Four Things to do When you Open a Pool with Crystals in it

What are you going to do if you remove a winter pool cover and find calcium crystals in the pool? If you have encountered the winter crystals in the past--and you may have thought it was 'scale'--what did you do in the past? Did it work? This article will outline four things Orenda recommends if you are trying to open a pool with crystals in it.

Pool Crystals are NOT Scale

Just because they are calcium carbonate (usually), these crystals are not the same thing as scale. They should not be treated the same way. The problem here is more than just semantics! If we call crystals "scale", we are likely to continue scale-fighting habits, like keeping calcium hardness levels on the low side (200 ppm or less). We see it all the time. The problem we are dealing with here is the lack of calcium hardness and LSI balance in the winter. In other words, we need more calcium when the water is cold, so that the LSI can remain balanced. Cold water is more aggressive.

4. Prepare for crystals before arriving

If you winterize your pool(s), be on the safe side and prepare for spring openings. Assume you will encounter at least one pool with crystals. What will you need to rectify the problem? An accurate test kit, water thermometer, the Orenda App's LSI/Dosing calculator, Calcium chloride, sodium bicarbonate, and SC-1000. Also, be sure to have some empty buckets on your truck so you can pre-dissolve calcium and/or bicarb prior to adding it to the pool.

calcite crystals underwater

If you have a vinyl liner or fiberglass pool, do not expect to find crystals in it. Calcium crystals have to come from somewhere...and if your water is deprived of calcium, a liner will not provide that calcium. That said, rectifying the LSI is still your number one priority when opening the pool.

3. Test water chemistry thoroughly, and collect crystals as samples

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You will need a test kit AND a thermometer. Test for everything you can: water temperature, pH, total alkalinity, calcium hardness, cyanuric acid and TDS/salt. Plug those results into the Orenda App and decide how to balance the LSI of the pool.

When you test the water, keep in mind that cold water will often give false readings. It is best to grab a sample of water in a clean bottle and warm it up. Once the sample is warm, test. Do not be fooled by water chemistry that drifted up (or in the case of pH, spiked) in the winter to find LSI equilibrium. Those high chemistry readings happened at the expense of your surface.

Related: Cold water and the LSI

If you do encounter a pool with crystals, chances are, the chemistry will be surprisingly high. It's the opposite of what we would expect, right? In fact, in most cases we have seen, these pools have a pH above 8.0, and a calcium hardness level significantly higher than what the pool was closed with. Why? Because the water sought LSI equilibrium on its the expense of your surface. "Drift up" anyone?

Using our Orenda LSI Calculator App, you can see the impact that water temperature plays. It is our belief at Orenda that water temperature is the main driving factor for aggressive water in the winter. If you did not prepare for the cold water when you winterized, chances are, your water found equilibrium on its own...or at least tried.

Collect samples of your crystals

This is important! For our industry to better understand the winter crystal phenomenon, we need samples. Please collect them in a ziplock bag or other container, and contact us. Orenda is working in coordination with some leading organizations in the pool industry to figure these crystals out. We will facilitate getting the samples to the right people so they can be laboratory tested. At the time of this article, we still do not know the chemcial composition of all these crystals...nor do we know how many different types exist. Please help us learn more--we will share the information to better help you in the field.

Calcium crystals -calcite

2. Balance the LSI

The Orenda App should have guided you on what you need to add to the pool. Remember, the pool water should have found equilibrium on its own when the water was cold. Crystals and winter dust are evidence that the water balanced itself. If you see crystals, it tells us your water was hungry for calcium in the winter as the water got colder, and took calcium from the surface.

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It is our recommendation that you manipulate the calculator down to an ideal 7.4 pH on the left, under "current readings". This will allow you to more accurately identify how much calcium and alkalinity the water really needed before the pH drifted up. You can always adjust pH later...what is important now is building the foundation for LSI balance. And as the water warms up, you can adjust the pH and alkalinity down with acid as needed.

Normally, crystals and winter dust occurred because of a lack of calcium hardness in the winter.

1. Purge the pool with SC-1000

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After you have tested the water, used the Orenda app, identified how much calcium and/or bicarb to add (and have successfully added them the right way), the hard work is done. All that's left is to brush and add SC-1000 to gently dissolve the crystals back into solution.

We currently know of four distinct types of calcite crystals, and SC-1000 seems to only break down two of them. If your crystals are not softening or going away after a week of use, it may be a type of crystal that is more stubborn. In that case, unfortunately you may need to drain and manually remove them. We have seen plenty of pools with crystals that did nothing when directly acid washed. It is a strange (and vicious) phenomenon.


The best defense against calcium crystals is a good proactive winterization strategy. Such a strategy involves preparing for the winter months by adjusting your calcium, alkalinity and pH in preparation for cold water. We also suggest periodic winter visits to continue to adjust LSI.

Related: LSI Balance and Calcium Management (Pillar 1)

If you DO have a pool with crystals, following these four steps should help you rectify the problem as well as you can. Unfortunately, the damage is done, but this four-step procedure should help you mitigate it further. Let us know if you need help in the field. You can request an Orenda visit or training here.

For more information on how to close and open pools the Orenda way:

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