Takagi Tankless Water Heater No Hot Water

Takagi Tankless Water Heater No Hot Water [7 Easy Solutions]

Get no water out of my Takagi Tankless Water Heater! It’s a common complaint of every homeowner I often find on different forums or subreddit .  

Generally, a tankless water heater produces no hot water due to the following reasons: 

  • Unit receives insufficient electric power supply
  • Insufficient gas supply
  • Undersized gas line
  • Cross plumbing
  • Improper gas supply pressure
  • Too low setpoint 
  • Ignition failure

You will get no hot water out of the unit unless you address and solve the issues I mentioned. 

Fortunately, this troubleshooting guide is exactly what you need to fix the no hot water issue and get hot water from your water heater. 

So, without further ado, let’s jump into the guideline to discover the solutions. 

Table of Contents

Takagi Tankless Water Heater No Hot Water [7 Easy Solutions]

This chapter will reveal all the 7 possible culprits behind no hot water problem. Plus, you can find solutions to those issues.

1. Unit Gets Insufficient Power Supply

Takagi Tankless Water Heater requires a 120VAC, 60hz electric power supply. In short, you need to plug your water heater into an electrical outlet that delivers that amount of power. 

If the unit doesn’t receive the electric power it needs for operation, you can’t turn on the unit. So, how can you expect the water heater to heat the water when you can’t even power on the unit? 

How To Fix: 

Ensure you plug the unit into a dedicated electrical outlet that supplies 120Vac of electric supply to your water heater. 

Also, make sure the electric outlet is functional. You can easily check if the outlet is fine or not by plugging another appliance into the outlet. If the appliance you plug into works, it’s okay. 

If the unit is not getting sufficient electric supply power, I highly recommend you call a certified electrician. 

2. Not Getting Enough Gas Supply

For proper combustion, your tankless water heater requires a continuous flow of gas at the unit, gas meter, and gas tank.  

If the unit doesn’t receive a sufficient amount of gas supply, it’s not possible to ignite the burner. And ignition means no hot water. 

Generally, opening the gas valve partially or a bad regulator are the culprits I blame most if you get insufficient gas supply at the unit, gas meter, and gas tank. 

How To Fix: 

Inspect the gas valve position on the gas line first. Make sure you open it fully, not partially. If it’s not fully opened, just turn it counterclockwise. The gas valve should be in line on the gas line. 

Don’t forget to check the gas regulator as well. If it’s bad, enough gas will not flow in the burner chamber. In this case, you need to replace the gas regulator. It will be better to call a professional to inspect the regulator and make the replacement if needed. 

3. Undersized Gas Line

This is, by far, the most common water heater problem responsible for not delivering enough hot water. It’s because most of us have the tendency to connect the existing gas line to the system, which is actually ½” in diameter. 

But my fellow homeowners, you must pay attention to the strict gas line requirements. You should size up the gas pipe according to the following charts- depending on the type of water heater. 

Takagi Natural gas supply piping
*Takagi Natural gas supply piping*
Takagi Propane supply piping
*Takagi Propane supply piping*

How To Fix: 

It’s recommended to size the gas pipe appropriately to get the necessary volume of gas needed for the water heater using the ANSI Z223.1/NFPA 54 in the USA or B149.1 in Canada or local codes. 

It will be best to install the water heater by a certified plumber, who set up the gas lines according to the manufacturer guidelines. 

Otherwise, you will get limited flow capabilities and output temperatures, like getting no or lukewarm water out of the unit. 

4. Cross Plumbing

Getting no or not enough hot water! If it’s the issue you encounter with your Takagi Tankless Water Heater, cross plumbing is what I suspect. 

Cross plumbing is a common water heater problem. It allows unplanned flow of hot water or cold water. In simple words, the hot water flows into the cold water system or the reverse. 

When cross plumbing is your problem, you will observe the following signs: 

  • No or not enough hot water
  • Cold water feels warm
  • Temperature fluctuate 

Several reasons like mixed up hot and cold water lines, bad check valve, or missing check valve are responsible for cross plumbing. 

How To Fix: 

First off, check both the cold water and hot water lines. If there is a cross plumbing between them, correct the water lines. 

Next, ensure the check valve you installed is working properly. On the other hand, if you have not installed a check valve yet, install one to fix this issue. 

The best bait is- hire a plumber to fix the cross plumbing issue if you are not handy in this workflow. 

5. Insufficient Gas Supply Pressure

On a proper functioning water heater, the minimum and maximum inlet gas supply pressure should be: 

Gas TypeMinimum PressureMaximum Pressure
Natural4.0″ W.C.10.5″ W.C. 
Propane8.0″ W.C.14.0″ W.C.

If the gas pressure goes out of range, it will affect your water heater performance. For example, you will get no hot water out of the unit as a side-effect.  

How To Fix: 

Without testing, you can’t blindly say whether the gas pressure is within the specifications or not. Complete the below steps to check the gas pressure: 

  • Set the gas valve on the gas line to the off position. 
  • Locate the pressure port on the gas inlet of the water heater and remove the screw from the pressure port. 
  • Attach the manometer to the pressure port and ensure you set the manometer to zero. 
  • Open the gas valve again and make sure there is no leak. 
  • Turn on the unit and open all the hot water faucets. Don’t forget to press the Max button on the control board. All these will help you operate the unit at maximum rate. Now, take the reading and note it. If the gas pressure exceeds the maximum pressure specification, understand the gas flow gets restricted due to undersized gas lines or supply regulators. 
  • Now, measure the gas pressure at minimum water heater operation. If the pressure is not within the minimum specification, I bet there is an issue. 

I highly suggest hiring a qualified plumber to fix the problem if the gas pressure goes out of range. 

6. Set The Temperature Too Low

It happens often after performing the routine maintenance workflow. If you set the water temperature too low, you will not get desired water temperature output. 

Fortunately, you can easily fix this issue by adjusting the temperature. I already wrote an article on Takagi Tankless Water Heater Temperature Adjustment

You can check that article if you don’t know how to change the temperature on Takagi. 

7. Ignition Failure

If your Takagi water heater has failed to ignite the burner, you will get no hot water out of the unit. Several reasons are responsible for the ignition issue, including: 

  • Tripped hi-limit switch
  • Improper gas supply pressure 
  • Dirty flame sensor
  • Igniter issues

The water heater will pop up the error code 111 on the controller display when ignition failure occurs. 

How To Fix: 

I wrote a detailed guide on ignition failure or Takagi Water Heater Error Code 111. In that article, I broke down everything you need to know to fix the ignition issue. So, it’s worth checking the article. 


Nothing more than frustrating if you get no hot water out of your Takagi Tankless Water Heater.  Luckily, I mentioned all the possible culprits behind this issue and broke down the problems as well. 

Just follow our troubleshooting tips and resolve the issue. If it seems challenging for you to troubleshoot your water heater, don’t hesitate to call a plumber for help. Good Luck!

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