How to Drain a Pool: The Art and Science of Emptying Your Backyard Oasis

I've drained more pools than I care to count over the years, and let me tell you, there's something oddly satisfying about watching thousands of gallons of water slowly disappear. But there's also something nerve-wracking about it, especially the first time you do it. You're essentially taking this massive container that's been happily holding water for months or years and completely emptying it – and if you do it wrong, you could end up with a cracked shell, a floating pool, or a very angry neighbor whose basement just became an indoor swimming facility.

The decision to drain a pool isn't one you make lightly. Maybe you're staring at water that's turned an alarming shade of green despite your best chemical warfare efforts. Perhaps you're facing a major repair that requires access to the pool's surface. Or maybe you've just bought a house and inherited what can only be described as a primordial soup masquerading as a swimming pool. Whatever your reason, the process demands respect and careful planning.

Understanding Your Pool's Personality

Every pool has its quirks. Concrete pools are the sturdy workhorses – they can handle being empty for extended periods without much fuss. Fiberglass pools, on the other hand, are the divas of the pool world. Leave them empty too long, especially in areas with high water tables, and they might just decide to pop out of the ground like a giant bathtub. I once saw a fiberglass pool that had lifted three feet out of the ground because the owner drained it during the rainy season. It looked like something out of a surrealist painting.

Vinyl liner pools present their own challenges. That liner is essentially a giant plastic bag, and without water pressure holding it in place, it can shrink, wrinkle, or tear. I learned this the hard way when I helped a friend drain his liner pool on a particularly hot July day. By the time we finished, the liner had shrunk so much it looked like a raisin. Expensive lesson learned.

The Great Timing Debate

Timing your pool drainage is like planning a military operation. You need to consider the weather, the water table, and your local regulations. In my experience, late spring or early fall tends to be ideal for most regions. You want to avoid the scorching summer heat that can damage exposed surfaces and the freezing winter temperatures that can cause havoc with empty plumbing lines.

But here's where it gets interesting – and controversial. Some pool professionals will tell you to never fully drain your pool. They'll insist you should only drain it partially, maybe halfway, to avoid structural issues. I respectfully disagree, at least for most residential pools. If you need to resurface, deep clean, or make major repairs, a full drain is often necessary. The key is doing it correctly and quickly.

The Drainage Methods: Choose Your Adventure

The Submersible Pump Method

This is my go-to method for most situations. A good submersible pump can move 3,000 to 5,000 gallons per hour, meaning you can empty an average pool in 8-12 hours. I prefer pumps with at least a 1.5-horsepower motor – anything less and you'll be waiting around like you're watching paint dry underwater.

The beauty of a submersible pump is its simplicity. Drop it in the deepest part of your pool, run the discharge hose to an appropriate drainage area, plug it in, and let physics do its thing. Just make sure you're not that person who drains 20,000 gallons onto their neighbor's property. I've seen friendships end over less.

Using Your Pool's Pump

Some folks swear by using their existing pool pump to drain the water. You can do this by setting your multiport valve to "waste" and essentially reversing the normal flow. It works, but I'm not a huge fan of this method for a complete drain. Pool pumps aren't designed to run dry, and as the water level drops below the skimmer, you risk damaging your pump. If you go this route, watch it like a hawk and be ready to shut it off before it starts sucking air.

The Siphon Method

For the patient among us, there's always the siphon method. It's free, quiet, and surprisingly effective if you have the right setup. You need a significant elevation drop from your pool to the drainage point, and you'll need a long enough hose to maintain the siphon. I once drained a small above-ground pool this way over a weekend. It was like watching grass grow, but it worked.

Where Does All That Water Go?

This is where things get legally murky. Every municipality has different rules about pool water disposal. Some cities are fine with you dumping chlorinated water into the storm drain. Others will fine you into oblivion for the same act. In drought-prone areas like California, you might need a permit just to drain your pool.

The responsible approach – and the one that keeps you out of trouble – is to neutralize your pool water before draining. Let the chlorine levels drop below 0.1 ppm, which usually takes a few days of not adding chemicals. Some people use sodium thiosulfate to speed up the process. Then, ideally, drain to your sewer cleanout or onto a large lawn area where the water can percolate slowly into the ground.

