"hydraulic effect"

Guest User
Is there any technical information available on the 'hydraulic effect' of water being suctioned uphill between metal panels? Under what conditions does this occur?
David Stermer
Tim, 'Hydraulic effect' is also known as 'Capillary Action'. Wikipedia has an interesting article on Capillary Action. About the only requirements for this to occur in metal roofing are two pieces of metal in close proximity and the presence of liquid water. Two ways that capillary action is commonly defeated are by the use of sealants and anti-siphon grooves. Sealants block the path of water. Anti-siphon grooves are areas in the side lap where the two pieces of material are not in close proximity, defeating the capillary action. In my experience, sealant is the more effective of these two methods for defeating capillary action. Regards, David Stermer

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