29 Dec

4 Common Problems with Tankless Water Heaters


The vast majority of people who switch to a tankless water heater for their home are delighted with their decision. There’s a lot to like about going tankless, including lower energy bills, unlimited hot water, and longer service life. However, there is no such thing as a “perfect” home appliance, and tankless systems can experience a few mechanical or maintenance challenges. 

Tankless Water Heater Installation

Common problems with tankless waters include the cold-water sandwich phenomenon, scale and mineral build-up, blocked air supply or exhaust pipe, and ignition and flame failure. Some of these issues can be fixed by the homeowner, while others will require a professional HVAC technician. 

1. Cold-water sandwich

The dreaded cold-water sandwich occurs when the water coming out of a faucet goes from warm to cold then back to warm. This can be an unpleasant experience, especially when you’re taking a shower. The phenomenon happens when a hot water outlet is used twice in a row. Some warm water will still be in the pipe from the first usage, followed by cold water. Then there will be a delay until the second round of hot water reaches the faucet, resulting in the uncomfortable sandwich. 

The easy solution is to let the water run a bit until the cold sandwich passes. You can also have a recirculating system installed that prevents cold water from sitting inside of pipes. 

2. Scale and mineral build-up

You may be aware that hard minerals such as calcium and magnesium can collect inside a tank water heater, eventually leading to corrosion. However, minerals can also impact your tankless water heater, even though the water quickly passes through and is not stored in the system. Scale can cling to the inside of the tankless unit, which can hurt its performance and shorten its service life. 

To remove mineral deposits, you can periodically descale and flush your tankless water heater with vinegar or a specialized descaling kit. If you have hard water, you could install a water softener system to balance minerals from the water supply before it enters the tankless water heater.

3. Error code for blocked air supply or exhaust

Natural gas water heaters need proper t air flow for combustion and venting. If there’s an inconsistency, your unit may give you an error code indicating an air supply or exhaust issue. Most tankless water heaters are direct-vented, which means there will be two horizontal PVC pipes running from the unit to an exterior wall. Go outside and make sure there isn’t any debris stuck in these pipes. If you clean out the air supply and exhaust pipes yet still get the error message, contact an HVAC professional.

4. Ignition or flame failure

If you have a problem with ignition or the flame for gas tankless water heaters, you won’t have much (or any) hot water. There could be a wide range of explanations for these issues, including a stuck gas valve, failed regulator, or lack of gas (either natural gas or propane). If other gas appliances seem to be working in your home, it’s a good idea to bring in an HVAC technician to troubleshoot the issue. 

Expert tankless water heater service

If you experience any of these common tankless water heaters, call the experienced team a Robert B. Payne, Inc. Addressing issues as quick as possible is key to keeping your water temperature comfortable and your energy bills low. Schedule an appointment today at (540) 373-5876.