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Is Your Home’s Water Running Hot and Then Cold? Here’s What Might Be Going On

If your water temperature keeps fluctuating between scalding hot and icy cold, you’re not alone. Many homeowners experience inconsistent water temperatures, especially when running showers, dishwashers, or faucets. 

Not only is this annoying, but it can also signal a bigger issue lurking within your plumbing system. Let’s dive into some common causes behind water temperature swings, what you can do to troubleshoot them, and when it’s time to call in the professionals.

Common Reasons Your Water Temperature Is Inconsistent

1. Water Heater Problems

Your water heater is the most obvious culprit. Whether you have a tank or tankless model, several issues can affect its performance:

  • Sediment Build-Up: Over time, minerals from hard water collect at the bottom of a traditional tank water heater, reducing its heating efficiency.
  • Failing Heating Elements: In electric units, heating elements can wear out and cause temperature drops.
  • Thermostat Issues: If the thermostat isn’t calibrated properly or is malfunctioning, the temperature will vary.
  • Tank Size Matters: If your water heater is too small for your household’s needs, you’ll run out of hot water faster—especially during peak usage times.

2. Cross-Connection Plumbing Issues

A cross-connection occurs when hot and cold water lines are improperly connected or if a fixture is backfeeding into the system. This can happen with faulty mixing valves or poorly installed plumbing fixtures. When this happens, cold water can infiltrate hot water lines (and vice versa), leading to dramatic swings in temperature.

3. Faulty Mixing Valves or Shower Valves

In many homes, especially older ones, mixing valves inside faucets and showerheads help regulate the blend of hot and cold water. If one of these valves becomes worn out or blocked with debris, the temperature can shift unexpectedly while you’re using water.

4. Pressure Imbalances

Have you ever experienced the infamous “shower surprise” when someone flushes a toilet or starts a washing machine? That’s a pressure imbalance. When cold water is diverted elsewhere in the house, less is available at your shower valve, causing the water to spike in temperature temporarily.

5. Issues With Tankless Water Heaters

Tankless systems can be extremely efficient, but they’re sensitive to flow rate. If water demand exceeds capacity or if filters are clogged, the unit might struggle to maintain consistent temperature, especially in multi-fixture use.

Troubleshooting Temperature Fluctuations

Before calling a professional, there are a few things you can check on your own:

  • Inspect your water heater’s thermostat and ensure it’s set to an appropriate temperature (generally 120°F is recommended).
  • Flush your water heater to remove any sediment buildup, especially if it hasn’t been done in over a year.
  • Check for visible leaks or corrosion around the water heater, which can indicate internal damage.
  • Note when the issue happens—if it’s only when multiple fixtures are used, it could point to pressure or sizing issues.

When to Call a Plumbing Professional

If you’ve gone through basic troubleshooting and the issue persists—or if you notice signs of more serious problems like:

  • Rusty or discolored water
  • A leaking water heater
  • Water that runs out quickly despite a large tank
  • Consistent temperature swings in multiple locations

…it’s time to call in one of our licensed plumbers.

Contact Potter Heating Cooling & Plumbing today to schedule your plumbing services. Our team is here to help with all of your heating and air conditioning needs.

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