Why you Cannot Use a Different Sized Liner in an Above Ground Pool

During my now 37 years of installing above-ground pools, I have been asked about installing a liner that is a different size than the pool a few times. I have to tell them that you can’t.

REASONS WHY SOMEONE WOULD WANT TO INSTALL A DIFFERENT SIZED LINER INTO THEIR ABOVE GROUND POOL

Matching a liner with an above-ground pool is pretty straightforward. You find out what size pool you have and what the height is and then you get a liner made for that specific size.

An example of this would be that you have a 24’ round pool 54” high. You would get a liner that would be for a 24’ round pool that is either an overlap(which can install in any height) or a j-hook/unibead for a 54” height.

Reasons why you might consider installing a liner other than the exact size for your pool.

1. They bought or received the wrong size liner

Some will mistakenly get the wrong sized liner and think about installing it anyway. Yeah, no.

2. They found a slightly different sized liner for a really, really good price

I have had people get liners for super cheap or free but is not the size of their pool. It’s close to the same size, but not the same.

Sorry. Even a wrong-sized liner that was free is not worth installing. Buying a different sized liner for your pool because it was almost free is like buying cheap cat food when don’t have a cat.

3. They have a pool with a super deep center or end and think that they can use a slightly bigger liner to make it fit

Pools with especially deep bottoms can use what is called an expandable liner.

If a pool has a crazy deep end or center (like three feet deeper), then they should purchase a custom-made liner.

4. They cannot find a liner that is the size of their pool for sale anywhere

Most above-ground pools are made in very common sizes, but not all. Some smaller manufacturers will make an odd size that requires a custom-made liner.

When you buy one of these uncommonly sized pools, they come with a liner. Some years later when it’s time to replace the liner, people can find their size, so they will see if a readily available sized liner that is close will work for their pool.

So sorry. It will not. If you can’t find the same size liner for your pool, then you’ll have to have one custom-made.

WHY DO YOU HAVE TO USE THE SAME SIZED LINER FOR AN ABOVE GROUND POOL

Vinyl pool liners are not made in just one piece. They are made in a few pieces that are fused together in seams. All above-ground pool liners have one, two, or three pieces of vinyl that make up the bottom and then one, two, or three pieces that make up the wall or the pool.

Each liner then has a seam that connects the bottom pieces to the wall pieces. So, round pool liners have a round seam that runs along the bottom of the wall all the way around. And oval liners have an oval-shaped seam that runs along the bottom of the wall.

This round or oval-shaped seam is what makes the shape of the liner. It’s what makes a round liner fit well in a round pool and an oval liner fit well in an oval pool.

Liners then have a different-sized round or oval pieces that make up the bottom. As an example, a 24’ round liner will have a round bottom piece that is around 23’, 10”. And an 18’ round liner will have a bottom piece around 17’, 10”.

Above ground pool liners are made to be slightly smaller than the size of the pool so they can stretch into a perfect, wrinkle-free position.

WITH A LINER BIGGER THAN THE SIZE OF THE POOL, THE BOTTOM PIECE WILL RIDE UP THE WALL OF THE POOL

If you tried to install a 24’ liner into a 21’ pool, then the bottom piece of the liner would be about 23’,10”. This means that the round seam of the liner would be about one foot bigger than the pool’s bottom and would ride up the wall.

This bigger bottom piece would create a lot of excess dimension around the pool’s wall. This means a lot of extra vinyl material, which equates to a lot of really big, vertical, folding wrinkles running up the wall. Not good.

WITH A LINER SMALLER THAN THE SIZE OF THE POOL, THE BOTTOM PIECE WILL BE MUCH SMALLER

Let’s say now that you are trying to install a 21’ liner into a 24’ pool. With this, the liner’s bottom piece will be about 20’,10”, which is about 18” smaller than the pool’s bottom.

This smaller bottom piece has the vinyl wall pieces attached to it at the round seam. Since the bottom piece of the liner is so much smaller than the pool, you will not be able to pull the sides(wall) of the liner to the wall of the pool. It will reach some of the top of the wall, but not all the way around. Not even close.

You will not be able to make this fit as the wall part of the liner would have to stretch sideways way too much. l

EVEN A LINER VERY CLOSE TO THE SIZE OF THE POOL WILL NOT WORK

You might think that you could make a liner that is very close to the size of the pool work. It will not.

A while back, Wilbar made a 20’ round size for their then-new “Matrix” model. This was an uncommon size, so some could only find the standard 21’ liner for a replacement.

Even though the difference in size is only one foot, a 21’ round liner would be waaaaay too big for a 20’ round pool. It would leave a lot of really ugly vertical, big wrinkles going up the pool’s wall everywhere. You may be able to get the bottom winkle-free, but not the sides.

