Menu

Call This Saturday to Get $50 Off Any service over $500

Call This Saturday to Get

$

50

Off
Any service over $500

Need an Emergency Plumber? Call

844-444-5855

Financing Available (Subject to Credit Approval)

Book Online Book Now
Why Is My Tankless Water Heater Running Hot and Cold?
4.9 RATING
4.6 RATING
4.6 RATING
Why Is My Tankless Water Heater Running Hot and Cold?
Oct 24,2024

Why Is My Tankless Water Heater Running Hot and Cold?

Tankless water heaters are energy efficient and provide endless hot water on demand. However, you may experience an issue where the water temperature fluctuates, running hot and cold unexpectedly. This is a frustrating scenario, especially when you’re in the middle of a shower or washing dishes. If you notice this problem with your tankless unit, Rooter Man is the go-to plumbing service for repairs. Let’s explore the common reasons this happens, and solutions.

blogdetail-image

Water Flow Rate Issues

One of the most common reasons for temperature fluctuations in a tankless water heater is a water flow rate problem. Tankless systems don’t require a high flow rate to activate and maintain the heating process. If the flow rate decreases below the limit, the heater may shut off temporarily, causing the water to go cold. To resolve this, ensure you’re using enough hot water to maintain a steady flow. In case of a recurrence, hire a professional for water heater repair services, ensuring minimum flow settings without risking further damage.

Cold Water Sandwich Effect

The “cold water sandwich” is a common occurrence that happens when hot water that’s stored in the pipes is used first, followed by a brief surge of cold water before the heater catches up to deliver more hot water. This can cause fluctuating temperatures, especially during short-duration uses like hand washing. You can minimize this by allowing the hot water to run for a bit before use, especially when using fixtures for short periods. It is also advisable to hire a plumber to install a recirculation pump, ensuring you maintain a more consistent supply of hot water.

Mineral Build-up

Hard water contains high levels of minerals like calcium and magnesium, which can cause scaling inside your tankless system. These mineral deposits accumulate and restrict water flow, causing uneven heating or temperature drops. The buildup can interfere with the heating elements, resulting in malfunctions and premature water heater replacement emergencies.

The best way to prevent this is through regular maintenance by a plumbing service provider. Professionals can descale your water heater or install a water softener to minimize mineral accumulation.

Gas Supply Problems

If you have a gas-powered tankless water heater, inconsistent gas supply can lead to hot and cold water fluctuations. Check if your heater isn’t getting enough gas and call a plumber to maintain a steady temperature. This could be because of low gas pressure, a malfunctioning gas valve, or an issue with the gas line. If you prefer a more hands-off approach, contact a professional to check your gas supply and system. Gas issues can be dangerous, so this isn’t something to troubleshoot on your own.

Incorrect Heater Size

Sometimes, the issue is the tankless water heater size. A unit that’s too small for your household’s needs may require more frequent maintenance calls, as it tries to keep up with multiple appliances or fixtures that demand hot water simultaneously. To fix this, you might need to schedule a complete water heater replacement or limit the number of hot water appliances used at once. If you upgrade your tankless unit and experience the same issue, consult a plumbing repair service to inspect and address underlying issues quickly.

Experiencing hot and cold fluctuations with a tankless water heater is frustrating. However, the underlying causes are often easy to identify and resolve. Whether it’s a problem with the water flow rate, mineral buildup, or an undersized heater, a reputable plumbing repair service can address the root issue and restore consistent water temperatures. Contact us at Rooter Man and schedule exceptional water heater repair services to ensure your unit operates efficiently and reliably.

Latest Blog

Smelly Yard? How to Tell If Your Septic Tank Is the Cause Oct 09,2025
Smelly Yard? How to Tell If Your Septic Tank Is the Cause

A foul smell emanating from your drains and the backyard often indicates a severe underlying plumbing problem that requires immediate attention. While there are many possible causes, such as full…

Read More
How Sump Pump Installation Protects Your Foundation and Home Value Oct 09,2025
How Sump Pump Installation Protects Your Foundation and Home Value

Nothing is more frustrating than walking into a basement only to find a flood. Whether it is from snowmelt, heavy rains, or a leaking pipe, water in the basement and…

Read More
Tap vs. Filtered: Why More Families Are Choosing Water Filtration Oct 02,2025
Tap vs. Filtered: Why More Families Are Choosing Water Filtration

Access to safe drinking water is crucial to staying healthy. If you want to keep your loved ones safe, deciding whether to drink tap water or filtered water requires careful…

Read More
How a Professional Septic Installation Saves You Long-Term Costs Oct 01,2025
How a Professional Septic Installation Saves You Long-Term Costs

Septic tank installation is a vital step for property owners without a municipal sewer line connection. Whether you live on the outskirts of a city or are moving to the…

Read More