5 Steps to a Perfect Pool Liner Replacement


To be successful in the quest to replace your above-ground pool liner wouldn’t it be prudent to hear from a person with 25 years of replacement liner experience? I’ve seen it all and developed this safe method to help those with zero experience to trust their decision-making abilities when it comes to their own pool liner.

Simply going online and giving the dimensions of your pool to a sales staff and expecting a smooth outcome is impossible!

The 5 Successful steps to pool liner replacement

  1. Measuring your pool
  2. Inspecting your pool
  3. Researching pool liners
  4. The selection process
  5. Liner Installation

Step 1 How to measure your above-ground pool

OKAY, a new liner is necessary. Next, you’ll need to measure the pool for a new liner.

If you have a “round pool”, you will need to know the diameter and wall height. Oval and rectangle pools will need measurements for the length and width. You will also need to know information about the bottom of your pool.

How to measure a round pool

You will need two measurements for the round pool.

  • Diameter
  • Pool wall height
mission round
Mission Pool

In this example to the right, the pool has a total of 14 uprights. Since it is an even number you split that in half which is 7.

So you mark the #1 upright and count 7 uprights over being careful not to count the first upright.

Use your tape measure to determine the distance between the #1 upright and the #7 upright. This is the diameter of the pool. Do this step on the inside where the liner meets the pool top. You’ll have to measure underneath the top rail.

In this example to the right, the pool has 15 uprights. To get the halfway point you’ll need to first find the highest even number of uprights your pool has. In this example, that number is 14.

Again, count 7 uprights in either direction and be sure not to count the #1 upright when counting to the #7 upright.

Use a tape measure and measure from the #1 upright. Then go between the #7 upright and the next upright which is the #8 upright. This is the diameter of your pool. Write it own.

You can whip out a tape measure and do this the common sense way and it will yield good results. The following are the common-size “Round” pools. Your measurement should get you pretty close to one of the following standard pool sizes.

Pool Diameter in FeetApproximate Number of Uprights
(some pools have an odd number)
Round Pool Diameter chart

Next, you will need to measure the wall height.


Special Note: Don’t Measure wall height on the inside of the pool! OUTSIDE ONLY! Always measure from the outside.

Move any debris that may be in the way so you can measure from the base of the pool to underneath the top rail.
Use your tape measure and measure like this illustrated picture.
This is your pool wall height. Write this down!

The wrong height measurement will set you up to fail.

How to measure an oval pool, length and width

There are three measurements you’ll need for an oval pool.

  • Length
  • Width
  • Pool wall hieght
mission oval measure
Mission Oval

Sometimes the length measurement is from upright to upright. Sometimes it is between two uprights.

Take your measurements from the inside of the pool wall near the top of the pool. Use a tape measure and measure from the straight side to the other straight side. Write down your measurement.

Use a tape measure from one curved end to the other curved end. (this is the length dimension of your pool). Write down your measurement.

In this particular example of two different pool sizes. Notice how sometimes you will measure from one upright location to the other. But on some, you will measure from between two upright locations.

different oval sizes

Please note on oval pools:
Manufacturers build their walls in different lengths and have different upright locations.

For example, let’s say you have a 15’x30’ pool that measures 15’2”x30’1”, this is OK.

If it is so far off that it makes sense to have next sized liner. Then getting the next size makes better sense. It is possible you have an odd ball-sized pool. There are manufacturers that have come and gone and you could have a pool size that isn’t built anymore.

In this case, a search will need to be conducted to see if a pool liner manufacturer still makes this size pool.

So to recap round above-ground pool measurements you need the wall height and diameter. For an oval or rectangle, you will need the wall height and length x width.

A Few Common Above-Ground Pool Sizes

Round Pools in ftOval Sizes Pools in ft

Step 2 Pool Inspection

Part of the process of changing your pool liner will involve inspecting the pool. Do this while you while are taking measurements.

Even the best-looking pools can have major problems lurking past the naked eye.


Take a pool like this one here. Looks great right?
Vegetation and decks cause the most decay. The worst is mulch! If you see mulch around a pool? get a new pool! Of course, you’ll want to inspect first.

