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

Swimming pools sit like small captured oceans in our backyards, holding thousands of gallons of chemically balanced water that, at some point, must be released back into the world. Whether you're facing a green swamp after a neglected summer, preparing for major repairs, or simply need to start fresh with your water chemistry, draining a pool becomes an inevitable task that many homeowners approach with equal parts determination and dread.

I've watched countless pool owners stand at the edge of their concrete-lined water features, garden hose in hand, wondering if they're about to make an expensive mistake. The truth is, draining a pool incorrectly can lead to catastrophic damage – from popped pools that literally lift out of the ground to cracked plaster that turns your smooth swimming surface into something resembling the moon's cratered face. Yet when done properly, it's a straightforward process that any reasonably handy person can tackle.

Understanding Your Pool's Personality

Every pool has its own quirks and characteristics. Fiberglass pools, for instance, are particularly temperamental when empty – they're like boats that prefer to float rather than sit dry. The groundwater pressure beneath them can actually push them upward if you're not careful, especially after heavy rains. I once saw a neighbor's fiberglass pool rise three feet out of the ground because they drained it during Florida's rainy season. It looked like a giant bathtub trying to escape.

Concrete and gunite pools are more forgiving but come with their own set of concerns. The plaster finish can crack and separate if left dry too long in hot weather. Think of it like leaving a clay pot in the desert sun – eventually, it's going to develop stress fractures. Vinyl liner pools present yet another challenge: the liner can shrink, wrinkle, or tear if not handled correctly during the draining process.

The Pre-Drain Checklist

Before you even think about where to put all that water, you need to check with your local municipality. Many areas have strict regulations about where pool water can be discharged, especially if it contains high levels of chlorine or other chemicals. Some cities require you to neutralize the water first or direct it into the sanitary sewer system rather than storm drains.

I learned this lesson the hard way when I first moved to California during the drought years. My neighbor called the city on me when I started draining directly into the street gutter. The fine was... educational. Now I always call the local water authority first – they're usually helpful and can save you from making costly mistakes.

Weather plays a crucial role too. Never drain a pool when rain is expected within the next few days. Groundwater levels rise during storms, and that external pressure can wreak havoc on an empty pool. Similarly, extreme heat can cause plaster to crack, so if you're in Phoenix in July, maybe wait for October.

The Drainage Methods: Choose Your Adventure

The Submersible Pump Method

This is my go-to approach for most situations. A good submersible pump can empty a 20,000-gallon pool in about 8-10 hours. You'll want one that can handle at least 3,000 gallons per hour – anything less and you'll be waiting around like you're watching paint dry in slow motion.

Place the pump at the deepest point of your pool. I usually put mine on a milk crate or similar platform to keep it slightly elevated from the very bottom – this prevents it from sucking up too much debris in the final stages. Run your discharge hose to wherever your local authorities have blessed as an appropriate dumping ground. For many folks, this means connecting to a sewer cleanout in your yard.

One trick I've picked up over the years: use a timer on your pump if you're draining overnight. Calculate roughly when your pool should be empty and set the timer to shut off an hour before that. This prevents the pump from running dry, which can damage it, and gives you a buffer in case your calculations were off.

The Pool Pump Method

Your existing pool pump can also do the job, though it's generally slower and requires more babysitting. Set your filter to "waste" or "drain" mode – this bypasses the filter and sends water directly out through your backwash line. The advantage here is that you're using equipment you already own. The downside? You need to monitor the water level constantly because once it drops below the skimmer, you risk burning out your pump motor.

Some pool owners get creative and remove the drain plug from their filter system, but I've seen this go wrong more times than I care to remember. One friend forgot about the open drain plug when refilling and wondered why his pool wouldn't hold water for three days. We don't talk about how much water he wasted.

The Siphon Method (For the Patient Soul)

If you're not in a hurry and want to save on electricity, you can siphon your pool using nothing but a long hose and gravity. This method works best if you have a lower area where you can discharge the water – maybe a slope in your yard or a drainage ditch. It's slow, taking several days for an average pool, but it's free and requires no equipment beyond a garden hose.

To start a siphon, you'll need to fill the entire hose with water first. I usually connect it to a faucet, run water through until it comes out the other end, then quickly disconnect and plunge the input end into the pool while keeping the output end lower than the water level. Physics does the rest, though you might need to repeat the process if air gets into the line.

The Danger Zone: When to Stop

Here's where many pool owners make their biggest mistake. You should never completely drain a pool unless absolutely necessary. Leaving 6-12 inches of water in the bottom provides weight to counteract groundwater pressure and helps prevent damage to the pool structure.

For vinyl liner pools, I recommend stopping when there's about a foot of water left. This keeps the liner from pulling away from the walls and potentially tearing. You can use a regular sump pump or even a shop vac to remove the remaining water if needed for repairs.

