Septic hydraulic overload?


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Old 05-30-17, 07:29 PM
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Septic hydraulic overload?

I have a 4 bedroom home built in the fall of 2016 in eastern NC. It has a conventional septic system with I believe a 1000 gallon tank and 4 lines in the drainfield.

So, while we were at the beach for 3 days my wife's cat decided to somehow turn the water on to the garden tub. Not sure when he did it but the tub was full of water and the overflow drain was the only thing that saved the house from being flooded. That faucet is capable of 16gpm at 60psi!!! Now, the water was on maybe halfway but it is safe to say that several 1000 gallons of water most likely went into the septic system. Full blast for 72 hours would have been 69000 gallons!! The drainfield is not wet and there have been no issues inside either but I wanted opinions on any problems this may have caused or is there anything I need to be looking out for (besides a huge water bill).

Next time I am turning the water main off coming into the house! Dang cat!
 
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Old 05-31-17, 04:23 AM
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Welcome to the forums!

How deep is your drain field? The odds are everything is ok. While it's likely the extra water may have overwhelmed the field, the ground will soak up the water and return to normal.

I always turn my water off when I expect to be gone for an extended period. No pets in the house but there can't be an unnoticed plumbing leak/break to cause any damage that way.
 
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Old 05-31-17, 04:49 AM
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I once sold the oldest house in Sheffield, circa 1755, and the absentee buyer who bought it was from Laos. He had heard that moving water won't freeze,

While most of us understand that concept meant leaving the water running at a trickle . . . . but his interpretation meant letting it gush like at 20 gallons a minute !

By the time we stopped him. he had ruined a spring that had serviced the property for over 200 years, and his leach field had collapsed from being washed out with no solids being added as replacement.

The well never came back; he had altered the configuration of the water table through his mis-understanding of that simple property of water., and the language used to explain it.

Your new house and its waste water disposal system will probably be just fine.
 
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Old 05-31-17, 05:46 AM
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I don't know how coastal you are but if you're in sandy soil the water could drain away pretty quickly. It may take a while for all that water to soak into the ground and/or evaporate but you should be OK. The soil around the leach field is likely saturated so I would keep your water use in the home to a minimum for as long as possible. The first sign of trouble may be a sewage backup so pay attention to the toilet flushing and keep an eye on the lowest drains in the house, probably a tub.
 
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Old 05-31-17, 06:38 AM
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Thanks for the welcome and responses.

Pilot Dane, we live in Pitt County, so not as sandy as the coastal region but still sandy loam.

Marksr, not sure of the exact depth or the drain lines. They are fairly shallow. My distribution box lid is only 2-3 inches beneath the surface. Already had to replace the lid due to the landscaper driving over it and cracking it while grading the back yard. Only reason we dug it up was it shifted the d box when it happened and all of my effluent was going down one line for the first 6 months. Can't miss the one lush streak of green grass. Luckily, we adjusted the flow diverters before the cat flooded the field.

Can solids still get to the drain lines with the newer systems? Does the filter combined with the baffles in the tank prevent this?
 
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Old 05-31-17, 07:10 AM
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While I don't know much about them - filters are supposed to prevent solids from entering the drain field. With the system being less than a year old the odds are there isn't a big accumulation of solids in the dispersing section of the tank. Today's tanks have 2 or more sections with the bulk of the solids being in the first section [were the sewage enters]

Since your field is shallow and no signs of water above it - that means the ground did a good job of absorbing the excess water.
 
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Old 05-31-17, 09:14 AM
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Under normal operating conditions the septic tank remains at about 85% full and for each new gallon of waste water coming from the house, a gallon exits the septic tank for the drain field (leach field).

Every septic system has a limit to how much waste water can enter each hour. More than that equals hydraulic overload. This limit is based on the absorption speed (perc rate) of the soil of the drain field. If the perc rate is very fast then the overall drain field might be smaller (square feet). If the drain field lines fill up and then the septic tank itself fills up to 100%, then the system will back up into the house possibly causing a floor drain or basement level laundry sink overflow onto the floor. The overflow drain in a sink or in a toilet tank does not help if the drain line down below fills up and overflows.

You were lucky that the cat didn't manage to turn a faucet on so high as to exceed that limit. The guy from Laos was not so lucky. In his system most likely a weak spot developed in the drain field to some low point on the surface and water escaped from there eroding the soil badly over a short period of time.

The drain field is not supposed to need replenishment of solid material. No solid material should be washed out of a drain field. No solid material should come from the septic tank into the drain field.

After an unexpected influx of a large amount of water, the septic system should return to normal after several hours of little or no additional waste water, assuming no damage to the drain field visible from outside.
 

Last edited by AllanJ; 05-31-17 at 09:46 AM.
 

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