Venting Requirements; Maximum Equivalent Lengths; Minimum Equivalent Lengths; Maximum Number Of Elbows - A.O. Smith 101 Series Instruction Manual

Venting reQuirements

approVed materials
Approved vent and intake air pipe materials that may be used in
the United States:
• PVC Schedule 40 (ASTm D 2241 / CSA B181.2, ASTm D
1785 / CSA B137.3
• CPVC Schedule 40 (ASTm F-411 / CSA B137.6)
• ABS (ASTm D-2661)
Approved vent and intake air pipe materials that must be used
in Canada:
• ULC S636 PVC / CPVC
field supplied fittings
Field supplied fittings should be equivalent to the piping material
being installed. Field installed/supplied fittings will add equivalent
feet to the vent or intake air piping as indicated below. All field
supplied/installed fittings and piping must be factored into the
equivalent feet calculations.
• 90° elbows (short or long radius) are equivalent to 5 linear
feet (152 cm) of pipe.
• 45° elbows (short or long radius) are equivalent to 2.5 linear
feet (76 cm) of pipe.
primer and cement
Tetrahydrofuran (THF) primer should be used to prepare the
surfaces of pipe and fittings for solvent welding. if CPVC or ABS
pipe and fittings are used, then the proper cement must be used
for all joints, including joining the pipe to the factory provided
terminations (PVC material). PVC materials should use ASTm
D-2564 Grade Cement; CPVC materials should use ASTm F-493
Grade Cement and ABS materials should use ASTm D-2235
Grade Cement.
pipe siZe reQuirements
The water heaters covered in this manual are certified for the use
of 4 and 6 inch pipe for the vent (exhaust) and intake air piping.
if the installed equivalent length for the intake air or vent piping
will be 70 feet (21.3 m) or less, 4 inch pipe must be used. if the
installed equivalent length will be more than 70 feet (21.3 m), 6
inch pipe must be used.
note: install the pipe size required for the installed equivalent
length of each pipe independently. iE: if the intake air pipe will
be 70 equivalent feet or less and the vent pipe will more than 70
equivalent feet; the intake air pipe must be installed using 4 inch
pipe and the vent must be installed using 6 inch pipe.

maximum eQuiValent lengths

four inch pipe
The water heaters covered in this manual are certified to
a maximum length of 4 inch pipe for the exhaust venting
arrangement of 70 equivalent feet (21.3 m). The certified
maximum length of 4 inch pipe for intake air piping is also 70
equivalent feet (21.3 m). iE: On Direct Vent installations both
pipes can be up to 70 equivalent feet (21.3 m).
six inch pipe
The water heaters covered in this manual are certified to
a maximum length of 6 inch pipe for the exhaust venting
arrangement of 120 equivalent feet (36.5 m). The certified
maximum length of 6 inch pipe for intake air piping is also 120
equivalent feet (36.5 m). iE: On Direct Vent installations both
pipes can be up to 120 equivalent feet (36.5 m).
intake air and Vent pipe clearances
The minimum clearance from combustible materials for the vent
(exhaust) and intake air piping shall be 0 inches. Vent or intake
air piping passing through a combustible wall or ceiling must be
a continuous run (no joints).

minimum eQuiValent lengths

four inch pipe
The water heaters covered in this manual are certified to
a minimum length of 4 inch pipe for the vent (exhaust) of 15
equivalent feet (4.6 m). There is no minimum equivalent feet
requirement for the intake air pipe.
six inch pipe
The water heaters covered in this manual are certified to
a minimum length of 6 inch pipe for the vent (exhaust) of 70
equivalent feet (21.3 m). There is no minimum equivalent feet
requirement for the intake air pipe.

maximum numBer of elBows

The vent pipe may have a maximum of six 90° elbows installed.
The intake air pipe may have a maximum of six 90° elbows
installed. iE: in a Direct Vent configuration each pipe can have up
to six (6) 90° elbows installed. Two (2) 45° elbows equal one (1)
90° elbow. Each 90° elbow is equivalent to 5 feet (1.5 m) of linear
pipe, 45° elbows are equivalent to 2.5 feet (0.75 m) of linear pipe.
factory supplied fittings
The water heater ships with two (2) factory supplied 4 inch
terminations (PVC 45° elbows with debris screen). Factory
supplied vent and intake air terminations or concentric
terminations must be used. Factory supplied terminations and
installed fittings (exhaust elbow and intake air connection) add
zero equivalent feet to the vent and intake air piping.
note: 3 inch intake air and/or vent terminations previously
installed on older BTH 300/400 model installations must be
replaced with factory supplied 4 inch or 6 inch terminations
depending on the installed length.
taBle 7
number of 4 inch pipe
90° elbows
maximum feet (meters)
installed
One (1) 65 feet (19.8 meters)
Two (2) 60 feet (18.2 meters)
Three (3) 55 feet (16.8 meters)
Four (4) 50 feet (15.2 meters)
Five (5) 45 feet (13.7 meters)
Six (6) 40 feet (12.2 meters)
6 inch extended Vent terminations
When 6 inch intake air or vent pipe is installed using standard
terminations, factory supplied 6 inch terminations must be used.
Contact your local distributor or call the parts department (phone
number listed on the back cover of this manual) to order 6 inch
termination(s).
optional concentric terminations
BTH 300 models installed using 4 inch vent/intake air piping
use the 4 inch concentric termination. BTH 300 models installed
using 6 inch vent/intake air piping use the 6 inch concentric
termination. BTH 400 and 500 models must use the 6 inch
concentric termination on all installations.
Contact your local distributor or call the parts department phone
number listed on the back cover of this manual to order.
• 4" Concentric Termination Part # 9006328005
• 6" Concentric Termination Part # 9006144005
22
6 inch pipe
maximum feet (meters)
115 feet (35.0 meters)
110 feet (33.5 meters)
105 feet (32.0 meters)
100 feet (30.5 meters)
95 feet (29.0 meters)
90 feet (27.4 meters)