"> Help! There is something sharp under my pool liner – Above Ground Pools Know it All

Help! There is something sharp under my pool liner

Above ground swimming pools are pretty awesome. They can go up in a day, fill up with water in another. Then you can be swimming a day after that.

Most above grounds have earth bottoms. This is ok except when you are swimming along and discover something sharp at the bottom and under the liner. Yikes!

Having something sharp under your above ground pool liner is usually not a big deal. It can be easily fixed by taking a piece of wood and hammering down the object. Place the wood over the sharp object and use the hammer to gently tap the object down. If the object tapped down flat and you no longer feel it, check to make sure the tapping didn’t make a hole (it rarely does). If no hole, then you are done. It’s fixed and will not come back up.


In thirty-six years of installing above ground pools, I’ve seen a lot of weird things under a pool liner including a close-pin that I left behind during my install (that was several years ago when I used close pins to keep the liner in place). Here are the more common items:


Rocks come in all shapes and sizes. Some are smooth, some are jagged. Some are small pieces of concrete and some are pieces of crushed shell. The sharp-edged and jagged rocks are obviously more concerning than the decorative, smooth stones.

Most earth will have at least a few rocks in it. Some sand you buy will have a couple of rocks. Rocks are common in the earth. Don’t stress too hard if you feel one or two under the liner.


Roots can be a little more concerning than rocks, but they are usually no big deal either. It is very common for a pool site to have some existing roots in the earth. I have built pools that were completely out in the open and a hundred yards from any tree. There were roots in the earth.

A small root piece that was just missed under the liner is not a big deal. Where it becomes a big deal is if that root is still connected to the root system. This means that the root that you feel under the liner may not move. Because it’s still connected to other roots.

In all the years that I have had to fix sharp things under pool liners, I have only had to drain the pool to fix the issue twice. Both times were when there was a root that was still attached. This is not good.


Interestingly, there’s not as much glass in the earth as there was. I’ve been putting above ground pools in the ground for more than three decades and recently recalled most pool sites having some amount of pieces of glass.

My guess is that since we, as a society, have replaced many things that were made of glass now with plastic. This has resulted in less glass in the earth.

There is still some glass to be found in the earth though and although there is much less than before, one or two pieces is still fairly common.

Glass under the pool liner usually sounds worse than it actually is. Most glass pieces in the earth aren’t very sharp anymore as the broken edges will dull over time.


Don’t know what nutgrass is? Have you ever seen grass growing through a black asphalt road? That’s nutgrass. It is one of only three things that I have ever seen grow right through a liner. The two other things were one time occurrences.

Nutgrass or Nut Sedge is a very common problem with above ground pools. Before it punctures the liner and starts growing through, it makes a very sharp edge against the liner.

When people feel this, they usually think it’s something else. Then this perfect blade of grass pokes through and then they know. Learn how to prevent nutgrass from growing in your pool here.

Old construction trash

Back in the early nineties and before, when a house got built, they used to bury whatever trash there was from the construction of the home. This has long since been outlawed but you’d be surprised at how much construction-related trash there still is in the ground of back yards.

I have frequently found items like nails, tile pieces, shingle pieces, concrete, metal trim, wood, and beer cans that were all related to the construction of the home (or a later addition). This can be a pain and some things can get left under the liner.

A screw from the pool install

Well, this happens even to the best of us. A screw will fall into the bottom of the pool right before the liner goes in and no one will notice.

In an oval – part of the pool’s structure

Unlike the much simpler round-shaped above ground pools, oval pools have metal parts that run underneath the pool’s bottom. Sometimes, these metal parts can find their way close enough to the surface of the bottom of the pool to be felt. This is not good but usually will not cause a hole in the liner.

Some oval designs are not great and so are prone to this happening. It’s rarely the end of the world and the pool owner usually just lives with it. To fix it though, the pool almost always has to be drained.

Horned nose beetle

Although rare, horned nose beetles can make a hole in an above ground pool liner. Most of the time, this is mistaken for a rock.

Many years ago, I was installing pools for one of those companies that sell above ground pools for twenty thousand dollars if they can. They suck but I didn’t know about them at the time. Just that they paid me a few hundred more than my price.

