Why Tankless Water Heater Shuts Off During Shower?

Why Tankless Water Heater Shuts Off During Shower?

Unfortunately, some people experience their tankless water heater shutting off during showers., presenting them with an unexpected and uncomfortable cold interruption.

In this article, we will look at the most prevalent reasons of this problem and offer troubleshooting advice to help you resolve it.

Understanding and addressing these shutdowns can guarantee that you have a steady supply of hot water whenever you need it.

Let’s get started and figure out how to maintain your tankless water heater functioning properly.

Common Reasons for Tankless Water Heater Shutdowns

Insufficient water flow:

Low flow rate: To activate and continue heating water, tankless water heaters require a minimum flow rate. If the water flow goes below this level, the device will shut off.


Blockages or limitations in the water pipelines can reduce the flow, leading the tankless water heater to shut down as a safety precaution.

Protection against overheating:

High temperature limit: As a safety measure, tankless water heaters have a high-temperature limit switch. If the water temperature rises over a particular point, the machine automatically shut down to avoid scorching and any damage.

Mineral accumulation or scaling: Minerals can form inside the heat exchanger over time, lowering efficiency and cause overheating. This can cause the high-temperature limit switch to trip, resulting in shutdowns.

Sandwich effect of cold water:

Temperature swings: The cold-water sandwich effect happens when temperature swings occur during a shower. It occurs when hot water is halted for a brief period of time, followed by a blast of cold water before hot water restarts. This can be caused by the tankless water heater’s delayed responsiveness to changing flow rates.

Shower system design: Shower systems with several showerheads or a thermostatic mixing valve might aggravate the cold-water sandwich effect by adding mixing problems.

Ignition problems:

Problems with the gas supply: Tankless water heaters that use gas may experience ignition failure if the gas supply fails. This can involve problems such as low gas pressure, gas line obstructions, or a faulty gas valve.

In the event that the pilot light or ignition component fails to ignite the gas burners, the tankless water heater will not heat the water and may shut down.

Thermometer or Pressure Valve Issue:

Problems with the thermometer:

Incorrect temperature reading: A malfunctioning thermometer may produce false temperature readings, causing the tankless water heater to shut down to prevent water from becoming overly hot or cold. This is a precautionary step to avoid scorching or insufficient hot water.

Problems with pressure valves:

Excessive pressure accumulation: A faulty pressure relief valve may fail to discharge excess pressure within the tankless water heater. This can cause a rise in internal pressure, causing the unit’s safety systems to shut down in order to safeguard against any damage or risks.

Other possible factors:

Power outage: Electric tankless water heaters require a constant power source. Any interruption or fluctuation in electricity might cause the machine to shut off.

Error codes and malfunctions: A variety of faults or error codes displayed on the unit’s display might cause the device to shut down. These problems may need expert diagnosis and repair.

Troubleshooting Tips for Above Problems:

Examine the water flow and pressure:

·         Check that all of the water valves that supply the tankless water heater are fully open.

·         Showerheads, faucets, and water filters that are blocked or obstructed should be cleaned or replaced.

·         Inspect and clean any material or sediment accumulation in the tankless water heater’s water input filter.

Examine the venting system:

·         Check that the vent pipe is correctly installed, clear of obstacles, and vented to the outside.

·         Examine the venting system for evidence of damage or disconnection and repair as necessary.

·         Check to ensure that the vent pipe size is adequate for the device and meets the manufacturer’s standards.

Check the gas supply and pressure:

·         Check that the tankless water heater’s gas supply valve is fully open.

·         Using a manometer, check the gas pressure entering the device. For the proper pressure range, consult the manufacturer’s instructions.

·         If you suspect a problem with your gas supply, contact a skilled technician or your gas utility provider to examine and repair the situation.

Replace the water filter:

·         Inlet water filters on tankless water heaters are frequently blocked with silt or debris over time.

·         Locate the water filter (check the user handbook if necessary) and clean or replace it as directed by the manufacturer.

Problems with the thermometer:

·         Check the temperature setting and make any necessary adjustments.

·         Using a different thermometer, check the accuracy.

·         Contact the manufacturer for assistance or a replacement.

Problems with pressure valves:

·         Inspect and repair a pressure relief valve that is leaking.

·         Manually check the valve for appropriate operation.

·         Check the water pressure and, if required, install a pressure-reducing valve.

·         If you are unsure about an inspection or adjustment, consult an expert.

Check for fault codes and reset the heater:

·         To reset the system, some tankless water heaters offer a reset button or a control panel option.

·         Examine the unit’s display for any error codes or warnings. To understand the codes and take necessary action, see the user manual or the manufacturer’s website.

These are some of the issues and solutions for “Tankless Water Shuts Off During Shower.” I hope my guidance provided you with a solution.


How do I know if my water pump has an airlock?

Symptoms of a water pump airlock:

·         Water flow from faucets is reduced or non-existent.

·         Pump making unusual noises or vibrating.

·         Water supply pressure fluctuations.

·         When faucets are switched on, air sputters or spurts out.

Why does my shower pump keep cutting out?

The shower pump may continue to cut out owing to problems such as a malfunctioning pressure switch, clogged pump filter, system airlocks, or electrical faults. To remedy the frequent pump cut-outs, it is advised that you troubleshoot and address these probable reasons.

What is the average life of a shower pump?

Shower pumps generally have a life expectancy of 8 to 10 years. However, this varies based on a variety of factors such as pump quality, consumption patterns, maintenance, and water conditions. A shower pump’s lifespan may be extended with proper maintenance and frequent service.

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