Septic Tank Tee's

[Arky217]

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

[flyingvan]

I'm not familiar with the tanks with no baffle so answer #4 won't make sense.

1) Open.  You want the sewage to inject into the effluent freely without any suction forming.  When the effluent gets up to its level you don't want things backing up the pipe.   You also don't want wet saturated soil sucking back into the tank when you get it pumped.  Also when someone flushes a tampon (my GOSH those things swell up huge) that's where they'll get stuck so it gives you a way to get it out.      Don't ask why I know this, and don't ask who the REPEAT offending visitor was.

2) Open so the outflow equals the inflow---with it closed you'll create a siphon like a toilet and it could surge.

3) Maybe 10" down.  The sanitary tee top to bottom keeps the surface sludge from plugging things up.

4) Usually goes down to the level of the pass through hole in the baffle, which you don't have.  I'd just have it somewhere near the middle.  As to the why---

   Things you flush will float or sink.  They get into your tank and go up or down.  There's bacteria that feasts on sinkers and bacteria that feasts on floaters.  A sludge slowly accumulates top and bottom too.  As stuff is digested it reaches a neutral buoyancy and goes to the middle----this is when it's ready to drift out to  your field.  You flush something, it injects into the effluent, then displaces some of the middle water up the outflow tube into the leach field.  If the bottom is too high or too low it'll be in the sludge layer.

  --Pump your tank every few years.   There is stuff that won't degrade--onion skins, synthetic fibers, hair.
  --DO NOT flush antibiotics, harsh chemicals, and especially engine oil.
  --If you're leaving for awhile dump your box of baking soda from the fridge in the toilet and flush it.  The spike in pH is like a party environment for your microbes.
   --DO NOT waste money on septic treatment microbes.  You provide all the necessary microbes every morning.

And now for info you DIDN'T ask for.  If it's in the budget always get a concrete tank.  Infiltrators are supposed to be far superior to perforated pipe and rock (plus you don't have to buy the rock). 

[JRR]

If I ever install (another) septic system, I intend to include a effluent screen filter.  Protects the drain field of whatever design and acts as an indicator of tank conditions.
.
http://water.epa.gov/scitech/wastetech/upload/2005_07_28_mtb_effluentscreens.pdf

[John Raabe]

Good information. I saved that link.