And the reverse wouldn’t work at all. You would not be able to stretch a 20’ round liner over a 21’ round pool’s wall all the way around. It just can’t stretch that much in that way.

I HAVE INSTALLED A COUPLE OF BIGGER SIZED LINERS AND IT WAS UGLY

Many years ago (probably when cassette tapes were common), I installed a 15×26 liner into a 15×24 pool.

Now, this was about as close as you can get to a different size liner going into a pool. It didn’t matter though.

It was the off-season when the pool owner called me. He told me he got the wrong sized liner for his pool and could I install it anyway. I told him that I wasn’t interested as the finished liner would look really bad.

He then said that it didn’t matter what it looked like to him. He was only going to be in that house for a few months and just wanted a pool and didn’t care. Since it was my off-season and I was probably broke, I agreed to do it as long as his expectations were very low. He convinced me that he knew it would look bad, so I did the job.

When I was done, the liner looked really bad, I did as good as could be done, but it still had some really big vertical folds running up the wall and a few choice wrinkles along the bottom corners of the oval. He was happy that he had something holding water and I was happy to get paid, so all was good, but the pool looked horrible.

SMALLER SIZED LINERS WILL ABSOLUTELY NOT WORK IN BIGGER POOLS

Even though a bigger liner installed in a smaller pool will look horrible with folds and wrinkles, it will work to hold water. The opposite will not work though.

A smaller-sized liner will not stretch horizontally enough to fit into a bigger pool. I have attempted this over the years as well and was never able to make one fit. Not even close.

YOU CANNOT USE DIFFERENT SHAPED LINERS EITHER

Just to be clear, you cannot use a round liner with an oval pool, an oval liner with a rectangle pool, a rectangle liner with a round pool, or the other ways around.

Remember that each liner has a shaped bottom piece which means it won’t fit well in a different shaped pool.

SOME LINERS THAT ARE THE CORRECT SIZE BUT A DIFFERENT HEIGHT CAN WORK

For the most part, you want to match the liner height with the pool height as well. There are some exceptions though where you can make certain liners work with different pools.

1. Overlap liners will work with all wall heights

Many overlap liners will have a product description that says something like 48” – 52”. This means that it’s made to fit both 48” and 52” height above ground pools.

The majority of these liners will work with a 54” high pool as well. I would like to say “all” of them will, but some won’t. If you have a cheaper Chinese made overlap liner, it may not have enough material to go over a 54” wall.

I have had maybe two liners not have enough material to go over a 54” walled pool. That was some years back though and they were Chinese-made liners.

Overlap liners are supposed to have 60”(five-foot) of wall material which should be more than enough to go over any sized pool wall with plenty of excess. I haven’t seen or heard of an overlap being too short in some years, so I think you are good to go.

2. 52” J-hook/uni-bead liners will work for 54” pools

As mentioned earlier, liners are made to be a little smaller than the pool so they can stretch perfectly in place. A 54” tall above ground pool is only two inches bigger, so the liner will have no problem fitting.

I install 52” made fixed top (J-hook/uni-bead/beaded) liners into 54” tall pools quite often with no issues.

3. A 54” J-hook/uni-bead liner can work with a 52” or 48” pool

This may not be as easy a fit as installing a smaller liner into a bigger pool, but it’s doable.

The fear here is that the liner will have too much wall material and the excess will make wrinkles/folds at the pool’s wall. And that can happen.

This bigger liner has to be installed like you would an overlap liner. You have to pull some of the top of the liner over the wall and then secure it to the top of the wall using plastic coping strips just like you would an overlap liner.

For a 52” wall, there won’t be much liner that has to go over the wall but it will be a couple of inches. And a 48” wall pool will have about six inches that you would pull over the wall.

This taller 54” liner will fit perfectly if you do this. The only negative to this is if the liner has a tile pattern, then some of that pattern will be unseen as it will go over the wall. Not a big deal really.

You may also need to get plastic coping if the pool you bought didn’t come with any.

4. An expandable liner can be used for a standard flat bottom pool

Some will have an expandable liner and not have a deep center or deep end in their pool. They may have planned on it, but there was something in the earth that didn’t allow them to dig a deep center. Or they got an oval and didn’t know that straps were running underneath it and they can’t have a deep end.

They now have an expandable liner with a flat bottom pool. No problem.

An “expandable” liner has a deceiving name. It’s NOT made of a different more stretchable material as the name would suggest. What it really means is that it has an extra 12” of wall vinyl material.

So if a standard overlap liner has 60”(5ft) of wall material, then an expandable liner has 72” (6ft) of wall vinyl.

Nothing else is different, so you can install it and it will fit perfectly. The only annoying thing is that it will have A LOT of extra material going over and hanging down the outside of the wall. You can cut that excess out later though.