Before you call in an expensive waterproofing contractor, you should use this do-it-yourself checklist to see if your water leak problems are caused by something other than poor waterproofing.
Gutters
Inspect and clean your gutter and downspouts. Over time even the best of roofing drainage systems can become blocked or the waterproofing troughs develop holes or breaks at the seams. To test your system, remove any leaves, debris or twigs from all the gutters and downspouts.
Then use a garden hose to run water along the troughs and drains for at least 5-10 minutes to make sure the water is being properly carried away.
Foundation
Inspect the slope of the soil and grounds around your foundation. Make sure that any water runs down and away from the house for at least a distance of 48" to 60". If the water doesn't drain way, it could pool up and run backwards into the house causing water damage and mold problems.
Leaks
Check under your sinks, toilets etc for leaky valves or faucets. Also use a flashlight and trace all the water lines down through the house into the basement or crawlspace. Be certain to check the pipes as the come into the house. Remove any loose dirt or rock to look for drips along the lines. Have any waterproofing structures repaired as needed.
Supply Lines
Check the water supply lines for leaks and drips along their joints. Over time water pipes covers or weatherproofing can rot or deteriorate allowing freezing cold to affect the waterproofing around pipe fittings and elbows. To test for leaks turn off all water in the house, even your icemaker. Read your water meter. Now wait 30-60 minutes and read the meter again. If the meter has changed you have an undetected leak. If you have a leak, you need a plumber not a waterproofing pro.
Basement
Check your basement walls for wetness or seepage. The easy way to do this is to take a 12" piece of aluminum foil and tape it against the surface of the suspect wall. Seal all the edges closed. Now just wait a day or two and check the foil. If is wet on the outside this comes from condensation; if it's wet on the inside this comes from seepage. Check with a waterproofing expert about any seepage.
Rainwater
Test for rainwater problems. If you think that rainwater or water runoff from your property, the street or a neighboring yard is running along the surface and reaching the foundation then you need to grade your property. If it is not a gradin, contact a local waterproofing specialist for a quote.
Check http://www.flexcontracting.com for more details.