Fiberglass pools are the most sensitive. In areas with high water tables, you might need to simultaneously pump groundwater from around the pool shell while draining the pool itself. Some installers put in hydrostatic relief valves for this purpose – they look like little plastic plugs in the pool floor. If your pool has these, make sure they're working before you drain.

The Refill: Bringing Your Pool Back to Life

Refilling seems simple enough – turn on the hose and wait, right? Well, yes and no. The key is to refill as quickly as possible to minimize the time your pool sits empty. I usually run two or three hoses if possible. Garden hoses typically flow at 5-10 gallons per minute, so do the math on how long you'll be standing there.

Place the hose in the deep end and let it run. Some people worry about disturbing new plaster, but modern plaster is pretty tough. I do recommend putting the hose on a rag or towel to prevent it from leaving marks on the pool floor as it whips around.

Watch for leaks as you refill. Sometimes the pressure of draining and refilling can reveal problems that were hidden before. I once discovered a hairline crack in my skimmer that only showed itself during the refill process. Better to catch these issues early than wonder why your water level keeps dropping later.

The Chemistry Reset

Fresh water means starting from scratch with your pool chemistry. Your tap water might be very different from what you drained out. Test for pH, alkalinity, calcium hardness, and stabilizer levels. You'll likely need to add quite a bit of chemicals to get everything balanced.

Don't add all your chemicals at once. I learned this lesson when I dumped in what I thought was the right amount of everything, only to create a cloudy mess that took a week to clear. Add alkalinity increaser first, then pH adjuster, then calcium if needed. Wait a few hours between each addition and test frequently.

One often-overlooked step: if you have a salt water system, you'll need to add all new salt. Figure on about 50 pounds per 2,000 gallons of water to reach the typical 3,000-3,500 ppm level most salt systems require. Add it gradually while the pump is running and brush it around to help it dissolve.

Special Circumstances and Warnings

If you're draining for repairs, timing is everything. Plaster work, tile replacement, or crack repairs all have their own schedules. Coordinate with your contractors so the pool isn't sitting empty longer than necessary. I've seen too many pools damaged because the homeowner drained two weeks before the repair crew could arrive.

Winter draining is its own beast. In freeze-prone areas, you might need to drain below the skimmer and return lines to prevent freeze damage. But don't drain completely – that winter groundwater is often higher than summer levels. Many pool professionals in cold climates recommend using air compressors to blow out lines rather than draining significantly.

Never, and I mean never, drain a pool to solve an algae problem. I know it's tempting when you're staring at something that looks like pea soup, but algae can be killed and filtered out. Draining should be a last resort for water chemistry issues, not a first response. The only exception might be if you have extremely high stabilizer levels (over 100 ppm) that can't be diluted effectively.

The Hidden Costs Nobody Mentions

Let's talk money for a moment. Draining and refilling a 20,000-gallon pool costs more than just your water bill. In my area, water runs about $3-4 per thousand gallons, so that's $60-80 right there. Add in chemicals to rebalance everything (another $100-150), electricity for pumps, and potentially a day off work to supervise, and you're looking at a $200-300 project minimum.

If you hire professionals, expect to pay $500-800 for a drain and refill service. They'll handle the permits, have commercial-grade pumps, and know exactly how to avoid damage. For many people, especially those with expensive pools or high water tables, this is money well spent.

Final Thoughts from the Deep End

After draining dozens of pools over the years – my own and those of friends who've enlisted my help – I've come to see it as a necessary ritual of pool ownership rather than a dreaded chore. There's something satisfying about seeing your pool's true surface, addressing any issues, and starting fresh with crystal-clear water.

The process demands respect but not fear. Take your time, follow local regulations, and don't cut corners to save a few hours or dollars. Your pool is likely one of the most expensive features of your home – treat it accordingly.

Remember that every pool is different, every situation unique. What works for my gunite pool in Southern California might not work for your vinyl liner pool in Ohio. When in doubt, consult with local pool professionals who understand your specific conditions and challenges.

The most important advice I can give? Don't drain your pool on a whim. Have a plan, have a reason, and have a backup plan if things go sideways. Because while pools are designed to hold water, they're surprisingly vulnerable when empty – like fish out of water, they're outside their natural element and need careful handling to survive the experience intact.

Authoritative Sources:

Association of Pool & Spa Professionals. The Ultimate Pool Maintenance Manual. McGraw-Hill Education, 2018.

Tamminen, Terry. The Ultimate Guide to Pool Maintenance. McGraw-Hill Education, 2007.

U.S. Environmental Protection Agency. "WaterSense: Outdoor Water Use in the United States." EPA.gov, 2017.

Wood, Robert W. Pool and Spa Operator Handbook. National Swimming Pool Foundation, 2016.

California Department of Water Resources. "Model Water Efficient Landscape Ordinance." Water.CA.gov, 2015.