Some signs of a leaky basement are very obvious and others are not so obvious. Of course the most obvious sign of water leaking is water everywhere or pools of water on the floor! You might also actually hear the water dripping or staring at big ugly brown stains spreading across your walls. Sometimes you can even smell the water particularly if it is tainted by sewage or tainted by pesticides. Sometimes leaky water also has the heavy musky smell of fresh soil as often water leaking through a bad basement foundation will also be carrying a lot of silt with it.
There are also lots of other clues that you have a leaky basement. One sign of a leaky basement that is often just interpreted as aging or fading is the presence of efflorescence. Efflorescence is a deposit of a thin white film on your wall. It is the residue left by water that contains minerals and other effluvia from the soil.
Dampness is of course a big sign that you have a leaky basement but you should also look for other signs such as rusting nails or metal fixtures, rotting wood near the floor level, rusted metal feet on appliances, lifted floor tiles and peeling paint. All of these signs are not necessarily indicative of big disaster however it is possibly an indication that your home is suffering some kind of leakage during a rainy or wet season.
Sometimes the leaky basement is not due to some sort of vulnerability in your basement foundation. Sometimes it is caused by breaks in your water supply lines or pipes. Even a small seam or crack in a pipe can cause a big pool of water to form on your basement floor. Yet another big culprit is sinks and toilets that constantly drip as the result of a loose joint or loose pipe. Often this type of water collects beneath a cupboard in which the actual plumbing works are concealed.
There is almost always a little bit of leakage around the places where pipes enter the home. This is because of condensation on the pipes forming dew. To prevent this type of water leaking into your house (and first make sure that it is not the pipe itself that is leaking or your efforts will be futile) you can patch it with a waterproof concrete patch. Keep in mind that this will not prevent the water from forming from behind the walls. The only thing that might prevent that is the installation of a dehumidifier. Dehumidifiers can be an important tool in your battle against basement moisture and molds but not if the moisture is actually due to water seepage as opposed to water condensation.
There is a very easy way to determine if water on your basement walls is due to condensation or seepage. Simply tape a piece of aluminum foil to your basement wall. After a few days inspect its surfaces. If there is moisture on the inside surface that was touching the wall then you are dealing with a leak. If moisture forms on the aluminum foil side that is facing out from the wall then the problem is condensation and can easily be dealt with by a dehumidifier.
The good news is that condensation is a lot easier to manage than leaking water. Although it is persistent the excess humidity is manageable. Exposure to sunlight and wind can help dry out a basement that is dripping with condensation. It is also a good idea to keep basement windows closed if you live in a climate that is overly humid or that has a heavy rainy season.
Learn the causes of a wet basement and how to avoid them at Waterproof a Basement .