Anyway, I had this one pool owner all bent out of shape because he could feel a rock under his liner and it was obviously the installer’s fault (mine). Now, this guy was indignant and I was much younger (in my early twenties), so I put up with his unnecessary abuse.

I went out to his house and had to field his abuse as I got into the pool to investigate the rock under the liner. After bitterly pointing out the area of the pool where the rock was, he waited as I went under the water. When I broke the surface, I had a horned nose beetle in my hand.

“This wasn’t a rock. It was this. A horned nose beetle” I told him. “I didn’t leave anything under your liner, this guy crawled under the liner afterward. And it’s not covered under any warranty” (Learn more about liner warranties)

It took a couple of minutes for this angry guy to process the false, negative conclusion he made of me and I greatly enjoyed is lack of ability to apologize to me.


You may only need the first two items, but for the sake of being thorough, I’ll list everything.

  1. Hammer
  2. Small piece of wood
  3. Diver’s weight belt or something heavy to easily keep you under the water
  4. Sharp utility knife
  5. Underwater vinyl patch kit
  6. Quarter
  7. Syringe needle (or any applicator) with round-up in it (for nutgrass repair only)


  1. Weigh yourself down with something so you can stay at the bottom of the pool without floating up.
  2. If you don’t know what it is, take a small piece of wood and a hammer down to where the sharp object is.
  3. Place the wood over the sharp object and use the hammer to gently tap the object down
  4. If the object tapped down flat and you no longer feel it, check to make sure the tapping didn’t make a hole(it rarely does) If no hole, then you are done. It’s fixed and will not come back up.
  5. If your tapping made a small hole, no big deal at all. Use the quarter to cut a circle patch from the repair kit and follow the directions to gluing it on the hole. Now, you are done.
  6. If the object does NOT TAP DOWN, then try to determine what it is.
  7. If you think it’s just a rock or some unattached piece of construction trash or a beetle, then you can take the utility knife and make a small cut so you can pull the object out. NOTE: I don’t usually recommend cutting a hole in the liner. If there is already a hole, then you don’t have as much to lose.
  8. If you successfully removed the sharp object from the hole you made, then great. Patch the hole and you are done.
  9. If the object did not tap down and/or you have determined that it’s an attached root, then you can either live with it or you’ll have to drain the pool all the way down, peel the liner back, dig up and remove the root, replace the liner and refill the pool. Note: This is a rare option. If you must do this, keep in mind that the liner will begin to shrink as soon as you drain the pool. Make this repair within minutes of draining the pool and get water back in it ASAP!
  10. If the object is nutgrass, pull the blade of grass out from the hole, inject some roundup into the hole (to kill the remaining nutgrass), then patch the hole with the underwater patch kit, and you are done.
  11. When/If you have determined that the sharp object is part of the pool’s structure (ovals only), call the guy who installed the pool and have him look at it. If you built the oval, decide if the area is sharp enough to make a hole. If it is, you may have to drain the pool and cover the area with more earth or sand. Note: Due to some poor designs, some oval pools will lift a bit and expose some of the water plates or straps that run underneath the pool. This usually doesn’t have to be repaired as those parts you see and feel will still have a layer of earth or sand between them and the liner.

While I’ll admit it sucks to discover something sharp under your above ground swimming pool liner, in most cases, it’s no big deal.

One of the things that I like about above ground pools is that they can have a more natural feel to then than a concrete or fiberglass pool. This is mainly because most of them have an earth bottom with nothing between your feet and the planet except a liner.

There are some drawbacks to this though. The earth is alive and dynamic, so sometimes things are going to happen. Fortunately, most things that happen are easily fixed.


Dan writes with the knowledge of having 35 years (and counting) in the above ground pool industry.

28 thoughts on “Help! There is something sharp under my pool liner

  1. Hello, I assembled my Coleman above ground pool myself. After assembling and filling with water I noticed I missed a brick that was stuck underneath. It’s taken two days to fill the pool so I really don’t want to drain it. Will the wood and hammer work for that?

