Whenever there is more water outside than inside a floodwall, levee or building, water continually tries to get inside. Obvious paths of intrusion are sewer drains for the bathtub and toilet and drainage tubes in flood walls and levees. Floor drains in some areas of buildings also could provide such a path. Any channel with its inside opening below flood level must be blocked. The channels may not be obvious - such as an air-conditioning condensate drain - so look carefully.
More on using valves, plugs, caps and seepage barriers.
If you protect a building with a floodwall, sealant, plastic wrap or any other barrier, you will need to pump water during floods. Rainwater that falls inside the flood barrier or water that seeps under the barrier must be pumped to the outside. Water that comes in through leaks in the barrier or around gates and other closures also must be pumped out. You can reduce seepage and leakage with careful design, construction and maintenance, but water will get in. Your flood protection system should include an area (a sump) where water can collect and be pumped out before it causes damage.
More on choosing and using pumps.
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