3 Reasons Why the Hot Water’s Too Hot in Your Home

A hot shower

Hot water’s great for coffee, not baths.

Scalding hot tap water is dangerous, especially for children and seniors. 120 degrees Fahrenheit is the safety recommendation against scalding baths, but 140 degrees is the default setting on most water heaters.

Even 120 degrees is too warm for baths; anything over 111.2 degrees puts people and pets at risk. Steam from the bathwater or shower indicates you should turn it down a notch.

That seems easy enough — mix cold water with hot to prepare your bath. Problem solved, right?

Well, maybe, and maybe not. Because:

  • Water that’s too hot from the tap is still a problem for young children and some seniors, who may not have the awareness to mix in cold water.
  • Too-hot water is a waste — energy and money waste. You’re paying for excess heat.
  • Too-hot water can be due to a faulty hot water thermostat that needs replacement.
  • A malfunctioning water heater can burst! 69% of water heater failures result from a slow leak or sudden burst. Both problems can cause severe water damage; a bursting water heater is every bit as hazardous as it sounds.

Why the Water’s Too Hot

Now that you understand the gravity of the problem and have resolved to do something about it, a little DIY troubleshooting should put you on the path to safety.

We’ve determined that a water heater temperature setting, faulty thermostat, or malfunctioning water are the most likely reasons for too-hot water. Let’s go through the steps for each.

1. The Temperature Setting on Your Water Heater Is Too High

Most experts agree that standing water below 120 degrees can be a breeding ground for bacteria like legionella (which causes Legionnaire’s disease).

So 120 degrees is your water heater’s ideal temperature setting — warm enough to keep bacteria at bay and cool enough to prevent most scalding injuries.

Unfortunately, most water heaters have less-than-helpful low-to-high dials that don’t indicate exact temperatures, although they offer a scalding warning.

You may have to make a series of adjustments, measuring the water temperature at the tap in your bathroom each time to get it right.

2. High Mineral Content in Water Contributes to Heater Malfunction

Minerals in water can settle to the bottom of a tank as sediment, collect on a water heater’s heating element, and make the heater go cattywampus. Among other things, it will overheat.

This problem has an easy fix: flush your water heater, or have a plumber do it for you as part of your annual plumbing checkup.

Some cities have notoriously hard water (high in minerals), including most cities in California. If sediment in your hot water tank is a recurring issue, you may need to install a water softener to reduce mineral content.

3. You May Have a Faulty Water Heater Thermostat

If you’ve turned down the temperature dial on your water heater, flushed any sediment, and yet water temperatures remain too high, you may have a faulty thermostat.

We don’t recommend thermostat replacement as a DIY repair unless you’re incredibly handy, but we’ll take you through the steps.

How to Replace a Gas Water Heater Thermostat

The thermostat is part of the gas valve component in gas water heaters. You can’t replace a thermostat separately from this piece.

Natural gas is explosive and toxic. Even a small leak can be deadly, so again, we advise you to call a certified plumber or appliance repair technician for the job we’re outlining below.

  1. Locate the gas valve.
  2. Your water heater should list model information. Use this to look up the correct thermostat replacement parts — or you can find a universal valve and thermostat.
  3. Shut off the gas.
  4. Turn off the gas line to the water heater, ensuring the valve is perpendicular to your gas line. Remember that this is different from your gas valve on/off switch.
  5. Wait for the water to cool. It may take a few hours.
  6. Unhook the lines that connect to your gas valve. These may include the gas line, thermocouple, pilot light supply line, and main burner supply line. Depending on your model, you may also have an electronic igniter to unhook.
  7. Replace the gas valve per the manufacturer’s instructions.
  8. Make sure you get a tight fit! Anything less invites a gas leak. Teflon tape may help to secure the connection.
  9. Refill your water tank.
  10. Close your drain valve and turn on the water supply. You can close the pressure relief valve once some water drains and open a hot water faucet to release the air from the tank and lines.
  11. Re-install the lines that connect to your gas valve.
  12. Set the gas valve to off. Then, after you’ve tightened everything, check for leaks. Turn on the gas line to your water heater; apply soapy water to the gas valve. A leak will cause more bubbles to form.
  13. Finally, you can light the pilot. Your new gas valve should have instructions to help you through these steps.

Not up for this job? Call Orange Coast Plumbing! We guarantee your satisfaction and warrant all repairs.



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