I've seen creative solutions over the years. One neighbor rigged up a system to water his entire landscape with his pool water during a drought. Another pumped it into a tanker truck and donated it to a local construction site for dust control. The point is, there are options beyond just dumping it all into the street.

The Danger Zone: Hydrostatic Pressure

Here's where pool draining can go from routine maintenance to expensive disaster. Hydrostatic pressure – the force exerted by groundwater against your pool shell – is the invisible enemy of empty pools. If the water table in your area is high, that pressure can crack concrete, buckle fiberglass, or even float your entire pool out of the ground.

Most modern pools have hydrostatic relief valves (basically pressure release valves) in the main drain. If you're draining your pool and water starts bubbling up through these valves, stop immediately. That's groundwater trying to equalize pressure, and it's telling you that draining further could be catastrophic.

I always recommend checking the weather forecast for the week before and after you plan to drain. Heavy rain can raise the water table quickly, turning a routine drain into a potential disaster. In Florida, where I spent a few years, pool professionals wouldn't even consider draining a pool during hurricane season. The water table there can be just a few feet below ground level.

The Cleaning Window

Once your pool is empty, you're on the clock. Concrete pools can start developing surface cracks from thermal expansion and contraction within days. Plaster can delaminate. Vinyl liners can shrink. This isn't the time to take a vacation.

I like to have all my cleaning supplies and repair materials ready before I even start draining. Power washer? Check. Acid wash supplies? Check. Patch materials? Check. The goal is to get in, do what you need to do, and start refilling as quickly as possible.

One trick I've learned: if you're acid washing, work in sections and rinse immediately. Don't let the acid sit on the surface while you go grab a sandwich. I watched a DIYer essentially etch modern art into his pool surface by letting muriatic acid sit too long. His pool looked like a Jackson Pollock painting, but not in a good way.

The Refill: More Than Just Turning On the Hose

Refilling seems simple enough – turn on the water and wait. But there's an art to it. Start slowly, especially with vinyl liner pools. You want the liner to settle gradually into place. With concrete pools, I like to brush the surfaces as they're covered with fresh water to prevent any dust or debris from settling and staining.

Keep an eye on your water meter during the refill. A typical residential pool holds 15,000 to 30,000 gallons. At standard household water pressure, you're looking at 12-24 hours of continuous filling. Some water companies will give you a credit on your sewer bill if you tell them you're filling a pool, since that water isn't going into the sewer system.

The Hidden Costs Nobody Mentions

Let's talk money, because draining and refilling a pool isn't cheap. The water alone can cost anywhere from $100 to $500 depending on your local rates and pool size. If you're hiring professionals, add another $500-$1,500 for the drain and clean service. Throw in chemicals to rebalance your fresh water, and you're looking at a significant expense.

But the real hidden cost is what happens if something goes wrong. A popped fiberglass pool can cost $10,000 or more to reset. A severely cracked concrete shell might mean a complete renovation. This is why I always recommend having a professional assess your specific situation, especially if you've never drained your pool before or if you live in an area with known high water tables.

My Final Thoughts

After all these years of working with pools, I've come to see draining as a necessary evil – something you do when you must, not just because you feel like it. The old-timers who built pools in the 1960s and '70s used to say, "A pool wants to be full," and they weren't wrong. These structures are designed to hold water, to push back against the earth with the weight of thousands of gallons.

But sometimes a drain is unavoidable, and when that time comes, approach it with the respect it deserves. Plan carefully, work quickly, and always have a backup plan. Because at the end of the day, a pool is a hole in the ground that desperately wants to be filled with something – preferably water, but it'll settle for dirt if you give it the chance.

The satisfaction of refilling a freshly cleaned pool, watching that crystal-clear water slowly rise, knowing you've done the job right – that makes all the stress worthwhile. Just maybe wait a while before you need to do it again.

Authoritative Sources:

Association of Pool & Spa Professionals. The Complete Guide to Pool Care. APSP Press, 2018.

Tamminen, Terry. The Ultimate Guide to Pool Maintenance. 3rd ed., McGraw-Hill, 2007.

United States Environmental Protection Agency. "Swimming Pool Discharges." EPA.gov, Environmental Protection Agency, 2021.

Wood, Robert W. Pool and Spa Operator Handbook. National Swimming Pool Foundation, 2019.