A flooding basement when there are no rain or storms present means one thing — something is wrong with your plumbing system. Knowing what to do can help prevent major damages from becoming worse.
Diagnosing the Cause
There are three likely causes if a plumbing leak is flooding your basement. The first is a backed-up sewer drain. It's generally obvious when this is the cause since there are both the odor of raw sewage and the murky brown water that indicates that the leak is from wastewater.
A second likely cause is the hot water heater. If it bursts or if pressure in the heater triggers the overflow valve, then many gallons of water can flood your basement. This water will be clear and possibly hot. There will also be no hot water from any of the taps if the water heater is to blame.
Finally, the third thing most likely to cause flooding is a water line leak. This could be a leak from a water main coming into the home, a secondary line that runs through the basement, or an appliance or faucet in the basement. You may be able to trace the leak to its sources, such as a broken washing machine line or supply line running through the ceiling. The water from the leak should be clear, and any attached taps or appliances won't be able to receive water.
The first step is to mitigate damage. If there is any chance that the flood line will rise high enough to affect wall outlets or electrical appliances that you can't move, then you need to shut off power to the basement. You can do this at the circuit breaker so only the basement is powerless. Doing so lowers the risk of shock or an electrical fire.
Once it is safe to enter the basement, locate the water main and turn it off so that no more water flows into your home to cause more flood damage. You can turn off the main, or you can turn off the valve that controls the appliance that is leaking such as what would be the case with a leaking water heater.
Raw sewage poses a health hazard. If it is a small amount, you can clean it up with towels and bleach, but you should wear gloves and face protection so the sewage doesn't come in contact with your skin. Clear water is much easier to clean up. Doing so quickly is important to prevent mold and water damage. Use fans to dry the area quickly.
The final step is to contact a plumbing service in your area if you encounter a plumbing emergency in your basement. They can fix the cause of the leak so your drains work properly again.