Flue Gas Moisture Content

[Patrizia Leones]

Twothoughts one being you live up there with Santa Clause it appears some one has excessive moisture traveling back down the exhaust flue either from condensate in the winter or if there is no 180 degree fitting on the exterior side rainwater could be entering the pipe in any event someone is draining the system before it gets inside the furnace cabinet for what reason I know not

For draining flue gas condensation on a HE unit. Looks site made, which might be OK depending on mfr instructions. The loop is intentional (as Charlie indicates it is a trap). Pay attention to where it drains as the water will be corrosive due to combustion byproducts.

As for a health concern IMHO no CO would get past the loop trap but yes it is a Piss poor way of getting from point A to Point B if properly installed the flue pipe is designed to slant back toward the factory drain hoses within the furnace cabinet and with a 180 degree exterior fitting there should be no rain water to deal with

ChimneySaver Water-Base Water Repellent is a penetrating, V.O.C. compliant, water repellent which contains a proprietary modified siloxane. This water-based siloxane penetrates masonry up to 1/4 inch or more depending on surface porosity and moisture content at the time of application. ChimneySaver Water-Base Water Repellent reacts with the minerals in masonry in the presence of ultraviolet light and atmospheric moisture. This reaction forms strong permanent bonds beneath the surface and creates a hydrophobic zone that prevents water molecules from penetrating, while allowing free migration of water vapors. The chemical bonds formed in this process allow ChimneySaver Water-Base Water Repellent to become an integral part of the substrate and provide long term water repellent protection.

According to the Brick Industry Association, chimneys require special attention and maintenance to prevent costly damage caused by water penetration. Because chimneys project above the roof line, they are vulnerable to the elements. Nearly every chimney you encounter has signs of water damage! The first step is to determine the cause and then find the best corrective measures. ChimneySaver, the first product developed specifically for chimneys, has been used successfully by leading chimney professionals for nearly 20 years. It reduces water penetration into the masonry by 99.9%, according to ASTM tests conducted at the University of Wyoming.

ChimneySaver is a concentration of a proprietary modified polysiloxane which was specifically designed for chimneys. ChimneySaver is the leading water repellent addressing the vapor permeable needs of chimneys and the severe weather conditions to which they are exposed.

Since ChimneySaver is a photo-reactive chemical that does not depend on solids to achieve a water repellent effect, the surface remains vapor permeable. ChimneySaver is composed of 100% active ingredients which physically and chemically react with a surface. After a treated masonry surface has been exposed to ultraviolet light, the electrostatic charge of the surface is reversed to match the electrostatic charge of water. This photo-reactive process allows the treated surface to repel water similar to the way two identical poles of a magnet repel each other.

Most waterproofing agents are actually water sealers, which trap water vapors produced inside the chimney. If this water vapor cannot escape it will condense, freeze and accelerate freeze/thaw damage. Our water repellent does not evaporate or wash out and it consistently outperforms and outlives resins, silicones, acrylics, silanes and siloxanes.

ChimneySaver prevents spalling, stains, chloride attack, freeze/thaw damage, loss of insulation value, deterioration, corrosion, efflorescence, and the damaging effects of acid rain and other waterborne chemicals. The product penetrates and bonds with the surface of concrete, masonry, stucco and other porous materials to provide long lasting water repellent protection even at hairline cracks.

This will allow surface wetting into the first 1/100 of an inch of a treated surface. However, upon examination of a cross section of that surface, it is apparent that there is no deep internal water penetration. For the benefit of comparison, if a portion of a surface is left untreated next to a treated section, the untreated section will appear much darker when wet due to deep water penetration.

Yes. When water penetrates brick, and then freezes, a process of delamination begins. Even though water penetration can effectively be stopped with ChimneySaver, no product can restore delaminated bricks. Therefore, flaking or spalling may occur after treatment as a result of previous water damage. If continued spalling or flaking is noticed a year after the initial treatment, a second treatment may be necessary to insure proper protection.

Yes, but an oil-based primer should be used to compensate for the water repellency. Many paints (especially latex) will not adhere properly to a surface that is water repellent. It is recommended that a test application on an inconspicuous area be done first.

