Venting Tankless Hot Water Heaters Through the Roof
If you have a gas tankless water heater and want to vent it through the roof, you can do so in the same way you would vent a gas water heater. The setup requires a length of PVC pipe, an appliance adapter, horizontal drain tee, support clamps and roof cap. You will need an opening to vent through, as well. In most cases, if you are already heating water with gas, the venting system will be in place. All you will have to do is connect it to the tankless heater. Does this Spark an idea?
Instructions
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Connect the adapter for your tankless heater to your heating unit. Each heater has a different adapter, and yours should come with your unit.
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Attach the first leg of vertical pipe to the adapter, and then connect an elbow joint to this section for the horizontal run of pipe.
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Connect your horizontal drain tee fitting to your first section of horizontal pipe, and run the remainder of the horizontal pipe until you are directly below the roof venting hole.
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Connect an elbow joint to the horizontal pipe and then begin to run your vertical pipe up through the roof. You will need to cut a hole into the ceiling and through any rafter boards, then through the roofing boards, if a hole is not already in place. Do this using a hole bit and high speed drill, or a saw with a wood cutting blade.
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Run vertical pipe up through the ceiling until you get to the roof joists. Install a fire stop and support clamp on the first roof rafter, and run your vertical pipe through it. The support clamp attaches to the top of the roof joist and holds the pipe in place.
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Cut a hole large enough for the roof jack, then slide the roof jack through the hole and secure it in place with adhesive. Thread the rest of the vertical length of pipe up through the jack.
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Install a storm collar over the pipe and roof jack. Trim your roof shingles so they slide on top of the collar base, but under the collar flashing. Nail this collar into place using roofing nails or shingle nails.
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Install the proper size rain guard onto the top of your pipe. This rain guard will be sized to the width of your pipe, which most likely will be 2-inch PVC pipe. Attach the rain guard with PVC adhesive.
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Tips & Warnings
A professional is best prepared to properly vent a tankless heater. The do-it-yourselfer could end up damaging the roof, and leaks could occur around the new vent system, wiping out any "savings" you see by completing the job yourself.
