We've all heard the story about the little Dutch boy who saved Holland by plugging a leaking dike with his finger. While a finger can be a good immediate water plug, there would be a tulip shortage and far fewer Dutch people if little boys' fingers had become widely accepted as the best material for repairing leaks in dikes.
Hydraulic cement is a lot like the Dutch boy's finger plug. It's cheap, simple and can be applied quickly. The results are sometimes immediate - the leak is usually stopped, disaster is averted. The problem is that too many people believe that since hydraulic cement is an inexpensive leak stopper, it's the right material for every repair.
In many manholes, the cause for leaks can be traced to movement. As a manhole settles, the walls and the floor can crack. Seals around lateral pipes and joints are stressed and begin to fail. When the water table rises and subsides, every crack, failed seal and loose joint is subjected to pressure and flexing. As water migrates through these openings, it carries in surrounding soil and fill material forming voids outside the manhole. This accelerates the deterioration because the manhole structure is free to shift and move.
Because hydraulic cement is a rigid surface patching material, it can't tolerate movement. When stressed by movement, it cracks, crumbles and delaminates. Then, the leaks are back. The real solution for problem leaks in manholes is injecting a flexible repair material like Prime-Flex 900 LVSF. It reacts with water to form a tough, flexible, watertight foam. It cures inside the crack and seals all the way through fractures, separated joints or failed seals. It retains flexibility, so if the structure moves, the Prime-Flex 900 LVSF moves with it. It also fills voids that surround the manhole, helping to stabilize the structure.
While Prime-Flex 900 LVSF costs a little more than hydraulic cement, it saves money in the long run. When you add the hours spent patching and re-patching the same leak with hydraulic cement, you realize how expensive a cheap fix is. You might have saved money by hiring a little Dutch boy to stop leaks with his finger.
