Frequently Asked Questions
Q: What is the difference between 30-gauge, 26-gauge and 24-gauge galvanized pipe?
A: Gauge, often shortened as "GA" indicates the thickness of steel. Lower gauge means thicker steel. Higher gauge number means thinner steel. 26-GA galvanized pipe chimney vent pipe and fittings are thicker than 30-GA, but thinner than 24-GA.
Q: What gauge pipe & fittings are suitable for venting a cast iron boiler?
A: Most manufacturers indicate a minimal thickness as 26-gauge or heavier (24-GA, etc.). Some local codes require 24-gauge for vent sizes 6" and above.
Q: Can 30-gauge galvanized pipe/fittings be used for venting a boiler?
A: No. Only 26-GA and heavier gauge pipe is allowed.
Q: What kind of pipe is it?
A: This is a single-wall, seam-lock (snap-lock) type pipe, commonly called chimney pipe, flue pipe or smoke pipe. It comes factory unlocked for ease of storage and shipment. This pipe requires no special tools for installation and can be cut using metal snips (preferred), grinder or hacksaw.
Q: Which specific applications is single-wall galvanized chimney vent pipe used for?
A: The most common use is for installation of standard efficiency (cast iron type, non-condensing) atmospheric/chimney vented gas or oil boilers in a basement or a boiler room.
NOTE: This pipe is to be used inside the boiler room or basement only and is not suitable for attics, floor/ceiling penetrations or outdoor use:
1) If the boiler is vented through a masonry chimney, the pipe only goes as far as the chimney and connects to the chimney liner if present.
2) If a house does not have a masonry chimney, the installer has two main options, namely - either to run B-Vent (for gas) or L-Vent (for oil) pipe vertically through the floor(s)/ceiling(s) all the way to the roof, or to install a double-wall (or triple-wall - as local code or installation guidelines indicate) stainless steel chimney outside, adjacent to the exterior wall. In both cases, the galvanized chimney vent pipe stays inside the basement/boiler room and is connected to either of the vent pipe types described earlier.
Q: Can Category I galvanized chimney pipe be used for cast iron Power-Vented standard efficiency boilers?
A: No. Unlike Category III vent pipe, galvanized vent pipe is neither seam welded nor does it have any internal gaskets and will therefore leak when the boiler fan engages and pushes out the exhaust gases, making it unsuitable for this purpose. Standard efficiency power-vented boilers must use Category III vent pipe only, such as Z-Vent or Nova-Vent by Z-Flex.
Q: How to properly connect galvanized vent pipe and fittings together and to the boiler/furnace.
A: The crimped end (male) of the pipe or fitting is fully inserted into the non-crimped end (female) of the same, all the way to the rib (groove) on the male side, and the connection is secured with self-drilling screws on at least three sides (i.e. front, left and right). Field practice showed that pre-drilling the holes first works best since this prevents the screw from only penetrating the first layer and pushing on the second steel layer (deforming it in the process and failing to secure) instead of drilling and penetrating the second (inner) layer.
Q: Can you make your own crimp connection on galvanized flue pipe/fitting?
Yes - if it's necessary to crimp an end of the fitting or pipe to convert it to a male end, use a hand crimper tool for sheet metal / galvanized pipe which is suitable for the gauge of pipe/fittings you're using - they are common and are easy to use. Make sure the depth of the crimp is the same as on factory-made crimps.
Q: Which side of the pipe/fitting (male or female) should go towards the chimney first? Does it make a difference?
A: Although neither boiler nor vent pipe manufacturers generally specify this kind of information, the best practice is to install the male end pointing toward the chimney. The reasoning behind this is since Category I appliances are atmospheric-vented, where hot exhaust gases rise or are naturally drawn upward, such configuration would minimize possible leaks.
Q: Do you need any special sealant for sealing the pipe/fitting and other connections?
A: For connecting the galvanized vent pipe to the masonry chimney, furnace cement is commonly used to seal the gap/opening between vent pipe and chimney hole. As for the small pipe and fitting seams, usually, no sealant is needed because the exhaust gases are drawn away from the boiler naturally and if any tiny seams/gaps are present, they will simply leak surrounding air into the chimney, but not from it - however, if the manufacturer or local code requires it, a proper sealant must be used. NOTE: the crimped end of the pipe should not be deformed from the original round shape, so as to minimize gaps - oval or a V-bent shapes are not acceptable.
Q: Can high-temperature aluminum adhesive tape be used to seam the pipe/fitting gaps?
A: Our answer would be No. The exhaust gases from standard efficiency boilers (~ 82% AFUE) are too hot and would dry the adhesive quickly, rendering the tape useless. Moreover, due to the nature of atmospherically vented (Cat I) appliances, sealing the small gaps would not provide any benefit as explained in a previous question. Important - if the manufacturer or local code requires the seams to be sealed, these instructions should supersede our recommendations.
Q: Can galvanized pipe be used for wood stoves?
A: No.
