A Complete Guide to Cleaning the Pool Waterline

The pool of your dreams is in your backyard. There is space for you and all your family and friends, sparkling clean water, and a deck that would make any neighbor jealous, but what about that nasty waterline? What are the different ways you can clean a pool waterline? 

To effectively remove calcium silicate at a pool’s waterline, you can either use a high-quality pumice stone or a professional calcium remover. For the removal of calcium carbonate, you can either use a calcium releaser or a stain eraser to remove the affected areas of your pool. 

Few things ruin the aesthetic of a pool more than a dirty waterline creeping up the sides. It is unsightly, makes the area seem and feel dirty, and can be an area of serious stress if you cannot find the right method for removal. Continue reading to figure out what is causing your pool’s waterline to be discolored and how to remove unsightly waterline marks without having to call in the professionals. 

What is Causing Your Pool’s Waterline to be Discolored? 

When you look out at your pool, the only thing you want to be thinking about is how much fun everyone within it is having, how pristine the water is, how beautiful your landscaping looks around it, and how great you are about to look lounging beside it. The last thing you want to think about is an atrocious waterline that has built up over weeks or even months. Gone are the days of being carefree, you have a problem on your hands now. 

Ideally, a pool’s waterline should be relatively seamless. You should be able to look at where the top of your water stops and watch it flow with ease up against the lining of your pool. When the water is moved from its usual position you should not be able to see where the water typically sits. 

For example: Consider what your pool looks like when there is a big group within it. It is unlikely that the water remains calm, flat, and even glass-like. More than likely, the water is being pushed in every different direction and it retracts from its typical resting position against the pool liner. When this retraction happens, you do not want to see a line that has found its way to the pool liner. You want a clean lining with absolutely no residue. 

However, if you do see that there is a mark scaling even a segment of your pool or the entirety of its inside parameters, you may be wondering what that line is made up of. Sometimes it can be easily wiped away, but other times it takes a bit more effort to completely rid your pool of its stain. 

For most pools, a pool water line is made up of two common types of scaling: calcium silicate or calcium carbonate. Knowing which type of water line you are seeing can help to find a more effective removal process.

What is Calcium Silicate? 

Calcium silicate is one tough substance when it comes to how easily (or not easily, for that matter)  it can be removed. This is a type of calcium (as its name implies) that is caused by an imbalance in your pool’s chemical levels, and it takes its time building up. 

This means you are not going to see it pop up overnight, but it will slowly make its way along your pool’s waterline and will build up day by day. It is more of a white-gray color and is relatively compact in its structure which makes it very difficult to remove. 

This type of waterline build-up requires a more specific removal approach. In essence, you are not going to be able to clean this by just rubbing a multi-surface cleaner onto it or by just trying to wipe it off.

Therefore, if you want to test for calcium silicate along your pool’s waterline, place a few drops of muriatic acid on either a sample or on a small portion of the waterline and wait to see if foaming occurs. If there is no foam, you unfortunately have a case of calcium silicate. 

We will discuss how to remove this effectively a bit further down in this article. But, in case your pool waterline is not calcium silicate, there is one other common option to check. That is calcium carbonate.

What is Calcium Carbonate? 

Calcium carbonate is also a type of scaling that is caused by an imbalance in pH levels. This type of scaling is much easier to remove than calcium silicate and looks a bit different as well. When calcium carbonate builds up along your pool’s waterline, it is going to look flaky. 

When you touch it, it will either peel off in small sections or will flake off from very little friction. It is also a brighter white than calcium carbonate and is very rarely gray. Of course, this appearance will make it highly distinguishable, so you likely will not have to run the same type of tests, but it is encouraged to be sure that this is what you are dealing with.

If you cannot tell by appearance if the residue at the waterline of your pool is calcium carbonate, you can use the same method as suggested with calcium silicate. Simply place a few drops of muriatic acid along the waterline of your pool and wait for a reaction. If the residue begins to bubble and foam, it is calcium carbonate. Lucky for you, this means a much easier removal with significantly less time cleaning the waterline up. 

How to Remove a Calcium Silicate Pool Waterline

With calcium silicate being the tougher of the two scalings to remove from your pool’s liner, it is important that you first identify if this is in fact what you are dealing with at your pool’s waterline. If after your muriatic acid test there is no reaction and you have confirmed that this is the build-up along your pool’s waterline, you need to proceed with its removal. 

There are a few ways that it can be removed, but be very careful with the process, so as not to mess up the lining of your pool or cause further damage elsewhere. Two ways to remove a pool waterline made of calcium silicate include: 

Pumice Stone 

With the nature of this scaling being so hard, it makes perfect sense that the material to remove it would be hard as well. A pumice stone is really just about the only scrubbing tool that will help ride your pool’s waterline of the gunk, but beware. If you have a glass edging, plexiglass, or a soft liner, the pumice stone can very easily scratch or rip the area. In this case, you would not be able to use a pumice stone for calcium silicate removal. 

Professional Calcium Remover 

If a pumice stone is not an option for you, try using a professional calcium remover. This can be purchased at your local pool store and can be applied without the need or professionals. Be sure to apply it to a small area first to see how the surface reacts to the product. Once you know there will not be any issues, continue the process over the entirety of the pool’s waterline or to the areas that are affected by calcium silicate. 

How to Remove a Calcium Carbonate Pool Waterline

For all of you pool owners who have a mark along your pool’s waterline and know that it is calcium carbonate, you are in luck. Although no one wants to encounter problems with their pool, the presence of calcium carbonate is one that will not give you too much trouble and likely, can be easily removed within a few minutes. 

Even better, this removal can happen through the aid of items you likely already have around your house. If you have a calcium carbonate pool waterline, consider these options for removal:

Calcium Releaser 

Calcium releaser is a product that can be extremely effective on calcium buildup but is not as harsh as a professional calcium remover. You can find calcium releaser at your local pool store as well and you may even be able to spot some at a local hardware joint. Simply spray this onto the affected area and scrub with either a pumice stone (do not use this if you have a glass, fiberglass, or vinyl lining) or a coarser sponge. 

Stain Eraser 

Stain erasers are like the Magic Erasers for pools. They are made from a surface-safe polymer with a very mild abrasive built into the eraser to help scrub away at calcium deposits. These are great because they require no extra tools and can usually swipe away calcium carbonate without you having to put in an excessive amount of scrubbing and you don’t run the risk of puncturing or scratching the siding of your pool. 

Do You Have to Drain a Pool to Clean It?

Now that we have discussed the more specific ways on how to clean your pool waterline based on what the root of the problem is (either calcium silicate or calcium carbonate, most likely), you might be curious about a few of the basic components for cleaning your pool. For example, what do you need to do about draining your pool?

You should not have to drain your pool to clean the pool waterline, although you will want to avoid the use of your pool for 3-5 days or until you can confirm that the pool’s chemical balance has been restored to normal levels. To clean a pool’s waterline, you can carefully lean from above the edge of the pool and work your way around.

Of course, it is nobody’s dream to have to lean over the edge of the pool, and it can become a bit dangerous once your muscles are growing tired and weary of cleaning the pool. This is why regular maintenance is highly preferred and encouraged so that this type of cleaning tactic does not have to be induced. 

Still, you should not have to drain the entire pool to clean it- or even just the waterline, and you should avoid draining your pool more frequently than necessary for the upkeep and costs involved.

Jed Arnold

Jed spent every year from the ages of 15 - 22 as a Lifeguard (Red Cross) and ages of 17 - 22 as a Certified Pool Operator (CPO). Between working for over a dozen facilities and owning a pool, he carries over a decade of pool experience.

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