An accidental spill or overspray of ChimneySaver on an asphalt shingle roof will not cause damage to the shingles other than discoloration. Until ChimneySaver dries it may float some asphalts to the surface of light colored shingles, thereby causing dark stains to appear. Stains can be removed with a soft brush using either a water-based degreasing cleaner or a chlorinated scouring powder, though scrubbing the shingles may damage them.

Ventubes are hollow stainless steel cylinders installed in chimneys that provide cross ventilation for large flues. When properly installed, they prevent moisture damage that results from condensation in the large cavities surrounding the flue liners. They do this by allowing up to 85% of the condensation inside of the cavity to escape.

Ventubes prevent moisture damage that results from condensation in the large cavities, or chase areas, surrounding flue liners. Moisture vapor held in large cavity areas often condenses on the inside of outer chimney walls when wall surface temperatures fall below air temperatures.

VenTubes help to prevent the efflorescence, spalling, and freeze/thaw damage that is caused by condensation in these cavity areas. VenTubes can eliminate up to 85% of the moisture that damages chimneys with large chase areas. Easy to install, they solve an often overlooked moisture problem.

Years of field observation indicated that chimneys with large cavities surrounding the liners deteriorate much faster than chimneys built according to the recommendations of the Brick Institute of America (BIA), which recommends one inch of air space between the liner and outer brick.

The furnace flue is the often forgotten part of your chimney and many consumers are surprised when serious problems are found within it. Years of service can take their toll on the flue especially when you consider the extreme conditions the flue typically endures. Here is a brief overview of what your furnace flue must do and the challenges it faces:

Oil Boilers/Furnaces: Oil exhaust has a very high sulfur content, and when combined with moisture forms sulfuric acid which can very quickly damage and destroy most flues. Clay flues will tend to flake apart (called spalling), joints erode, holes form, and serious carbon monoxide problems become much more likely. The moisture itself can come from rainwater entry into an uncapped flue, or the moisture can be a byproduct of combustion in a high efficiency furnace or propane appliance. In the latter case the moisture condenses in the flue before being exhausted outside either due to a cold chimney, infiltration air leaks, or an uninsulated/poorly installed liner. Whatever the source, this moisture/sulfur combination can create havoc in as little as a year. Some furnaces simply MUST have a good quality stainless liner installed to function safely. In one recent case we came across a high efficiency System 2000 oil furnace which was installed without a proper stainless liner (which goes against the installation requirements) and one year later it had destroyed the flue to a point where the furnace would no longer run and posed a serious threat to the occupants of the home. The System 2000 is a GREAT oil system, but must be installed properly. Please consult your local dealer or Energy Kinetics for more information.

Transite asbestos was a common product used to vent gas appliances such as furnaces, boilers, and water heaters in older homes in Minnesota. It was also used for sub-slab ductwork, which I wrote about here: Transite vs. Sub-slab ducts. This material is no longer used because the interior of the vent can deteriorate and flake apart, collapsing in on itself. That, and it contains asbestos. Once the interior of the flue deteriorates it can get blocked, causing hazardous exhaust gases from the appliance to vent back into the home, rather than be carried to the exterior.

The photos below show a transite asbestos chimney flue liner I found during an inspection of a 1955-built home in Columbia Heights. The top of the flue liner had fallen off the chimney, and the interior had collapsed in on itself, causing the water heater to backdraft. This first photo shows what the chimney looked like from the roof.

A quick test of the water heater confirmed that it was backdrafting like crazy. The fix is to leave the transite asbestos material in place, block the openings at the top and bottom of the chimney, and replace the water heater with either an electric unit or a powervent unit that can vent out through the side of the house.

Do you need to do anything if these flues are sitting unused? I have an asbestos flue in my house, but the furnace and water heater are vented elsewhere. Is it ok to let sleeping dogs lie, in this case?

Structure Tech specializes in the moisture testing of buildings for the purpose of determining if there is moisture located behind the exterior wall cladding. A moisture inspection of your property has been requested.

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