Winter Pool Care in Las Vegas: What Actually Changes?

You don't winterize a pool in Las Vegas or Henderson the way people do back East. No draining it down, no blowing out lines, no tarp. You keep it open and running on winter settings: shorter pump hours, a closer eye on pH and alkalinity, freeze protection turned on, and weekly cleaning that doesn't stop just because nobody's swimming.

This week is a good reminder. After highs in the low 80s to start the week, a storm is bringing rain, 25–35 mph gusts and highs in the low 70s to the valley Wednesday and Thursday. Winter is knocking.

Do you need to close your pool for winter in Las Vegas?

No. And please don't.

Our winters are mild. Based on NOAA's 1991–2020 normals for the North Las Vegas station, the first frost usually shows up around December 1 and the last one around February 11. We get a handful of cold nights, not months of ice.

A pool that sits without circulation, even for a few weeks, turns green faster than you'd think. Leaves blow in, dust settles, and stagnant water is exactly what algae likes. Closing a pool here usually means paying to clean it up in March.

So the pool stays open. It just runs differently.

How many hours should a pool pump run in winter?

Fewer than in summer.

Cooler water and weaker sun mean slower algae growth and less chlorine burning off. Most pools can cut back noticeably from summer run times. The exact number depends on your pool size, your pump and how much debris your yard throws at it, so we set it pool by pool instead of guessing.

A couple of rules hold for everyone:

• Don't turn the pump off for the season. Water still needs to move through the filter every day.
• If you have a variable-speed pump, longer hours at a low speed usually beat short blasts at high speed. It's quieter and cheaper.
• If your timer reset after a power outage or one of this week's storms, check it. A timer stuck on 3 a.m. to 4 a.m. is not a filtration plan.

If you're curious how pump timing fits with NV Energy's new daily demand charge starting January 1, we covered that in our post on the demand charge and your pool pump.

Why does pool water chemistry change in winter?

Here's the part most people don't expect. Cold water is more aggressive toward plaster.

Pool chemists use something called the saturation index (LSI) to measure whether water wants to dissolve calcium or leave it behind. Temperature is part of that math. When water drops from summer temps into the 50s, the index drops too, even if nothing else changed. Water that was balanced in August can start pulling calcium out of your plaster in January.

Orenda, a pool chemical maker, describes what that looks like: etching, rough spots, and a fine white dust on the floor in spring when the water warms back up. That damage doesn't come back.

The good news for us? Las Vegas tap water is already hard, around 280 ppm, so calcium is rarely the problem. Low pH and low alkalinity are. Winter rain, like this week's storm, can knock both down.

What we keep an eye on in winter:

• pH and total alkalinity, especially after a storm
• Calcium hardness, so we're not overcorrecting the other way
• Chlorine, which still matters even when algae slows down

Does a salt water pool work in winter?

Yes, but your salt cell may take the winter off without telling you.

Many salt chlorine generators cut back production as the water gets cold, and some shut off completely. For Hayward AquaRite units, output typically drops around 60°F and can stop below 50°F, depending on the model. The display might look fine. The chlorine just isn't being made.

That's how a salt pool that was perfect in October goes cloudy in January.

If you have a salt pool, test chlorine weekly all winter. You may need to add liquid chlorine by hand until the water warms up. It's also a good time to clean the cell, since our hard water loves to crust them over.

What does pool freeze protection do?

Most automation systems from Pentair, Hayward and Jandy have a freeze protection setting. When the air temperature drops below the set point, the pump turns on and keeps water moving through the pipes so it can't freeze in place.

A few things to know:

• Make sure it's turned on before December. It's often set during install and never looked at again.
• On a Hayward OmniLogic, freeze protection runs the filter pump and can override some other features, like heating, while it's active. That's normal.
• Above-ground plumbing at the equipment pad is what's at risk here, not the pool itself. A cracked pump housing or valve is the usual casualty.
• If you don't have automation, run the pump overnight on the few nights the forecast calls for freezing temps.

Henderson tends to run a few degrees colder than the middle of the valley on cold mornings. One November 2023 freeze watch forecast 33° in Henderson and 38° in Las Vegas.

What else should you do in fall and winter?

A short list:

• Empty the skimmer and pump baskets more often. Fall leaves and wind (hello, this week) fill them fast.
• Brush the walls and steps. Algae grows slower in winter, not never.
• Watch your auto-fill. Evaporation drops a lot in winter, so if the auto-fill keeps running, you may have a leak.
• Check your heater before you need it for a holiday swim, not the morning of.
• Keep weekly service going. Skipping December and January is how pools turn green by February.

Want us to handle the winter switch?

That's what weekly service is for. We adjust run times, keep the chemistry balanced for cold water, keep an eye on salt cells and freeze protection, and empty the baskets after every windstorm.

We service pools across Henderson and Las Vegas. Call or text us anytime at (702) 608-5226. We're open 24/7.