  2. Dan, I need to write to you and say thank you a million times. Long story short I had a pool installation nightmare and it was one mess up after another. The last straw was three sharp (felt like nails or rock) poking through my above ground liner. I didn’t want that company coming back out so in desperation I found your post/ blog. It worked like a charm. Couple taps of a 2×4 on the sharp points and they are gone. My hero. If I live near you….. you would drink for free as long as I could help it. Many thanks.

    1. Wow!! Very glad this was helpful. I’m not a big drinker, but I wouldn’t turn down a shot of Casamigos reposado.

  3. Good article! I do have a question that perhaps you can help with. We have a new above ground pool this summer. There are two places where heavy rains washed out the sand “cove” where the metal wall meets the ground. This left two low spots on the pool bottom, and about 6 inches up the wall there are some rocks stuck. One has already caused a small leak.

    I’m not too worried about the low spots, they just collect dirt. But the rocks are already causing problems. Is there a way to get them out? Can I slide my hand up from the bottom some how? Or should I cut the rocks out?

    It’s a little hard to explain, hopefully that all makes sense.

    1. Thank you. It’s not at all likely that “heavy rain” washed out your coving. Water has to move earth for errosion, so only rain cannot do that. More than likely, a hole in the liner caused the coving to wash away.

      If you have rocks stuck 6 inches up the wall, there is really no way to remove them without either draining the pool or cutting them out and patching where you made the cuts. I don’t advise either. I would leave the rocks and do a dye test to make sure there are no holes in the liner in that area. If I find a leak, I would simply patch it (even if it’s directly over a rock.

      These trapped rocks against the pool wall(which is a rare occurrence) is an annoyance, but shouldn’t cause any issues if kept there. When the time comes to change the liner, you can then remove them.

  4. Hello, Just a little annoyed.. I had a pool installed 2 weeks ago. I feel sharp objects under the liner in 2 separate places. I’m afraid it’s going to put a hole in the liner. Should the company be responsible for fixing it? I paid a lot of money for this pool with the installation. However, I don’t want to drain in it took over 2 days to fill. What can I do or expect them to do?

    1. What makes you think it has to be drained? It usually can be corrected without draining. If you aren’t happy with the bottom of the pool, then yes, the installer should at least come out and investigate the sharp spots. The issues may or may not be their fault. As a pool installer, I would need to and want to check it out to see what it is. Having the installer come out to investigate is not too much to ask.

  5. I recently put in a 21×41 doughboy…on the day of install it rained on and off…I watched them smoothing out the bottom for a bit and went back inside …all of a sudden it was going to rain hard…they had the liner in and were filling. We have alot of baseball size indents and the bottom feels very rough…is the roughness normal? How rough is ok…I don’t want the liner going bad ! Thanks!

    1. A bottom can be very rough and bumpy without there being any issues. It’s just annoying when vacuuming and walking in the pool when the bottom isn’t very smooth. The liner will last just as long though.

  6. We have a brick that migrated from under the support wall and the corner of the brick is almost poking thru the liner. We are going to have the installers drain, pull the liner back and push the brick back, but we’re wondering if there is any risk in waiting until spring to do it? Is there anything to consider about freezing temps and the brick pressing against the liner? We don’t want to drain the pool to fix the brick and fill it back up to adjust the levels and winterize, then half drain it again right away for winter. Hoping we can wait to do it all in the spring.

    1. Ok so first off, the brick can’t move on it’s own so it didn’t migrate. Most likely there wasn’t enough earth/sand that was suppose to cover it or something displaced the earth/sand(very uncommon). Most likely there is a layer of earth/sand between the liner and the brick which is good. I have made this kind of repair without draining the pool, but that may be a lot to ask the installer if he doesn’t have enough experience. Plus it doesn’t come out perfect.

      What I don’t know for sure is if the freezing temps will affect this. I’m thinking not though. My best guess is that you can wait.

  7. We just had our pool put up. We have two low spots along the edge where the cove should be. One spot where the screws run down the pool. I don’t feel anything sharp there, so I feel that should be okay? The other spot I’m more concerned about. It is where a upright is and you can feel the edge of the upright base pressing into the liner. Is this something that could cause a hole? Is there anyway to get it not to press into liner other than draining the pool and fixing the cove?

