Without a doubt, chimneys are the most susceptible masonry surface on your entire home to damage from water. Freeze-thaw damage is magnified since the chimney projects so high above the roof line. There is no shelter for the chimney, so taking steps to prevent damage before you are faced with pricey repairs is absolutely necessary. The Brick Industry Association states that chimneys require special attention and maintenance for such prevention, and ChimneySaver Solvent Base Water Repellent is formulated specifically to battle the elements chimneys face.
This water repellent has been used by professionals in the chimney business for almost twenty years due to its special formula. The aspect that 
sets apart this water repellent from the rest is the fact that it is a vapor permeable formula. It will not trap water vapors that are always present in the brick, like other sealants. If the water vapors are trapped inside the brick, as they expand and contract due to freezing and thawing, the face of the brick is likely to pop off or cracks will occur. The formula, although vapor permeable, will still fully protect the brick from water damage. According to ASTM tests run at the University of Wyoming, it reduces water penetration into the brick by 99.9%.
ChimneySaver Water Base Water Repellent is another version of ChimneySaver water repellent. This water repellent is specially formulated for brick that has never been treated by other sealants before. Although still effective on surfaces that have been previously treated, its formula is based with water and works to maximum efficiency on surfaces that have never been treated. The Solvent Base Water Repellent is recommended for surfaces that have been previously treated. Due to its mineral spirit base, it will effectively penetrate brick that has been treated in the past, although it will also work on brick that has never been treated at all. Either one of ChimneySaver’s Water Repellents are each formed specifically to prevent the deterioration of your brick on the chimney, meaning it is the most durable formula on the market.
Expect for the product to cover approximately 90-150 sq. ft. per gallon. It is available in 3, 5, 30, and 55 gallon containers giving you flexibility that matches the size of your project. You must apply ChimneySaver Solvent Base Water Repellent in temperatures above 40 degrees Fahrenheit, and allow at least two hours of drying time. There must be a six hour window of time between application and any rainfall. The recommended application is with a pump sprayer, and cleanup is easy requiring only soap and water.