Venting Requirements For
Gas Tankless Water Heaters
In general, the tankless water heater should be
installed where the vent length is as short and straight as
possible. The exceptions to the short distance would be the Bosch 38B,
125B, 1000P, 1600H, 1600P and the 125HX which have a minimum vent
length of 6 feet. If you live in a warm (non-freezing) area than you
have the option of installing the Bosch 250SXO, 125BO and 2400EO
models and the Rheem RTG53X and RTG74X models outside with no need
for venting. Otherwise the units are designed for an indoor
installation with exhaust venting.
- Bosch 38B, 1000P Models: Vented vertically
(through roof) only. Use 4" diameter type B (double
wall) vent - 6' minimum vertical height.
- Bosch 125B, 125HX, 1600H, 1600P Models: Vented
vertically (through roof) only. Use 5" diameter type B
(double wall) vent - 6' minimum vertical height.
- Bosch 125FX Models : Vented horizontally
(through wall) only. Use 4" dedicated, sealed, single
wall vent (stainless steel or 26+ gauge galvanized). 15'
maximum run with two elbows - must terminate horizontally.
FXHOOD required.
- Bosch 250SX, 2400E Models
: Can be vented vertically or horizontally. 3" diameter dedicated, sealed, single wall vent (stainless steel). 26' maximum run with one elbow - subtract 2.5' for each elbow. Please see our 3”
Venting Guide
- Rheem RTG-53 Models
: Can be vented vertically or horizontally. 3" diameter dedicated, sealed, single wall vent (stainless steel). 34' maximum run with one elbow - subtract 1.5' for each elbow. Please see our 3”
Venting Guide
- Rheem RTG-74, GT-199 Models: Can be vented
vertically or horizontally. 4" diameter dedicated,
sealed, single wall vent (stainless steel). 47'
maximum run with one elbow - subtract 5' for each elbow.
Important Factors to Consider
Gas Venting Requirements
Gas Line Sizing Requirements
Gas Combustion Air Requirements
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