    1. If you are feeling the patio stone used to level the pool(from under each upright), then that is better than if you are feeling the bottom connector. If you are feeling the bottom connector, then that would mean you don’t have a coving in that area which is not good.

      If just feeling the patio stone, I would say it’s worth correcting but there’s probably a thin layer of earth between it and the liner which will prevent it from easily getting torn/a hole.

      There is a fix without having to drain the pool, but it would take someone with a lot of experience to do that AND it wouldn’t feel perfect. You’re most likely better off draining and correcting.

  8. Thank you for your help. It is the connector part that I am feeling. Hope the company will be easy to work with and pay to fix there mistake. So is the connector a pretty high chance of tearing the liner? Any other big issues to worry about with it being the connector?

  9. Dan, you are a genius!!! I lost actual sleep last night at the thought of having to auger under our above ground pool, drain it, or intentionally cut a hole in the liner then patch it before reading your idea about using a wood plank and hammer to tamp it down!!! I was linked to your website from another website. I had to chuckle bc it was clear folks were confused at THAT poster’s description of swinging a hammer under water using a small square of wood. Using a 5 foot long 2×4 plank of wood and swinging the hammer while above the surface of the water had this otherwise nightmarish project done and over in less than 5 minutes! I was happily searching for other roots to tamp down! Thank you so much for sharing your knowledge online! Wishing you many years ahead of good health and happiness!

  10. I found a wood block under neath my liner :/ pretty sure it has poked a hole in the liner, any recommendations? It’s about a foot from the pool edge and would like to avoid draining it. Any help would be appreciated

    1. It’s not likely that a piece of wood can make a hole in the liner. But if you have a hole above a piece of wood under the liner, then you can follow the instructions in the article and patch the liner. Just make sure it’s not a support that was placed under you uprights. Usually, patio stones are used for this but I’ve seen wood used.

  11. We recently put up a 48” by 18 feet pool. We used concrete pavers under each leg to prohibit the legs sinking into the earth. We filled our pool and jumped in it today. I noticed that some of the pavers were pushed to close to the liner and the sharp edge is pushing into the liner. Is this something that will cause a tear to happen eventually? We also have a layer of tarp buffering between it but it feels like the sharp corner edges are cutting into it. Are we going to have to drain our pool?

    1. I’m thinking that you have a soft-sided pool. With those, you can carefully dig out the paver/s in question(one at a time) and set them a little lower in the ground. This should enable you to pack some dirt between the liner(and that cheap tarp) and the paver.

  12. I have a 27 foot above ground pool and tonight I found something pushing against the liner in the corner. When I do down and touch it with my hand, it feels sharp. I assume if it keeps moving it will create a tear. If I use the wood and tap method you mentioned, do you think I should also put a patch in that spot?

    1. It will usually just go down and not need a patch. Since I don’t know how sharp it is, I recommend you having a underwater patch kit ready to be used just in case tapping it down causes a hole.

  13. Thank you!!!! We live on top of a hill, and you find shale even just sitting on top of the ground sometimes. We were freaking out, walking our pool as it’s filling and finding rock after rock. Hammer and a 2×4 took care of it all!!!!

  14. Hi Dan. My questions are, do you recommend sand or fine ground stone for above ground pool base AND is it necessary or beneficial to put some kind of foam barrier over the sand or stone? Also, do you recommend pool wall foam? And duct taping the seam where metal pool wall meets? Foam cove for inside perimeter?? Sorry for all the questions, just don’t want to get oversold. Working on tight budget, but don’t want to skimp and be sorry in the long run. Looking at 27 – 30 ft round. Thank you.

    1. Hi. Let me answer your questions with articles

      Maybe sand, probably not ground stone https://abovegroundpoolsknowitall.com/does-an-above-ground-swimming-pool-need-a-hard-base-material/

      Wall foam? https://abovegroundpoolsknowitall.com/when-to-buy-and-use-wall-foam-for-an-above-ground-pool-read-this-before-buying/

      I use duct tape for that. two layers.

      Foam cove yes

Leave a Reply

Your email address will not be published.

Recent Posts