Rheem RTEX 18 Tankless Water Heater

Rheem is a leading manufacturer of water heaters. Rheem’s Rtex series represents one of the most popular models on the market today. The Rtex comes in 240 volt electric models. It is one of the highest quality and durable heating components available on the market.
The Rheem RTEX line gets high marks by customers all around the globe for its energy-efficient design and space saving functionality.
Rheem RTEX 18 Specifications
- Model:
- Size:
- Weight:
- Max flow rate:
- Wattage:
- Amperage:
- Recommended Breaker:
- Recommended Wire:
- Voltage:
- Temperature Range:
- Warranty:
- Rheem RTEX 18
- 18.25" x 3.5" x 14.5"
- 14.8 pounds
- 4.4 gallons per minute
- 18 kW
- 75 amps
- 2 x 40 amps
- 8 AWG
- 220-240 volt
- 80°F to 140°F
- 5-year warranty
Product Review
The Reem RTEX 18 is an 18 kW electric tankless water heater with advanced self-modulating technology that provides instant and continuous hot water for multiple applications with two heating chambers.
The water heating system is surprisingly easy to use with an external temperature control knob and display. You can easily adjust the temperature to supply enough hot water for kitchen sinks, bathroom sinks and tubs. It’s fast heating technology that turns 40°F water into 140°F in just 3 minutes.
Self-modulation technology automatically adjusts the electrical power to receive hot water on demand, which will certainly reduce your electricity bill and save you money.
It is specifically designed for indoor loactions and installation is left simple. It is durable device and easy to maintain, you can easily replace the heating element if needed. Two 40 amp circuit breakers are required for both heating element.
Your home should be drawing 200 amperes, as the RTEX 18 will draw about 75 to 80 amperes and other home appliances will also require some amperage, so it won’t work properly with 100 amperes.
The compact and space saving design is easy to fit in the small space. It can be easily mounted on a wall. This unit is quite silent without any disturbing relay noise.
Internal View

Key Features
- Instatnt on-demand limitless hot water
- Automatic heat control technology heats water only when neended.
- Save up to 30% electricity bill compared to traditional water heater
- Easy to control temperature from 80°F to 140°F.
- Durable alloy steel casing and copper immersion heating elements
- Compact and easy to fit unit.
- Long warranty period provided.
Pros
- instant hot water
- compact & durable
- self-modulation
- temperature control knob
- temperature display
- quite silent
Cons
- installation cost is bit high
Safety Instructions
- The Rheem RTEX 18 must be installed in accordance with the instruction manual to obtain efficient high performance.
- Two 40 amps breakers with 6 AWG wire gauge must be used to install an 18 kW unit.
- This unit should not be installed in an area with cold temperatures, it may cause water to freeze inside the unit.
- Install the unit in a safe place and away from children. Do not over-tighten the connections, this may cause internal problems.
- Choose the exact heater temperature as per your water heater requirement to save energy wastage.
Final Words
The Reem RTEX 18 is a very good tankless water heater for average as well as large families. It is specifically designed for housings with 240-volt power supplies. This is a tough instant water heater without any other technical issues. It is highly recommended tankless water heater by experts.
Would you please let us know with comments if you have any questions?
Frequently Asked Questions
First you need the following things:
- 240 volt power supply.
- Two 40 ampearge breakers
- Pair of 8 AWG Wire .
After that you should see the wiring diagram for the Ream RTEX18 included in the box.
For full installation of Ream RTEX 18, you should follow the installation manual included in the box.
You can reset the Rheem tankless water heater by pressing the reset button next to the thermostat.