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Why does my tankless hot water heater go cold?


continuous hot water, anode rod, more money

Nothing feels better than a long hot shower on a chilly Alaskan winter morning. A warm shower also relaxes after a long day at work, regardless of the weather conditions or season in Fairbanks, AK.

When your water heater starts to produce lukewarm water, it can leave you annoyed. It might not affect your shower, but it will affect your washing machine, dishwasher, and kitchen sink.

If your water heater is starting to give you cold water, don’t hesitate to take action. Find out why the temperature on your tankless water heaters fluctuates before you can troubleshoot it.

Here’s why electric water heaters get cold in a few minutes after being powered on. We’ll also give you some practical tips on ensuring your electric water heaters don’t fail. But first, let’s understand how an electric water heater works.

How tankless water heaters work

To understand why a tankless water heater isn’t working efficiently, you must understand how tankless units work. Here’s how it works:

  • A user turns on the hot water tap.
  • The water gets into the heater.
  • The water flow is detected.
  • A computer automatically ignites a burner.
  • Water circulates in the exchanger.
  • The heat exchanger warms the water to the set temperature.
  • The unit shuts off when the tap is shut off.

If you’re well acquainted with tank-style water heaters, you understand they heat water and keep it hot until it’s used.

The average tank-style water heater can store 30–50 gallons of water, which explains why the system is so big. However, despite their reliability, they’re undesirable as they unnecessarily waste a lot of electric (gas) energy by heating water that might go to waste. Unfortunately, these energy losses can significantly inflate your monthly energy bills.

Tankless water heaters, on the other hand, are energy efficient and save you money. Since they don’t store any water, they heat it promptly, making it much smaller than tank-style heaters.

Tankless water heaters are instant units used on demand as they only produce water when needed. The appliance’s flame only kindles the heat exchanger when you switch on the water outlet. The water then enters the inlet pipe from the bottom of the system, and the unit heats the water as it moves via the heat exchanger. Ultimately, the user gets hot water from the pipes.

Top reasons why your Tankless Hot Water Heater Goes Cold

Plumbing crossover

Plumbing issues are a major cause of temperature fluctuations, and an improperly done crossover is a good example. Unfortunately, a single-level faucet, a faulty mixing valve, and compromised plumbing are the main reasons behind this problem.

It leads to the fraternization of hot and cold water, lowering the water temperature. That’s why the Prospector Plumbing and Heating team will always examine your plumbing crossover to ensure the water temperature doesn’t drop.

To know whether you’ve got a plumbing crossover, turn on all the hot water taps and turn off all other outlets. If the water is still running after 10–15 minutes, you’ve got a plumbing crossover problem. Fortunately, it’s easy to repair a plumbing crossover as you only need to inspect your mixing valve or change its cartilage.

Unfortunately, transitioning the cartilage might not fix the problem. You might have to buy high-quality cartilage or faucets to eliminate this issue.

Low water pressure

Low water pressure is among the main reasons tankless water heaters get cold as you shower. The flow in your water heater is lower than the flow rate required to activate the system, which shuts off the gas burner or fails to ignite at all costs.

Only your main gas burner will shut down if your water heater system has a standing pilot. For that reason, check the user manual on the minimum pressure needed, usually around 1 kg per cm2 (10 m of head).

Blocked heat exchanger

If there’s hard water in your residence or you’re using borehole water, then mineral buildup is to blame for your water getting cold. The accumulation of hard water minerals like magnesium and calcium corrodes your pipes and destroys the heat exchanger, leaving you with cold water.

Besides that, avoid using a blocked heat exchanger, as it can be hazardous. To avoid mineral buildup and limescale, consider flushing your water heater frequently. If the heat pump has already accumulated a lot of minerals, consider contacting Prospector Plumbing to help you clean the lines.

Signs that the water heater is broken

Whether you use electric or gas water heaters, there are a few tell-tale signs to help you know when they’re broken.

Not enough hot water

If your water heater barely has enough water, it might be damaged. Fortunately, you can easily fix the issue by adjusting the water heater’s temperature or checking your circuit breaker to ensure your electric water heater is properly receiving power. If that doesn’t work, drain the water storage tank and remove the sediment buildup to improve the efficiency of your heat pump.

Varying water temperature issues

Is your water heater dispensing hot water at one moment and cold water at the next moment? Most people ignore these fluctuations, which indicate a bigger water heater problem. To fix that, ensure the thermostat on your water heater is well set or call a technician from Prospector Plumbing to check for damaged internal water heater parts.

Concerning sounds when the water heater is turned on

Loud cracks, bangs, whining, pops, or boiling sounds indicate something is wrong when your electric or gas water heater is turned on. When that happens, your first action should be to drain the tank and remove the residue. However, you may need a residential water heater replacement in severe cases, so call a professional technician immediately.

Looking for professional plumbing and heating technicians to fix your residential water heater? Prospector Plumbing is here for you!

Prospector Plumbing is a professional full-service maintenance and repair company helping residents in Fairbanks, AK, fix water heaters and other household equipment. We understand different houses’ heating and plumbing needs, and our crew is always eager to offer long-lasting solutions regardless of your energy source. Call (907) 322-5763 to schedule an appointment today!