Secret Septic Tank

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liquid-kool

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I have owned my home for 5 years. Last week I had my septic inspected and drained for the 2nd time since I purchased the home. To my surprise the technician dug up and and drained a second septic tank. It was completely buried with the exception of one small part that I assumed was part of the first tank. The first tank is 1500 gallons, the second is 1000 gallons. I am concerned about this second tank, I can't imagine needing two tanks. The fact that it was completely buried makes me think it was defective, or for some other reason abandoned and purposely buried. Anyone have any experiences like this?
 
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fixitron

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The most common reason for 2 tanks is for the first to overflow into the second and then the effluent is pumped to a leach field. Most septic tanks are 1,000 gal. What is a "mart"?
 

liquid-kool

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The most common reason for 2 tanks is for the first to overflow into the second and then the effluent is pumped to a leach field. Most septic tanks are 1,000 gal. What is a "mart"?
Sorry, mart was my fat fingers... should have ready 'one small part'.
So why would the second tank be buired? It was deep.. the cover is only 5 feet from the first but yet it is 2-3 feet deeper into the ground.
 

fixitron

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So the second tank was taking overflow from the first tank? If there is a pump in the second tank, it usually has a vent pipe to above ground. The pump would be to pump the effluent to a leaching field,, either because the field is higher than the tanks or the designer wants to dose the field with hundreds of gallons at a time, rather than trickling a couple of gallons for each use of water in the house. Dosing will use all of the field while trickling will only use the nearest part.
This begs the question- where is your leach field? Is it a conventional system or engineered?
Septic systems require a licensed engineer design and drawings, which should be on file with your local government.
 

chiraldude

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When I bought my previous house, the drainfield failed inspection so a new field was added. Because the old tank was not up to code, it was also necessary to put in a new tank. The contractor decided to connect the new tank to the old tank in series. He said it adds some extra protection from solids getting to the drainfield. Maybe this is what happened to your property? I believe it is a common practice.
Last year the new tank started backing up so I had it pumped. I also had the old tank pumped and found that there were no observable solids accumulated in it.
If your second (small) tank is in fact set up this way and there were no solids in it, you can call it your "just in case" tank and should never need to have it pumped again.
Were you able to get a camera in the smaller tank? You would have been able to see where the inlet and outlet baffles were located. Good to know for future reference if you have other issues.
Sadly, it is rare for home owners to have drawings and/or pictures of the septic layout so people like yourself are left to guess and speculate on what is going on underground.
 

fixitron

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Usually, a septic tank is located within 10 ft. of a house, so as to eliminate the need for a coupling (DWV pipes come in 10 ft. lengths), which would probably make it difficult to install a new tank between the old one and the house.
 

Jeff Hardie

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You said it was inspected and pumped. You should of received a report and explanation. Please do not let these guys keep coming out and pumping your septic system every couple of years and not give you a diagnostic of why your system is failing. You should not have to pump out your tanks at all if the system is working. That's a another discussion on how to maintain your system.

First tank will be your sludge or solids tank. 18" or 2' lower then your inlet will be the outlet that goes to the second tank. Because the outlet is a couple feet down from the inlet only the liquids travel to the second tank. The solids float to the top in the first tank and form a sludge layer. This sludge layer builds thicker and thicker and can block your inlet flow from the house causing a back up. The inlet port of the tank should have a baffle or Tee that keeps the sludge layer at bay.
 

Hugh

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I have owned my home for 5 years. Last week I had my septic inspected and drained for the 2nd time since I purchased the home. To my surprise the technician dug up and and drained a second septic tank. It was completely buried with the exception of one small part that I assumed was part of the first tank. The first tank is 1500 gallons, the second is 1000 gallons. I am concerned about this second tank, I can't imagine needing two tanks. The fact that it was completely buried makes me think it was defective, or for some other reason abandoned and purposely buried. Anyone have any experiences like this?
It could also be that tank #1 is for anaerobic action, and tank #2 is for aerobic. Does the second tank have any aeration--a motor, or a pipe that pumps in air from somewhere?

I have a jet aerator system, but the two tanks together total 1000 gallons. You have to dig up the first tank's lid, but the second is above ground so you can access the motor/aerator.
 

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