Rinnai is a well-known brand in the water heaters industry, but like any appliance, their tankless water heaters may encounter problems. However, if your tankless unit turns cold to the touch, know that it’s because the water heater is in a rest position as it only warms water on demand. So, as long as you get a proper supply of hot water, meanwhile, the system runs flawlessly overall, and you have nothing to worry about.

On the contrary, Rinnai tankless water heater owners often face the sudden loss of hot water and start getting cold water from the faucet instead. So, here, we will explore the causes of this problem and provide solutions to help keep your Rinnai tankless water heater running smoothly.

Why Is My Tankless Water Heater Running Cold?

Here are the most commonly known reasons for the Rinnai tankless water heater getting cold and sudden loss of hot water:

  1. Stacks of minerals:

Hard water is a prevalent issue in many areas, and it can lead to stacks of minerals in tankless water heaters which creates a blockage in the heat exchanger, resulting in a sudden drop in water temperature. To prevent this issue, it is essential to have your Rinnai tankless water heater serviced regularly. You can do this yourself or hire a licensed technician who can flush out any mineral buildup in the unit and perform routine maintenance to keep your unit running efficiently.

  1. Inadequate Gas Supply:

Another possible cause of a sudden loss of hot water is an inadequate gas supply. Rinnai tankless water heaters require a certain amount of gas to operate effectively. If the gas supply is insufficient, the water heater may not be able to heat the water properly. Even if you get a gas line extension, you could still deal with fluctuations in the water temperature due to the incorrect size of the gas line.

To resolve this issue, check your gas supply and ensure that your tankless water heater is receiving enough gas. If you are unsure, contact a professional to inspect your unit and make any necessary adjustments.

  1. The water filter needs replacement:

It could be that your water heater’s cold water inlet filter is clogged by all the sediments it has filtered till now. Due to this, you cannot get consistent hot water and the Rinnai tankless water heater goes cold. So, what you can do is replace the inlet filter and then check if the issue is eliminated.

  1. Overheating

An overheating unit can also cause a Rinnai tankless water heater to shut down and go cold. This can happen if the unit lacks airflow or the heat exchanger becomes too hot. If you notice that your unit is overheating, turn off the water heater and contact an authorized plumber. They can inspect your unit and make any necessary repairs.

  1. Broken thermostat:

A broken thermostat could also be the reason why there’s cold water coming through your faucet instead of hot water. Once you replace the thermostat, your Rinnai water heater won’t go cold anymore and you’ll get ample warm water for washing and cleaning.

  1. Cold water sandwich:

In case the water temperature keeps on fluctuating between hot and cold, creating a sandwich, you may have to install the recirculating system to take care of the issue. That way you won’t have to deal with the sudden bursts of cold water in a shower.

Final thoughts:

Now that you know why your Rinnai tankless water heater goes cold and what solutions you can implement, there shouldn’t be any problems. However, keep in mind that for most issues, you’ll need to consult an expert plumber and get help as required.

Moreover, regular maintenance and inspections can help prevent these issues and keep your unit running safely and smoothly. So, pay heed to your Rinnai tankless water heater from time to time and ensure that everything works perfectly to get maximum efficiency and good performance.