How to Protect Your Fiberglass Pool During a Texas Freeze

San Antonio winters are mild most of the time, which is exactly why a hard freeze catches so many pool owners off guard. One night in the 20s is enough to crack a pump housing or split a pipe that has been fine for years. The good news: a fiberglass pool handles cold weather well, and protecting it takes a little preparation, not a full winterization.

Here is what to do before, during and after a Texas freeze, written for homeowners from the Hill Country to New Braunfels.

When freezes hit San Antonio and the Hill Country

San Antonio's average first freeze arrives around November 30, according to KSAT's review of local weather records. In the Hill Country it comes earlier: Boerne and Canyon Lake typically see their first freeze in early to mid November. Most years bring a handful of freezing nights between then and late winter, and every so often a long, deep cold snap like the February 2021 winter storm reminds everyone why preparation matters.

If you live in a cooler spot, such as a low-lying lot near a creek or out in the hills around Boerne, plan on getting ready a little earlier than your friends in the city.

Why fiberglass pools handle cold weather well

The pool itself is rarely the problem. A fiberglass shell is one solid, flexible piece with a smooth gelcoat surface, so there are no plaster cracks or tile joints for water to get into and freeze. Ice that forms on the surface during a short Texas cold snap is usually a thin skin that melts the next afternoon.

The weak points are the pieces that hold small amounts of water: the pump, the filter, the heater, valves and any plumbing above ground. Water expands as it freezes, and that expansion is what cracks equipment. That's why everything below focuses on your equipment pad.

How your pool was installed matters too. Staycation pools are set on crushed stone backfill with a de-watering sump, part of our advanced installation methods, which helps manage groundwater around the shell through every season.

Before the freeze: a quick checklist

Once the forecast shows temperatures at or below freezing, take care of these steps during the day, while it is still warm enough to work outside:

• Keep the pool full. Water should sit at the middle of the skimmer opening. Never drain a fiberglass pool to protect it from freezing.
• Clean the filter. Backwash or clean it so water flows freely all night.
• Check your freeze protection. Many pool automation systems have a freeze setting that starts the pump automatically when it gets cold. Make sure it is turned on and working.
• Insulate exposed pipes. Wrap above-ground plumbing and valves with pipe insulation, foam pool noodles or old towels and blankets.
• Balance your water. Cold water still needs sanitizer. Check chlorine and pH before the cold front so you are not dealing with algae when it warms up.
• Pull the robotic or suction cleaner. Take it out, drain it and store it in the garage.
• Know where your breakers and drain plugs are. If the power goes out, you will want to find them quickly, in the dark and the cold.

During the freeze: keep the water moving

The most important rule is simple: keep the pump running the entire time temperatures are at or below freezing, overnight included. Moving water freezes far more slowly than still water, and circulation keeps water moving through the pipes and equipment where damage happens. If you have a variable-speed pump, run it at a higher speed than usual during the cold snap.

Open all of the valves so water flows through every line, including spa and water feature lines. Water sitting in a closed-off pipe is the water most likely to freeze.

A few things to avoid:

• Don't break the ice. If a thin layer forms on the surface, leave it alone. Hitting it can damage the pool or hurt you, and it melts on its own once the sun comes up.
• Don't put space heaters, heat lamps or electric blankets near the equipment. They are a fire risk around pumps and filters.
• Don't rely on the heater alone. A gas heater can help during a short cold snap if it was already running before the freeze and the pump stays on, but it is not a substitute for circulation.

If you have a salt system, keep in mind that many salt chlorine generators slow down or stop producing chlorine when the water gets cold. Check your owner's manual and plan to test your chlorine level once the weather warms back up.

If the power goes out

A freeze plus a power outage is the combination that does the most damage, because the pump stops and the water in your equipment sits still. If you lose power:

• Turn the pool equipment off at the breaker so nothing restarts on its own in a damaged state.
• Open the drain plugs on the pump, filter and heater so water can drain out of the equipment instead of freezing inside it.
• Leave the pool itself full. The shell is not what needs protecting.

When power comes back and temperatures are above freezing, close the drain plugs, turn the breaker back on and restart the system carefully using the steps below.

After the freeze: inspect before you restart

Once the cold front passes, give your equipment a quick look before going back to your normal schedule:

• Open the air relief valve on top of the filter to let out trapped air and pressure.
• Look over the pump, filter, heater, valves and visible pipes for cracks. Even a hairline crack can leak or fail under pressure.
• Prime the pump and watch for leaks. If it won't prime after another try, turn it off and call a pool professional.
• Check the skimmer, waterline and any water features, then test and balance your water.

If something did crack, shut that part of the system down and call for service before running it again. Running damaged equipment can turn a small repair into a bigger one.

Planning a new pool? Think about freezes now

Winter is also the season when many San Antonio families start researching a pool, and it's a good time to plan for cold weather from day one. Ask about automation with built-in freeze protection, equipment placement that is easy to reach on a cold night, and insulated plumbing at the pad. These are small decisions during design that make every winter easier.

If you are starting to plan a backyard pool, our team can walk you through fiberglass models, equipment and freeze-ready design during a free consultation. Explore our pool models or book a consultation to get started.