Why Is My Tankless Water Heater Running Hot and Cold?

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.