Hundreds of communities throughout the United States are already experiencing flood conditions, which can cause extensive water damage to homes and businesses.

Flood conditions can also cause sewage from sanitary sewer lines to back up into houses and businesses through drain pipes. These backups not only cause damage that is difficult and expensive to repair, but can also create health hazards.

Most homeowners and business insurance policies do not cover sewer backup unless specific coverage is added to the policy, according to the Insurance Information Institute.

Flood damage is not covered, either under a sewer backup policy or a standard homeowners, renters or business policy. Flood coverage, however, is available in the form of a separate policy both from the National Flood Insurance Program and from a few private insurers.

Causes of sewer backup

* Blockage due to tree roots. Shrubs and trees seeking moisture can make their way into sewer line cracks causing extensive damage. They may start out small, getting into a small crack in the pipe. But as the tree or shrub continues to grow, so does the root. Tree roots can enter the service pipe at joints and cause blockages. They can also travel a long way, and roots from different types of trees act differently. If you suspect that city trees are responsible for sewer line damage, your plumber can contact the city and samples of the roots will be used to help identify the trees and thus, who is responsible for cleanup. Sometimes, a blockage is the result of a combination of city and private trees. In this case, costs are split between the city and property owner.

* Sanitary main. A blockage can occur in a city sanitary main. If the blockage is not detected in time, sewage from the main can back up into homes and businesses through floor drains. Usually this happens slowly, giving the owner time to call a licensed plumber to assess the damage. If water is entering your basement at a rapid rate, call the city public works office and report the problem immediately, so that a city operator can investigate.

* Water in basement. Most basement flooding is not related to the sanitary sewer system. In many cases, soil settles adjacent to the building and, if not corrected, leads to rainwater flowing toward the buildings where cracks may have developed in the foundation or floor slab that allow water to enter the basement. The cement floor and basement walls of these structures may have deteriorated to the point that they are no longer waterproof. Thus, water can show up in a basement that has never had a water problem. This frequently happens when the ground is saturated after repeated or heavy rain storms. Drainage can be improved by making sure that water drains away from the building. Homeowners can also prevent flooding by water-sealing the basement.

How to prevent backups in your lateral and in the city main

* Dispose of grease properly. Cooking oil should be poured into a heat-resistant container and disposed of properly, not in the drain, after it cools off. Washing grease down the drain with hot water can cause significant problems. As the grease cools off, it will solidify either in the drain, in the property owner's line or in the main sewer causing the line to constrict and eventually clog.

* Dispose of paper products properly. Paper towels, disposable diapers and feminine products can cause many problems in the property owner's lateral as well as in the city main because they do not deteriorate quickly as bathroom tissue does.

* Replace your line with new plastic pipe. One way to prevent tree roots from entering your line is to replace your line and tap with new plastic pipe. If you still have problems with tree roots growing in your lateral, you may have to have roots cut periodically.

* Do not use illegal plumbing connections. Do not connect French drains, sump pumps and other flood control systems to your sanitary sewer. It is illegal and debris and silt will clog your line. Consult a plumber to correct any illegal connections.

* Install a backwater prevention valve. A backwater valve is a fixture installed into a sewer line and sometimes into a drain line in the basement of your home or business, that prevents sewer backflows. A properly installed and maintained backwater valve allows sewage to go out, but not to come back in. Property owners are responsible for the installation and maintenance of backwater valves. The cost to install one depends on the type of plumbing in your home or business and the difficulty of installation. Check with a qualified plumber.

What to do if you experience a sewer backup

A sewer backup can lead to disease, destruction of your valuables, damage to your house or business and can result in electrical malfunctions. Prompt cleanup of the affected property can help minimize the inconvenience and prevent mold and further damage. In the event of sewer backup, immediately arrange for the cleanup of your property. This should include:

* Wet-vacuuming or removing spillage,

* Mopping floors and wiping walls with soap and disinfectant,

* Flushing out and disinfecting plumbing fixtures,

* Steam cleaning or removing wet carpets or drapes,

* Repairing or removing damaged wallboard or wall covering, and

* Cleaning up ductwork.

How to file a claim

For insurance claim purposes, take before-and-after photos of the affected areas and itemize any property losses. Save all receipts related to repairs, cleaning or damages and contact your insurance agent or company representative as soon as possible. There may be a separate deductible that applies with this coverage, depending on the state where you live, so check with your insurer.