When you have vegetation growing close to the pool wall. You can end up having rust and rot issues because the greenery holds moisture close to the wall of the pool.

You always want to check the wall in several places no matter what is growing around the pool.

Also, check under decks for issues. Check out the bottom ends of the uprights to see if they are still attached with manufactured screws. Sometimes the screws can rust and break long before the pool’s uprights show any problems.

Material on the outside of the wall can mask the potential issues. So peel back whatever material you have to have a look.

You need not check every single upright but do check a few of them. Check about 3 or 4 if they are good then chances are the rest will be OK as well.

Rusty screws:

Your checking for rusted in place screws and top plates. If the first one is rusty don’t panic. You need to do a few to determine if it’s a task you are up for.

It is completely normal to have a few that are stuck in place.

A pool that has almost all the screws rusted into place. This will prove to be a pool you will be better to replace.

Most will OK, try spraying some WD-40 on all the screws that hold down the top rails on. You will also spray the screws underneath the top ledges. These screws hold down the top plates.

Rusty walls:

rusty pool
Rusty pool

Next, you will check the bottom of the wall of the pool. Look for rust coming through the wall. Any pool which shows rust coming through the wall will only be worse when the old liner is removed.

If rusted out this pool should be replaced.

Rust on a steel wall is nothing to mess with and needs special attention. You may need to further cut away the liner and look behind the liner.

The Weather and Pool Liner?

Needless to say, no pool liner should be replaced in cold weather. It doesn’t make sense to be out there in cold weather replacing anything to do with pools.

climate map
Climate Map

Rule number one don’t do it under 70 degrees! The liner will not be able to stretch the way it needs to do. Rule number two is that if the temperature is above 70 and below 95 then it is fine to replace a pool’s liner.

When the temperature is above 95 degrees it will be difficult to work. The liner becomes so big it is “size the liner”. We will get to sizing in a little while but for now, remember to be very careful in cooler and higher temps.

In colder climates like New England, there is a limited time frame for replacing a pool liner. We start in April and we continue to replace liners all the way into October. In warmer climates like Florida, you can replace it year-round. So a little common sense to weather is in your hands.

Skimmer and return cut outs

This part of your pool will need a good look when replacing a pool’s liner. Most leaks occur here!. So many pools have been lost due to leaky skimmers and returns.

When inspecting this area use a small screwdriver. One with a #1 tip or even an ole, a pointing metal handheld tool. Something to poke the wall and see if it’s tender in the stained areas.

When a skimmer or return leaks over time it will leave stains running down the side walls. Check this area by poking and see if it is weak.
If you are able to poke through then the wall needs replacement.

Pay special attention and inspect the openings of the skimmer and return. Look for worn-down metal. If the area shows obvious signs of damage. Address them.

On Pool Liner Warranties?

This is the most confusing part of the whole liner replacement process.

Warranties can seem too good to be true and carry lots of stipulations to get coverage in place. Extra warranty coverage can be obtained when purchasing a pool liner pad. Doing this will extend your liner warranty.

The fact is most manufacturers don’t cover liner leaks of any kind unless they are seam that’s failed.

The warranty is only applicable if you take the time and fill out your warranty paperwork.

So take this time as soon as you completed it. Do this even when a professional contractor replaces the liner.

We will explain all throughout this guide what to avoid.

The contractor can help you. Their knowledge about the whole process will go a long way in saving time and money.

Step 3 Liner Research

Which liner is correct for my pool? With the number of choices in today’s liner market, it is no wonder so many wrong decisions. Pool Liners have varying quality and terms the market uses. The following two videos explain the attachments and features of above-ground pool liners.

Step 4 Liner Selection

OK, so we have arrived at installation.

It is last in our guide but for you it may have been what brought you here, to begin with.

We like to think most people can do a liner replacement themselves. Yes, it can be a little challenging but if you know about all the secrets an installer uses it will be easy for you.

So your pool is looking good you have the right liner and it’s the correct size.

Step 5 Hiring the right contractor for Installation

Get someone who knows all the steps above and who can answer them and explain them all to you. Try doing it yourself? It’s not as hard as you might think.

I hope this article has helped you learn a little more about replacing your above-ground pool liner. At least it will give you a fighting chance. Good luck with your project!

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