Rheem Water Heaters > What You Need to Know Before You Buy

What You Need to Know Before You Buy

Above all, anyone buying a tankless unit needs to think about how they use the water in their home -- during peak water usage times, how many faucets, shower heads, bath tubs, washing machines, dishwashers, and jacuzzis will you be running at once? Tankless water heaters provide endless hot water for up to **two** major applications at a time and up to 3-4 sinks at a time.

Our top models will handle up to two major applications at once, such as a dishwasher and washing machine or two showers running at the same time. The best tankless water heaters will pump out 5-6 gallons per minute, or over 300 gallons per hour - and you never run out. An extra-large capacity 80 gallon tank water heater runs dry in about 15 minutes by comparison.

The trouble with extra-large tank heaters is that whether or not you use the 80 gallons of water stored inside, you pay a high price to keep it hot 24 hours a day. Imagine leaving your car running 24 hours a day!

Once you've settled on a heater that will meet your hot water demands while saving you money, you'll need to carefully consider how it will work within your home.

Gas Tankless Water Heaters

Here are four things you'll need to consider before buying your tankless water heater:

1. Gas sizing information

Take a look at the installation manual of the product you'd like to purchase to see the gas sizing requirements. Call your gas company or professional installer to help determine the proper sizing.

2. Combustion air

Tankless water heaters require combustion air. It's important to understand how combustion air will be delivered to your water heater and how much combustion air is needed. When placed in an unconfined area, combustion air can simply be the air within your home. Confined areas (such as a closet) may require air ducts or additional air inlets. Whenever possible, it is always better to pull combustion air in from outside the home - it is cleaner and will keep your tankless water heater operating at peak performance. Check the installation manual for more information about combustion air requirements.

3. Clearances

Tankless water heater placement is another important factor to consider. Each tankless water heater will have different distance requirements between the heater and other parts of your home, as seen in the example above.

Some of the clearances you'll need to consider are:

- Operable windows, doors and other fresh air openings
- Adjacent walls or tall bushes
- Below gutters, sanitary pipework, eaves or overhangs
- Distance above the ground
- From a gas meter, gas regulator, electrical box or another heater

Check the installation manual to see what your heater requires and whether it will work with your home layout.

4. Venting

All indoor tankless gas water heaters must be vented vertically or horizontally to the outdoors using Category III stainless steel venting material (No other venting material is permitted). RTG-42PV indoor models require 3" stainless steel venting. RTG-74PV and GT-199PV indoor models require 4" stainless steel venting. Venting details, including clearances and diagrams, can be found in the "Use & Care Manual" of Rheem indoor tankless water heaters.

NOTE: Rheem outdoor tankless water heaters do not require venting materials.

When choosing an indoor location, you should consider the shortest venting distance to the outdoors. Consult your professional installer or contact us for maximum venting distances. Rheem offers all necessary venting materials, accessories and expertise to make your tankless water heater installation easy - including horizontal vent kits listed below.

Rheem horizontal vent kit (RTG20003) for RTG-42PV series indoor gas models includes:

• (1) Adapter
• (2) 90 degree elbows
• (1) 12" length vent pipe
• (1) Two-piece 6" - 19" adjustable length pipe
• (1) Two-piece horizontal wall thimble
• (1) 90 degree termination elbow with vent screen
• (1) Pressure relief valve

Rheem horizontal vent kit (RTG20066) for RTG-53DV series indoor gas models includes:

• (1) Adapter
• (1) 90 degree elbows
• (1) Horizontal termination
• (1) 12" length vent pipe
• (1) Pressure relief valve
• (1) 18-AWG, 2 conductor thermostat wire for remote control

Rheem horizontal vent kit (RTG20007) for RTG-74PV and GT-199PV series indoor gas models includes:

• (1) Adapter
• (2) 90 degree elbows
• (1) 12" length vent pipe
• (1) Two-piece 6" - 19" adjustable length pipe
• (1) Two-piece horizontal wall thimble
• (1) 90 degree termination elbow with vent screen
• (1) Pressure relief valve
• (1) 18-AWG, 2-conductor thermostat wire for remote control

The location of your indoor tankless water heater may require additional venting material.

NOTE: CPO recommends that appliances be installed by a licensed professional.