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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.

1. Prepare for the worst, Hope for the best

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Having Sodium Bicarb and Calcium on your service truck helps balance the LSI.

If you winterized your pools, be on the safe side, and prepare your service vehicles for spring openings. Assume you will encounter at least one pool with crystals. What will you need to rectify the problem? Calcium chloride, sodium bicarbonate, and SC-1000Be sure to have some empty buckets on every truck, so you can pre-dissolve calcium and/or bicarb prior to adding it to the pool.

Prepare for the crystals by having bags of calcium and sodium bicarbonate on your truck. You may also need our SC-1000, which is a non-acid-based chelant to dissolve the calcium back into solution. Don’t be fooled by high water chemistry that drifted up in the winter to find LSI equilibrium. Those high chemistry readings happened at the expense of your surface.

If you have liner pools, do not expect to find a liner pool with crystals in it. The 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.

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

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. Using the app, find out what it will take to balance the LSI of the pool.

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This water was tested by a customer during opening day 2017. The pool was covered in calcium crystals, yet the pH was well above 8. It is evidence that water ‘drifts up’ when it is aggressive, because it is finding equilibrium on its own. Colder water needs higher pH to stabilize 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 own…at 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.

3. Balance the LSI of every pool with crystals in it

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. We at Orenda believe that a pool with crystals is evidence of calcium being leeched out of the plaster surface due to a low LSI. 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 walls. Do not be fooled by a high pH…even if our Orenda LSI calculator indicates your water should be scale-forming (high LSI). That pH drifted up at the expense of your walls.


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.

4. Purge the pool with SC-1000 Scale & Metal Control

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SC-1000 is a chelant designed to keep metals in solution. It can gently break down various forms of calcium, including most crystals we have seen. It has a 10.8 pH, meaning it will not further lower your water’s LSI.

After you have tested the water, used the Orenda app, identified how much calcium and bicarb to add (and have successfully added them the right way), the hard work is done. All that’s left is adding SC-1000 to gently dissolve the crystals back into solution. NOTE: if what you have are actually calcium sulfate crystals, SC-1000 alone may not be enough. Calcium sulfate crystals can be a different problem entirely…though they can look similar. Contact us for further guidance if the SC-1000 does not remove your crystals within two weeks.

SC-1000 Scale and Metal Control is a metal chelant. Since calcium is, in fact, an alkali earth metal, SC-1000 can break it down and chelate it. The effect is similar to sequestration, except that most sequestering agents are acid-based. SC-1000 is an alkaline (10.8 pH) product which will not further lower your LSI. Since you’re combatting a low-LSI condition, why would you lower the LSI further?


The best defense against calcium crystals is a good offensive 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.

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 on how to start up pools the Orenda way: