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TWIN PIPE VENTING GUIDE
Determine Installation Location
Environment
Air surrounding the water heater, venting, and vent termination(s)
is used for combustion and must be free of any compounds that
cause corrosion of internal components. These include corrosive
compounds that are found in aerosol sprays, detergents, bleach-
es, cleaning solvents, oil based paints/varnishes, and refrigerants.
The air in beauty shops, dry cleaning stores, photo processing
labs, and storage areas for pool supplies often contains these
compounds. Therefore it is recommended that outdoor models be
used for these locations where possible.
The water heater, venting, and vent termination(s) should not be
installed in any areas where the air may contain these corrosive
compounds. If it is necessary for a water heater to be located in
areas which may contain corrosive compounds, the following in-
structions are strongly recommended.
IMPORTANT CONSIDERATIONS:
• DO NOT install in areas where air for combustion can be con-
taminated with chemicals.
• Before installation, consider where air has the ability to travel
within the building to the water heater.
• Where possible, install the water heater in a sealed closet so
that it is protected from the potential of contaminated indoor air.
• Chemicals that are corrosive in nature should not be stored or
used near the water heater.
• Locate the vent outlet where flue gases will not harm surround-
ing plants and/or cooling equipment. All vent locations must ad-
here to the recommended vent/combustion air intake terminal
position as outlined in Table 3.
• Avoid locating vent where prevailing winds could affect the perfor-
mance of the water heater or cause recirculation of the flue gases.
• DO NOT terminate the venting over a public walkway or over
an area where condensate or vapor can create a nuisance / haz-
ard or where condensate can be detrimental to the operation of
equipment such as regulators or relief valves.
• Water Heater flue gases must be piped from the appliance to
the outside, installer MUST adhere to the instructions provided
herein and the most recent Water Heater Manual and all appli-
cable codes.
• The exhaust and combustion air must terminate through the
same sidewall or roof as the terminations must be in the same
pressure zone and face the same direction.
• The vent pipe must terminate either through the sidewall or
through the roof, exhaust/vent termination and/or intake air
openings shall adhere to clearances as set forth in the Direct
Vent Termination Clearances diagram.
• Each Condensing Tankless Water Heater requires a separate
vent system.
• If common venting is required, refer to common Vent Installa-
tion Manual (latest revision) for instructions on optional venting
method as well as to verify which tankless models may be com-
mon vented.
• Use only PVC/CPVC three (3) inch (7.6 cm) and four (4) inch
(10.2 cm) Venting.
Damage and repair due to corrosive compounds in the air is not
covered by warranty.
For PVC/CPVC vent systems reduce the maximum allowable length
for each elbow and termination type as follows and as referenced
in Tables 11-14 of this document:
Exhaust and Combustion Air Intake Pipe Diameters and Max
Lengths:
• For PVC/CPVC vent systems reduce the maximum allowable
length for each elbow and termination type as follows:
* 2.5 feet (76.2 cm) for every 45° elbow.
* 5 feet (1.5 m) for every 90° elbow.
* Termination.
• Exhaust and combustion air intake pipe diameters to be as spec-
ified in Tables 11-14 of this document.
• Do not exceed exhaust and combustion air intake pipe MAXI-
MUM lengths as outlined in Tables 11-14 of this document.
(Lengths are specific to models and fuel type).
Additional Clearance Requirements:
• Avoid termination locations near a dryer vent.
• Avoid termination locations near commercial cooking exhaust.
• Install vent termination at least twelve (12) inches (30.5 cm)
above grade or anticipated snow level.
Vents shall not terminate:
• Over public walkways; or near soffit vents or crawl space vents
or other area where condensate or vapor could create a nuisance
or hazard or cause property damage.
• Where condensate or vapor could cause damage or could be
detrimental to the operation of regulators, relief valves, or other
equipment.
Important considerations for locating vent termination under a
soffit (ventilated or unventilated or eave vent; or to a deck or
porch):
• DO NOT install vent termination under a soffit vent such that
exhaust can enter the soffit vent.
• Install vent termination such that exhaust and rising moisture
will not collect under eaves. Discoloration to the exterior of the
building could occur if installed too close.
• DO NOT install the vent termination too close under the soffit
where it could present recirculation of exhaust gases back into
the combustion air intake part of the termination.
Determining Vent Length
There are two options for determining the vent lengths/compo-
nents necessary for the installation.
Option 1: The installer can use the vent length calculation sheet,
filling in the quantity of the vent components in order
to calculate the total equivalent vent lengths.
Option 2: The installer can use the maximum vent length tables
on the next pages to determine the amount of straight
pipe that can be used with a specific termination type
and quantity of elbows.
15
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