your lights were previously turned on for a while, let them cool down.

2. Open your backwash valve.

3. If you have one, open the drain to the mainline at the bottom of your pool. The switch is likely in the same area as your backwash valve. Be sure you do not inadvertently open the skimmer drains instead.

4. If you do not have a drain, set up your submersible pump. Attach the hose to the pump and ensure it reaches your desired drainage area.

5. Plug in your pump to a GFCI outlet.

6. Turn on the pump and stay with it during the entire draining period. Double-check that the water properly drains throughout the process.

7. Turn off the sump pump when the water is low enough that it no longer pumps out through the hose.

8. Use a chisel or screwdriver—depending on how it's secured to your pool floor—to open your hydrostatic drains. While groundwater will initially enter the pool, these drains allow the final amount of water to drain.

After you make necessary pool repairs, you will likely need to replace the hydrostatic plugs, as they are often damaged during removal.

Tips to Maintain Your Swimming Pool

Pool maintenance 101 takes time to learn and can seem a bit daunting in the beginning. However, the more you get the hang of it, the more you can avoid large repairs that require you to drain your pool. 

Here are some general tips to avoid major pool repairs:

1. Get to know your pool chemicals and maintain a regular treatment schedule. If you're concerned about this process, set up recurring visits from a local pool cleaner. 

2. Properly close your pool in the winter if you live in an area with freezing temperatures.

3. Update your pool equipment to maintain cleanliness and chemical balances. 

4. Regularly clean out your skimmer, filters, and backwash regularly.

5. Address cracks and holes in your pool liner immediately.

6. Replace your pool filter cartridges every one to two years.

7. Schedule a pool inspection if you are concerned about chemical or structural issues.  

Draining a Pool Yourself vs. Hiring a Pro

Draining a pool falls into the category of common costs of pool repairs. If you prefer to do it yourself instead of hiring a local pool service, the majority of your budget will go toward the price of the sump pump. Buying a pump costs between $100 and $300 on average and between $20 and $50 a day if you rent one. 

Additionally, refilling a pool costs an average of $60 if you do it with a garden hose. A pool drain service will charge $175 to $225, not including the repairs that come after the drainage. However, spending the extra money can ensure that the pool drains correctly and that you avoid pool pop at all costs.