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Why Does My Gas Water Heater Put Out Cold/Lukewarm Water In The Morning?

May 11, 2017

If you’re getting lukewarm showers in the morning, the problem could be that the water heater’s gas burners aren’t coming on overnight to keep your water hot. Yes, even if the water in the tank drops to lukewarm temperatures.

In this article, we’ll explain:

  • Why can't your water heater always keep water consistently hot?
  • Why is the water especially cold in the morning?
  • How to prevent cold showers.

Do you need a plumber to correct this now? Just contact us and we’ll send one over right away.

Why your water heater can’t always keep water at a constant temperature

Your water may be coming out at a lukewarm 90 degrees because your water heater’s thermostat doesn’t control the temperature precisely.

You see, your water heater’s thermostat is a long metal rod (or “temperature probe”) that expands and contracts as the water temperature rises and falls. As the rod expands/contracts, it turns the burners that heat your water on/off.

But because this metal rod wasn’t designed to control temperatures as precisely as, say, a digital thermostat, your water heater temperatures will fluctuate.

In fact, if you set your water heater thermostat to 120°F, the temperature could rise to 150°F or fall to 90°F, according to this State Water Heaters Instruction Manual.

“Due to the nature of the typical gas water heater, the water temperature in certain situations may vary up to 30°F higher or lower at the point of use such as, bathtubs, showers, sink, etc. This means that when the temperature adjustment dial is set at the mark approximating 120°F, the actual water temperature at any hot water tap could be as high as 150°F or as low as 90°F.” (Emphasis ours)

And because 90 degrees is substantially lower than the human body temperature (98.6 degrees), the water feels lukewarm or even cold.

“But why do I mainly get cold water in the morning?”

One reason is that the water sitting in the pipes is cold.

But if the water is still cold after a few seconds, then it could be because the water heater’s burners have yet to ignite.


Because the heater’s burner won’t start until AFTER you use hot water for the first time in the day, which is typically during the morning shower.

To understand why burners won’t ignite until AFTER you use hot water, let’s look at how your gas water heater works:

  1. Your shower draws a large amount of hot water from the water heater.
  2. Cold water refills the tank.
  3. As cold water hits the metal rod thermostat, the rod expands, turning the gas burner on.
  4. As the water heats, the metal rod contracts, turning the gas burner off.

So, after your shower, the burners come on and heat the water in the tank. And as you continue to use hot water throughout the day, cold water continues to enter the tank, keeping that burner on/off process going.

So, after that initial draw of hot water in the morning, you’ll likely have adequately hot water for the rest of the day.

How you can avoid cold showers in the morning

To help prevent cold morning showers, adjust your water heater’s “temperature adjustment knob."

The temperature adjustment knob controls how far your temperature probe has to expand and contract before the gas burners come on/turn off to heat up your water.

In other words, adjusting this knob makes your thermostat more sensitive to cold water. This means the burners will come on more often and keep your water closer to your set output temperature.

Note: Unless you are familiar with how the temperature adjustment knob works, we suggest having a professional plumber inspect and adjust this. Otherwise, you put yourself at risk of scalding shower temperatures.

Need help from a Florida plumber?

If you are in Florida and need a plumber to inspect your water heater, just contact us. We have locations in Sarasota, Tampa Bay, Orlando, and Naples.

We’ll take a look at your system and give you several options on how you can prevent cold morning showers.

Contact or Schedule a Repair Online!

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