Once you have found an electric tankless water heater that matches your needs and can handle the winter temperature demands of your locale, you are ready to begin installing. Aside from a simple circuit tester and a pipe cutter, the only tools you need are those already in your toolbox.
To install a tankless water heater - If you are sure that your breaker panel has adequate power and space for additional breakers, you are ready to begin by throwing the main breaker into the off position. Remove the cover and use a circuit tester to double check that the power is off.
Insert the new breakers with the same brand as the panel. Your user’s manual will specify amperage of breakers for the model heater you are installing. This is usually two or three 40-amp breakers, depending on the model.
Using the type wire specified in in the manual, attach a pair of wires into each breaker and secure the ground wire to the ground bar. Repeat this for each breaker. Be sure not to cut any stands when removing insulation. Remove no more insulation than necessary, usually about ½ inch.
String wire to the tankless heater and attach wires as shown in the manual diagram.
Start by opening all the faucets and turning off the water where it enters the house, to drain the system.
Next tape fittings to the pipes where you want to join in to the existing system. Work toward the tank from this point by measuring and cutting pipes.
Installing you own plumbing comes with two options: The traditional method is to “sweat” pipe connections, using a torch, lead-free solder and flux. A plumbing how-to book can show you the technique for doing this.
The second method is very simple but costs more. This is the use of compression fittings to join pipes together. All it takes is to a cut a pipe to length and force into the fitting with a twisting motion, just like a Tinker Toy set.
Be sure to include hot and cold cut off valves in your new water lines and use several wraps of plumbers tape anywhere you have threaded pipes, to prevent leaks. You may want to use lengths of threaded flexi pipe for the final connection to the heater to make the final connection easier.
The last plumbing step is to cut the old systems pipes where you taped the fitting and join up the tankless heater with the existing water system.
The final step is to flush the water system and avoid vapor lock. With the breakers still off, turn the main water line on and then turn off all the faucets but one. A shower would be best for this. Now turn the breakers on and adjust the temperature knob and hot water cut off valve to find the hot water temperature that is right for you.
You are now ready to enjoy hot water from your new electric tankless water heater.
Your county or municipal area may have codes regarding installing anything that requires electrical or plumping skills. Electrical tankless heaters have high power demand and may require a breaker panel upgrade.
If you ignore signs that an aging tank is failing, you could risk flooding.
To find out what size tankless hot water you need go to this site.