The Inground Pool Pop Up: What It Is, Why It Happens, and How to Prevent It

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 pool 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.

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. 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 floor, which once was solid and smooth, 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 floor up and above the ground. 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!” 

the inground pool pop up, what is it, why it happens and how to prevent it

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.

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 located 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. 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!).

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.

How to Prevent the Inground Pool Pop Up—In Five Steps

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. 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.  

the inground pool pop up, what is it, why it happens and how to prevent 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. 

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. 

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. 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. 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 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.

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.” 

the inground pool pop up, what is it, why it happens and how to prevent it

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.


For additional information on how to get rid of mustard algae, check out this article. Having problems getting rid of white water mold in your pool? Read more here.

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