The most serious effect of a failing system is the potential for serious disease from the leaking and improperly treated waste.

Dysentery and hepatitis can be spread by these wastes.

In addition to the diseases themselves, mosquitoes and flies that spread some illnesses can breed in areas where liquid waste reaches the surface.

Chemical or nutrient poisoning can also be a problem.

Many of the synthetic products you use around the house, such as strong cleaning products, can be poisonous to humans, pets and wildlife if they travel through soil to your well or on the surface to lakes, streams or ponds.

Excess nitrate levels in drinking water can pose serious health threats to infants. The health of plants around your home can be seriously affected, too.

The waste from failing systems can kill many species or cause increased growth of undesirable plants.

The economic costs of failure are no less important. The most obvious effect is the direct expense of replacing your septic system. This could cost $2,000 to $4,000.

Also consider the indirect cost of losing the use of your house while the system isn't working and the long-term inconvenience of a system that doesn't operate properly.