Septic Tank Problems When it Rains

Updated February 21, 2017

Rural communities know firsthand the problems associated with excessive rainwater and septic tank systems. The septic tank itself is a uniquely self sufficient mechanism that allows the accumulation of massive amounts of waste to naturally process without routine maintenance, however septic tanks do encounter problems. Parking or driving over septic tanks can cause major shifting problems, but heavy rains can do even more underground damage to these tanks.

Essential Functions and Rainfall

Septic tanks function as an extremely small version of a sewage treatment facility that usually are used by those communities with no access to government or local drainage lines. Drain fields are essential to septic systems. Examples are peat moss, stone fibre plant beds and small ponds. Excess amounts of rainfall can saturate the drain fields enough to cause the system to back up into the basements of houses or seep through the foundation or housing of the septic tank. Older septic tank systems commonly encounter this problem after heavy rain.

Septic Tank Shifting

Rich and secure soil beds are essential to septic tanks to ensure that they stay firmly in one place. Over time the weight of the tank and natural shifting of the earth can cause the septic tanks to move. Heavy rainfall over areas where septic tanks are stored can oversaturate soil around the septic tank, causing the tank system to shift and possibly break free from piping running from the building or house that is connected to the septic system. This is a costly problem for septic tank owners who live in areas with heavy annual rainfall.

Septic Tank Water Overload

During heavier rainfalls the septic tank may be bombarded with such a large torrent of water that the rainwater may start to enter the system. This can occur with above or below ground septic tank systems. If cracks in piping are present or major seals are worn and loose then rainwater will eventually start to fill up in the tank and cause it to overload and eventually it will fail. Routinely checking the piping and seals of the tank may help prevent this problem from occurring.

Saturated Leach Fields

Septic tank leach fields are usually checked for proper drainage and soil absorption prior to installing tanks. Heavy rainfall over older leach fields may result in environmental hazards simply because the amount of water in the field may not be able to be absorbed as fast during heavier rain. This can cause wastewater to rise to the surface and be dispersed over the ground, causing a smelly and toxic mess and a potentially costly problem to clean. Heavy rains cannot always be predicted, so this problem may occur at times for any septic system, but normally this is associated with older systems.

Rain Gutters and Drainage

Rain gutters and external drains of the home should be placed so they do not deliver any rainwater runoff to the septic field. The average home, during a rainstorm that delivers about an inch of water per hour, can have a runoff of over 50,000 gallons of water. If this water is delivered directly into the septic field it will quickly fail, especially in heavy downpours and could either back up the system into the house or lift wastewater out of the soil, causing environmental havoc and extremely costly repairs.

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