Low Temp Mode

Crystal continuously monitors your water temperature and uses it to fine-tune the care recommendations it gives you. When your pool's average water temperature drops below 65°F, Crystal automatically switches into Low Temp Mode.

Low Temp Mode changes the sanitizer recommendations Crystal makes.

Why temperature matters

Chlorine chemistry and pool usage both shift as water cools:

• Salt chlorine generators lose efficiency in cold water. The electrolysis process that converts dissolved salt into chlorine relies on temperature-dependent chemical reactions. Below roughly 65°F, most salt cells can no longer generate chlorine fast enough to keep up with normal sanitizer demand — even at full output.
• Chlorine demand generally drops in cold water. Colder pools are used less often, and lower temperatures slow the growth of algae and bacteria. That means the pool typically needs less active sanitizer overall to stay safe and clear.

Because these two effects point in different directions, Crystal treats salt and chlorine pools differently once Low Temp Mode kicks in.

Salt Pools

What changes: Once your average water temperature drops below 65°F, Crystal starts recommending you add a slow-release chlorine tablet regularly in addition to your normal salt cell operation. The slow-release chlorine recommendation interval is adjustable in the pool settings.

Why: Your salt cell is still running, but it's no longer a reliable sole source of chlorine. Below 65°F, the electrolysis reaction inside the cell slows down significantly, and most generators simply can't produce chlorine fast enough to maintain a safe residual — regardless of how you have the output percentage or run time configured. If nothing were adjusted, this could allow free chlorine to fall too low, opening the door to algae growth or unsanitary water even in cold conditions.

Adding slow-release chlorine bridges that gap. Slow-release chlorine provides a steady, low-level chlorine supply without relying on the salt cell — effectively acting as a backup sanitizer source while your generator is underperforming.

Adjusting the interval: Every pool is different — tablet feeder type, pool volume, bather load, and even how sheltered the pool is can affect how quickly chlorine gets used up. If you find you're consistently over- or under-chlorinated in Low Temp Mode, you can adjust the 2-week default interval in the pool settings to better match your pool's actual demand.

What to expect when temps rise again: Once your average water temperature climbs back above 65°F, Crystal will exit Low Temp Mode and return to its standard salt pool recommendations, and the slow-release chlorine recommendations will stop.

Chlorine Pools

What changes: For pools that use slow-release chlorine(tablets) as their primary sanitizer, Low Temp Mode slows down (lengthens) the recommended interval between tablet additions.

Why: Chlorine pools typically have a reduced chlorine demand during with colder water temperatures:

• Used less frequently (fewer bathers introducing contaminants)
• Less prone to algae growth, since algae growth slows dramatically in cooler water
• Generally lower in organic and chemical chlorine demand overall

Adding slow-release chlorine at your normal warm-weather interval in this situation would over-chlorinate the pool over time, wasting chlorine and pushing stabilizer (cyanuric acid) levels higher than necessary. By stretching out the interval, Crystal keeps your chlorine residual in a healthy range without overdosing a pool that simply isn't being used or challenged as much.

What to expect when temps rise again: As soon as the average water temperature moves back above 65°F, Crystal exits Low Temp Mode and returns your tablet interval to its standard warm-weather recommendation.

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