Septic Tank Tee's

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Arky217

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Four questions on septic tank tees.

My newly installed concrete septic tank is 56" tall overall; it does not have any interior walls or baffles.
The top and bottom are 4" thick.
The inside height from floor to ceiling is 48".

The bottom of the 4" inlet hole is 41" from the floor.
The top of the 4" inlet hole is 3" from the ceiling.

The bottom of the 4" outlet hole is 39.5" from the floor.
The top of the 4" outlet hole is 4.5" from the ceiling.

Now for the questions:

1) Should the top of the inlet tee be open or closed and why ?

2) Should the top of the outlet tee be open or closed and why ?

3) How far down from the bottom of the inlet hole should the tee extend and why ?

4) How far down from the bottom of the outlet hole should the tee extend and why ?

Thanks,
Arky
 

Smooky

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You should be able to find most of the answers here starting on page 38

http://www.healthy.arkansas.gov/aboutADH/RulesRegs/OnsiteWastewaterSystems.pdf

I cut and pasted a section from the code below:



11.6.4. Tank proportions. The liquid depth of any tank compartment shall not be less than 36 inches and shall not exceed 72 inches. The minimum horizontal distance from the inlet to the outlet of any tank may not be less than 72 inches. Storage capacity is required above the liquid line to provide for that portion of scum that floats above the liquid in all septic tanks. On the average, 30% of the total scum will accumulate above the liquid line. In addition to the provision for scum storage, one inch shall be provided at the top of the tank to permit the free passage of gas back to the inlet and house vent pipe. For tanks having vertical sides, the distance between the inside top of the tank and the liquid level shall be 12.5% of the liquid capacity or 9 inches, whichever is greater. In horizontal, cylindrical tanks, this distance should be equal to 20% of the tank diameter.


11.6.5. Inlet and outlet. Four-inch or larger sanitary tees shall be used as inlet and outlet devices in all septic tanks. The septic tank manufacturer shall provide properly constructed inlet and outlet devices with each tank. The effluent line leaving the tank shall be Schedule 40 PVC. The inlet invert shall enter the tank at least 3 inches above the liquid level in the tank to allow for a momentary rise in liquid level during discharges to the tank. This free drop prevents black water and standing of solid material in the house sewer leading to the tank. The inlet tee shall extend at least 6 inches below the liquid level in the tank and extend above the liquid level to a minimum of one inch from the top of the tank. In no case shall the inlet device be greater in length than the outlet device.


11.6.5.1. Outlet tees shall extend to a distance below the surface 35 to 45%of the liquid depth.

11.6.6. Approved outlet filters are recommended on all septic tanks. Outlet filters have been shown to reduce total suspended solids (TSS) and biochemical oxygen demand (BOD) and should be utilized to protect and lengthen the life of the absorption area. Proprietary gas deflectors designed to deflect or otherwise prevent solids from entering the outlet tee are not required but are recommended to increase the efficiency of the septic tank. Where gas deflectors, outlet filters, or other devices requiring routine maintenance are installed in the tank, a service riser extending to grade shall be installed over the outlet inspection port.
 

Arky217

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You should be able to find most of the answers here starting on page 38

http://www.healthy.arkansas.gov/aboutADH/RulesRegs/OnsiteWastewaterSystems.pdf

I cut and pasted a section from the code below:



11.6.4. Tank proportions. The liquid depth of any tank compartment shall not be less than 36 inches and shall not exceed 72 inches. The minimum horizontal distance from the inlet to the outlet of any tank may not be less than 72 inches. Storage capacity is required above the liquid line to provide for that portion of scum that floats above the liquid in all septic tanks. On the average, 30% of the total scum will accumulate above the liquid line. In addition to the provision for scum storage, one inch shall be provided at the top of the tank to permit the free passage of gas back to the inlet and house vent pipe. For tanks having vertical sides, the distance between the inside top of the tank and the liquid level shall be 12.5% of the liquid capacity or 9 inches, whichever is greater. In horizontal, cylindrical tanks, this distance should be equal to 20% of the tank diameter.

Assuming the liquid level means the bottom of the 4" inlet, the distance from it to the ceiling on my tank is 7", so since 7" is less than 9", does that mean that this tank is made wrong ?

Arky
 

Smooky

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The liquid level should be at the same level as the bottom of the outlet not the inlet. The inlet will be 2-3 inches above the liquid level. Measure from the bottom of the outlet to the inside top of the tank to get the free board.
 

Arky217

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The liquid level should be at the same level as the bottom of the outlet not the inlet. The inlet will be 2-3 inches above the liquid level. Measure from the bottom of the outlet to the inside top of the tank to get the free board.

Ok, I'm starting to get the picture.

With the liquid level being at the bottom of the outlet hole, that makes the liquid level 39.5" from the floor of my tank.

Both of the tee's that came with the tank extend 18" from the bottom of the hole and 1.5" from the top of the hole.

So, that means the outlet tee will extend 18" or 46 % into the liquid and the inlet tee will extend 16.5" or 41 % into the liquid.

So, should I leave the outlet tee it's full length ? ( if so, it would extend into the liquid a little less than half way)

And should I cut some off of the inlet tee ? ( Let it extend into the liquid, say about 6" or so ? )

Thanks,
Arky
 

Smooky

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11.6.5. ……The inlet tee shall extend at least 6 inches below the liquid level in the tank and extend above the liquid level to a minimum of one inch from the top of the tank. In no case shall the inlet device be greater in length than the outlet device.

11.6.5.1. Outlet tees shall extend to a distance below the surface 35 to 45%of the liquid depth.

Arky… In NC we do tanks differently. We have a good on-site waste water program with much different rules for septic tanks. I do not agree with some Arkansas rules but you are in Arkansas so you have to do it according to their rules. …. The tees that came with the tank sound like they meet the Arkansas minimum standard or are at least very close, so I would leave them as they are now. No inspector is going to measure ,much less turn a tank down because the outlet tee is ¼ inch too long. Don’t worry about it. The inlet tee will need to extend at least 9 inches below the bottom of the inlet opening, so as long as you meet that rule you could cut a little off. I do not see a reason to do it but you could. The best thing to do would be to wait till after it is inspected.
 

hj

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qutoe; 1) Should the top of the inlet tee be open or closed and why ?

2) Should the top of the outlet tee be open or closed and why ?

3) How far down from the bottom of the inlet hole should the tee extend and why ?

4) How far down from the bottom of the outlet hole should the tee extend and why ?

WHY are you asking these questions? The inlet and outlet tees and drop pipes were installed BY the manufacturer, so why would you be doing anything to "adjust" them? LEAVE THEM ALONE!!!
 
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