Big sigh. There comes a time in any pool owner’s tenure that they realize that they’re going to need to pull the plug on their pool—but only a short time before filling it back up. Draining your inground pool usually only needs to happen every few years, but it is an inevitable part of swimming pools maintenance. And not only does it take a full working day of overseeing the process, but it can also be a tense moment: thanks to one catastrophic event that happens to the most unlucky of us once the pool is mostly drained.
This event is known as pool popping (also called popping), and it can affect various types of swimming pools, including concrete, gunite, and fiberglass pools. Because these pools are constructed as a vessel set into the ground, they are susceptible to ground water pressure that can cause the entire pool shell to shift, crack, or even lift out of the ground if not properly managed.
I present to you your worst nightmare: the inground pool pop up. The good news is that it doesn’t take much extra work to prevent it from happening—and save your pool from destruction. The phenomenon of pool popping is not limited to one type of pool material; both concrete and fiberglass pools, as well as gunite pools, can experience this issue if the conditions are right. I’ll explain what the pool pop up is, why and when it happens, how to know if you’re at a higher risk, and how to prevent the pool pop up from happening—in five easy steps.
Wait a Minute. What is the Pool Pop Up?
We’re about to enter a Hollywood-level scene here, but unfortunately this scenario does happen in the real world. Imagine that you’re draining your pool for any reason—whether that be to reset your water chemistry because your total dissolved solids (TDS) are through the roof and preventing your sanitizer from working, or because your pool floor needs some painting or plastering, or because you’ve got pesky metal stains you want gone once and for all. But once your water is gone, something goes terribly wrong. Your pool shell, which once was solid and smooth, can lift, float, or even be popped out of the ground due to hydrostatic pressure, sometimes resulting in cracks or cracking of the structure. Your pool floor pushes up from out of the ground—and breaks into bits as it does. Now you’ve got a shallow end and a pile of rubble where a deep end was.
That, my friend, is the inground pool pop up. Without thousands of gallons of heavy pool water weighing down the pool floor, the pressure from around your pool could push your pool shell up and above the ground. When pool pops occur, the shell is often cracked or displaced, and the pool may be left in a severely damaged state. And that last thing you want is for it to happen to you.
Restoring your chemical balance is all the easier with a powerful pump. If a larger horsepower will turn over your water volume at a sufficient rate—and won’t overwhelm your filtration system—then a unit like this Blue Torrent 2 HP Variable-Speed Pump is the one to try. As customer Dave Schmidt says, “My pool has never looked cleaner. I am pleased with my new pump!”
You Might Be More Susceptible—Without Even Knowing It
Not to take you back to the awkward days of middle school, but there was something in that one geological science class that is relevant to your home now. You might remember a chart mapping out what is happening under the earth’s surface: first is the soil zone, and then below it is something called a water table, which is the main culprit here. It’s exactly what it sounds like: a water table is the layer of ground underneath us that is saturated with water. And if yours is high, you are all the more likely to experience the dreaded pool pop up. Ground water outside the pool can exert significant pressure on the pool shell, and when the pressure outside becomes equal to the pressure inside the pool, the risk of your ground pool popping out increases.
No matter where you live, you have a water table—and it hardly stays in one place, depending on the time of year. During the late winter and spring, when snow (if you have it) begins to melt and you get that nice, consistent spring rain, water sinks into your soil and your water table rises. Since spring plants react to the moisture and start to suck up the water, and summers are usually more dry, you can expect the water table to fall during the summer—unless you live somewhere that gets serious monsoons.
You can find information about recorded water tables in your area through the U.S. Geological Survey’s National Water Information System (NWIS), which has measurements made in the present and past, and The National Groundwater Monitoring Network, which is a compilation of groundwater monitoring from federal, state, and local groundwater networks across the nation. Water table depth and water level data are monitored across the country, and these measurements are important for all types of ground pools to assess ground water conditions and potential risks. This should give you a good sense of whether you have a high water table—and if you do, you’re going to want to be extra careful when choosing when to drain your pool.
When Does the Pool Pop Up Happen?
Thankfully, the pool pop up rarely happens. In fact, it’s an extremely rare occurrence, and it usually happens when there’s a major flooding event or hurricane in the area, which saturates the ground and creates a super high water table. It probably won’t happen to you, but it’s the type of disaster you’ll want to avoid at all costs—because if it does happen, it is going to cost you more than either of us want to imagine.
When it does happen, it’s usually when the presence of water in the ground under and around your pool increases the pressure. This pressure is ultimately what pushes your pool floor up and out of the ground—and wreaks havoc on your pool (and your life!). In many cases, extensive repairs are required to address the damage, and the pool shell may need to be repaired or even replaced. Consulting a professional contractor is often the best option to assess your specific case, discuss available options for repairs or replacement, and ensure the work is done correctly. Contractors have experience handling these cases and can provide guidance on the best course of action.
If you’re fixing your pool’s liner or doing any other maintenance, and need a completely dry floor to work, use a heavy-duty and durable cover pump like the BLACK+DECKER 1500 GPH Automatic Submersible Pump. It works on its own to detect water up to 1/8 inch and comes with a whopping 30 ft discharge hose and 25 ft power cord.
I think we’re on the same page here—the pool pop up is not something we want on our list of expenses, and it’s worth taking some precautions to ensure it’s not on our list of grievances. Take these five simple and easy measures, and you’ll be glad you did.
