Correcting the problem must absolutely be done from the outside. It is impossible to correct the problem permanently from the inside. The water is on the outside and by sealing the outside you prevent further entry. If the sealing is done from the inside, where the water is able to enter in the block and under the basement floor, it will eventually break through to the basement. The problem, therefore, has returned as has the water in your basement. In other words, lock the barn door before the horse is gone, not afterwards.
Attempting to waterproof from the inside, after water has already invaded your basement, creates another problem. In this process, new drain tile is laid along the inside of the footers. A connection is then made to the sump pump, thereby disregarding the original drainage system (installed outside the walls) and the connection to the storm sewer. As gravity drainage must be accomplished wherever possible, this process is clearly wrong. Now, looking at this logically, if laying the tile inside had been considered a better and superior way, wouldn't the plumbing code and city ordinance regulate this in the initial construction of buildings? Why don't they? The answer is that it is the function of the storm sewer to carry the water from the downspout and drain tile to a point of disposal, not through the walls and into the basement and then out again.
When there is a storm which brings heavy rainfall, the city main storm sewer may be unable to handle the amount of water, thus forcing the water to back up toward the house. This does not create a problem as long as the drain tiles are on the outside of the wall of a properly waterproofed basement. A serious problem arises, however, when the tiles are laid inside the basement and the water backs up and sits underneath the basement floor because the storm sewer is overloaded, the sump pump is malfunctioning or the electricity has been lost. Eventually the water table will rise and force the water into the basement.
Don't overlook the sealing of the wall. The foundation must have protective coatings to prevent further entry of water. What good does it do to seal the wall from the inside after the water has already entered and is fully able to saturate it? The purpose of coating externally is to prevent this from happening.
Another risk is taken when the drain tiles are installed inside the basement along the side perimeter and are connected to the sump pump. Some companies drill holes (approximately 1.5" to 2.5" in diameter) through the wall just above the footers allowing the water to enter and be diverted to the sump pump. It is clearly logical, that this weakens the original wall. Drilling holes through the wall is an easy solution, but results in eventual disaster. In other words, more holes only mean more leaks in the future. This is just like the old Dutch fable in which Peter stops the leak in the dike with his finger. These situations both result in eventual disaster. I recommend the opposite: seal the cracks and holes that are already there and make your basement watertight.
Comparing waterproofing contractors should be done with care. Do not choose a contractor who exposes his unprofessionalism by using scare tactics. No reputable waterproofer will try to force you to sign a job that you aren't certain you want or need. Indeed, reputable contractors have an abundance of work and will not offer a "special deal" that must be accepted on the spot.
Beware of lifetime guarantees which may expire long before you think. They are meaningless if the company offering them folds. The best guarantee is receiving quality service and workmanship.
Also beware of those who would insist that what you need is a sump pump. If a foundation is properly waterproofed from the outside, and your home is not situated atop a geyser, a sump pump is not the proper solution. In a heavy rainstorm, when the electricity goes off, an electric sump pump will be of no use at all.
Be suspicious of people who claim to have x-ray vision. Waterproofing problems occur below the ground, out of sight of those of us who are not Clark Kent. If someone tells you that he knows exactly what your water problem is and what to do to solve the problem without testing, cleaning or exploring, then he is wasting his unusual talent along with your time and money!
While periodic maintenance of drains and sewer lines can be a desirable thing to undertake to prevent problems, don't be sold a bill of goods by a door-to-door salesman who is out only for his commission and is master of the hard sell. A damp or leaky basement or drain clog problem is not the end of the world. Take your time and use good judgment when deciding what to do about these problems.
Leaky basements should not be puzzling to the consumer, neither should the septic system. The drainage system is where all problems begin. For this reason, the drainage system should be properly cleaned and maintained.
