As temperatures drop in North Texas, many pool owners turn to their gas heaters for peace of mind. However, running a gas pool heater when your water is below 70°F can cause thousands of dollars in internal damage, which is completely preventable.

At Simplified Pools, we see this same failure several times every winter, and it always comes down to one thing: Condensation inside the heater’s combustion chamber.

Below is a breakdown of why it happens, what to avoid, and how to protect your equipment and wallet this season.

What happened inside the Heater?

Gas heaters are designed to heat water efficiently—but only when conditions are right.

When very cold water (below 70°F) moves through a heater, it meets extremely hot combustion gases. This temperature difference creates heavy internal condensation, much like fog forming on a cold glass of water.

Inside a heater, that moisture becomes:

• acidic

• corrosive

• damaging to copper, steel, and internal components

• capable of completely rotting out the heat exchanger and lower housing

Over time, the condensation puddles and eats through the metal from the inside out. In severe cases, the bottom of the heater literally disintegrates.

This type of decay has nothing to do with water chemistry; it's purely mechanical condensation damage.

Why condesnstaion gets worse below 70F

Once pool water dips below 70°F, condensation skyrockets.

Some of that moisture vents out, but much of it:

• collects inside the heater

• pools at the bottom

• repeatedly wets and dries the metal

• accelerates rust and corrosion

If you run your heater for hours or days trying to “keep the pool from freezing,” this damage snowballs quickly.

Do You Need to Heat Your Pool for Freeze Protection?

No. You don’t.

Your pool stays safe during freezing weather because the pump circulates water, not because the heater runs. The heater has nothing to do with freeze protection and should not be used for this purpose.

Heating a pool in freezing weather—but failing to bring the water above 70°F and keeping it there is the fastest way to destroy a heater.

Improper Water Flow Makes the Problem Worse

If your pump is running at too high of a speed:

• the water doesn’t heat enough on each pass

• the heater has to run longer

• condensation increases

• components wear out faster

This is common on systems with oversized VSF pumps or incorrect bypass valve settings.

What About Heating a Hot Tub?

Good news—this rule does not apply to hot tubs.

A hot tub heats up quickly, crossing the condensation zone within minutes. Yes, it will produce condensation until it reaches about 70°F, but the moisture doesn’t last long enough to cause damage.

Sprinkler Damage Looks Identical

We also see heaters ruined by sprinkler systems spraying up into the heater cabinet. That cold water causes the same corrosive condensation pattern and can void most heater warranties.

If your equipment sits near your lawn irrigation, be sure no heads are aimed toward your pad.

How to Protect Your Heater This Winter

Here are your winter best practices:

•  Don’t run your gas heater if your pool water is below 70°F; unless you plan to actually heat the pool above that threshold.

•  Never use your heater for freeze protection; circulation, not heat, keeps your pool safe.

•  Keep your flow rate within the correct range; Too much flow = more condensation.

•  Check for sprinkler overspray; cold irrigation water can destroy a heater in weeks.

Overall Impact

Condensation damage is one of the most expensive and most preventable winter pool problems. Taking a few simple steps can save you thousands.

If you plan to use your heater this winter or need help preparing your equipment, our team is here to help.
Reach out anytime—your pool is our priority. Contact Us Here