1. Wait for a Sunny Week—Or Longer
Had a few days of heavy rain? Yeah, this is not the time to start draining your pool. Whatever task you had planned can wait—and it’s going to have to go to the back burner while your weather calms down and your ground dries up. It is a common mistake to drain the pool too soon after rain; it is recommended to wait until the ground is thoroughly dry before proceeding. Remember, what we’re worried about is rain collecting well under the surface of your soil. Even if it’s sunken as far down as your deep end, and that’s often an upwards of eight feet, we’ll still have a pressure problem. Don’t be fooled into draining your pool the second your ground looks dry on the surface—you might seriously regret it.
2. Get a Drain Game Plan
Alright, so you waited for a long, dry season to drain your pool. That’s great. But there is still a potential to blow it, and it all lies in your game plan.
When you drain a pool, you displace thousands of gallons of water—and it’s all got to go somewhere. Make sure you check with your local water authority, since they tend to have an opinion about the chemical potency of your water, and where it should be disposed. Draining an inground pool is already stressful, and you don’t want to also get slapped with environmental fees.
Proper attention to your pool's plumbing is essential during the draining process. Certain components, such as hydrostatic relief plugs, should be removed at the right time and not left unattended after draining, as leaving the pool empty for too long can lead to issues caused by hydrostatic pressure. The most important part of your draining process, other than finding the right disposal place, is making sure that your water actually ends up where you’ve planned. I probably don’t need to say this, but make sure that your drainage hose is long enough before you start the draining process. If it comes up short, those thousands of gallons of water could go straight into your yard around your pool—and that’s just asking for the pool pop up to happen.
If you are unsure about which steps to take during the draining process, I suggest consulting a pool professional to ensure everything is done safely and correctly.
3. It's All Downhill from Here
This is also part of your drainage game plan, but it's important to highlight on its own—it's a trick that a lot of pool owners overlook when draining theirs. Wherever your drainage location, make sure that it's downhill from your pool. This means that if there are any accidents, your water is less likely to saturate the area around your pool.
One common issue can occur when you drain into your sewer system: you hit a clog. It's not often that homeowners discover a clog in their system until they're pushing thousands of gallons of water through—and if that water hits a clog, it's going to come right back at you. Draining downhill will mitigate that damage.
Now that your pool is getting drained, are you noticing that it's a lot filthier than you thought? It's time to give your automatic cleaner a much-needed upgrade by switching to the Blue Torrent MyBot Inground Robotic Cleaner, which works powerfully on its own to keep your walls and floor sparkling clean. As customer David Lain says, “Very pleased. My wife loves it.”
4. Release Your Relief Valves
Believe it or not, your pool actually has built-in protectors against the pop up nightmare: hydrostatic pressure relief valves. I know, they have a pretty intimidating name. But they’re on your team here.
When you look at your pool, you’ll see one or more white rings embedded in the floor. These valves are typically located at the deepest point of the pool, which is the most vulnerable area for pressure buildup. Under that, they’re threaded into a slotted pipe, which runs along the floor of the pool and connects to a gravel pit underground.
These little guys are important because, unseen to us, there might be water that has accumulated under your pool. In the case of high ground water pressure, it is correct to open the relief valve to prevent damage. If this water under the pool doesn’t have the weight of water in your pool to keep it down, the pressure will cause your pool floor to pop up. Pull these valves, and the water under your pool will come up into your pool, the pressure will be relieved, and you’re even further from any possibility of the pool pop up.
So how can you open these valves? Well, first wait for the right time: you only want to open them when the pool is mostly drained. When your pool is ready, just use a hammer and chisel to break and remove the plaster inside the valve cap. Once you do that, you’ll see a threaded plug. Use pliers to turn that plug counterclockwise and it’ll come right up, and you’ll probably see water come up into the pool immediately. When you’re ready to refill the pool, replace the valves with either a new valve plug or the old one, depending on how hard you used that chisel to get it off. To prevent leaking, put Teflon tape on the threads before twisting them into place.
5. Fill ‘er Up—ASAP
This goes beyond just your pool pop up—which can happen if you leave your pool drained for a long time. (And this shouldn’t need to be said, but don’t be the person who leaves their pool drained in the rain!) But leaving your pool drained for longer than is absolutely necessary can also damage your liner. An empty pool is at greater risk of structural damage due to ground water pressure and buoyancy, which can cause the pool to lift out of the ground. An inground pool is meant to be filled with water, not hot sun and air. Restore equilibrium as soon as possible to dodge any other costly damage coming your way, and continue monitoring your pool during the filling process to ensure everything remains safe.
Reminder that as of 2021, the switch to variable-speed pumps will virtually be federal law. Thankfully, the Blue Torrent 2 HP Variable-Speed Pump is ultra-powerful, comes with a lifetime warranty, eligible for rebates, and pays itself off in under a year by energy saved. As customer Bill Britton says, “Runs great. Super quiet.”
Well, That Was Draining—But Not Catastrophic!
As with all routine maintenance, including closing your inground pool for the season, the extra effort you've just made far outweighs the work necessary to recover later, this time from the inground pop up. And a mean, by a lot. You made sure you drained properly, chose the right time to do it, and pulled a few valves. That's a lot better than replumbing and rebuilding the bottom of your pool, not to mention any other damage to your yard or overall system that might have occurred. But that likelihood doesn't apply here anymore: now you can cross the inground pool pop up right off your list of worries. And once you refill your pool and restore it back to normal, you can breathe a major sigh of relief—preferably while floating on your back in your clean, intact pool. Enjoy.
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