Need Help on Plumbing a Sanitary Tee into a Septic Tank

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by DECJ, Mar 25, 2011.

  1. DECJ

    DECJ New Member

    Messages:
    21
    Location:
    La Sal, Utah
    After a lot of frustrating trouble-shooting, we finally discovered that we had a major toilet paper clog in the first chamber of our 1000 gallon concrete septic tank. We just had the tank pumped out this morning and after talking with the pump-out guy and then calling the septic tank manufacturer, they both recommended that I install a sanitary tee on the otherwise straight input pipe that enters our septic tank. And here is a pic of the current input line:

    decj_septic_tank.jpg

    I now have the 4" sanitary tee, but I have a question before I proceed. I know that I will be gluing on a straight extension pipe to the bottom port to extend down into the middle water layer in the tank, but what do I do with the unused upper port of the tee? Should I cap that off, or should I leave it open? Also, if I cap it off, does the fact that the end of the input line will now be below the surface of the tank contents cause any undue back pressure as sewage & waste water leaves our house and dumps into the tank (as compared to the straight pipe that is currently above the tank level now)?

    I would sure appreciate any help or advice on this.

    Thanks,
    Don
    Last edited by a moderator: Mar 26, 2011
  2. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,143
    Location:
    South*East
    Leave the top of the tee open, this will eliminate the problem of any back pressure.

    John
  3. DECJ

    DECJ New Member

    Messages:
    21
    Location:
    La Sal, Utah
    OK, thanks much John. Leaving the top port open also works best for my application, as the clearance between the top of the sanitary tee and the bottom of the inspection port lid (that is directly above it) is pretty limited and I would have had to get creative to shoehorn-in the fittings for a cap arrangement.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,835
    Location:
    Cave Creek, Arizona
    I cannot imagine HOW installing a tee on the line will prevent whatever happened. The water will rise in the "drop" pipe to the level in the tank, so any TP or other "light" material such as grease will float inside the pipe until there is enough pressure to "push" it below the water and into the tank's chamber. I have seen MANY clogs occur in the inlet tee, and the cure was to break up the clog with a board pushed down through the access opening.
  5. DECJ

    DECJ New Member

    Messages:
    21
    Location:
    La Sal, Utah
    I see what you're saying, but from what the pump-out guy told me, he said that 90+% of the clogs he encounters with concrete septic tanks, is right in the first section, where an open inlet pipe is close to first baffle wall partition, such that toilet paper essentially gets "thrown" into the wall and can start building up and backwards until the pipe itself is occluded and the back-up starts in earnest. (And I would post a photo of what we found in there, but it's pretty gross). He indicated that while he has encountered some clogs in a sanitary tee arrangement, he has seen far more from the straight inlet pipe set up I have. On the other hand, he indicated that he rarely sees the same issue with plastic septic tanks, as apparently, the baffle wall is a lot further into the tank than with concrete tanks.

    Anyway, with your input in mind, I am now wondering if I will be improving things or not with the addition of the sanitary tee. One thing for sure, we've already switched to single-ply Scott toilet paper and won't use anymore two-ply Northern after what we encountered.

    So instead of installing the sanitary tee, do you think I would be better served by simply cutting off a few inches from the 4" inlet pipe and calling that good?
    Last edited: Mar 26, 2011
  6. SacCity

    SacCity In the Trades

    Messages:
    189
    Location:
    Sacramento, CA
    I agree with putting the Tee on to direct the flow but why the drop pipe.
    Is not just having a Tee enough to redirect the flow.
  7. DECJ

    DECJ New Member

    Messages:
    21
    Location:
    La Sal, Utah
    It's my understanding that you want to be below the upper scum level and into the middle "water" level for new sewage from the house to enter the tank when you use a sanitary tee arrangement. Take a look at this typical diagram which shows the use of sanitary tees for both input and output lines:


    decj_septic_tank_cutaway.jpg

    With the way my existing straight pipe comes into the tank above the tank level, eliminating the down pipe would probably put the bottom output port of the sanitary tee directly into the upper scum layer, which is probably not a good idea. So it looks like I either need to have some length of down pipe if I use the sanitary tee, or else, I should just cut 3 or 4 inches off of my straight pipe and just forget the sanitary tee.
    Last edited by a moderator: Mar 26, 2011
  8. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
    679
    Location:
    Houston, Texas, United States
    Go with the drop pipe and San tee !
    Also go with a filter in the outlet tee these are required in some states but not Utah,
    they help keep semi solids from running into your drain-field prolonging the life of your drain-field
    Last edited: Mar 26, 2011
  9. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
    679
    Location:
    Houston, Texas, United States
    Plumbing santee into septic tank

    Go with the drop pipe and San tee !
    Also go with a filter in the outlet tee these are required in some states but not Utah,
    they help keep semi solids from running into your drain-field prolonging the life of your drain-field
  10. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
    679
    Location:
    Houston, Texas, United States
    A WORD ABOUT PUMPING SEPTIC TANKS

    Check both compartments yearly and pump before enough solids accumulate in first compartment to spill over into second compartment. Usually less than sixteen inches - consult manufacturer of your tank.
    Wrap a piece of white towel around the end of a long pole to check solids level in bottom of your septic tank. A healthy, properly sized septic tank might never need pumped, but not pumping when needed will result in grease and solids getting out to the leach field. Particulates, grease and solids create 'biomat' in the leach field percolation area, eventually causing it to fail and need replacement. Every three to five years is the normal cycle for pumping a septic tank (less often in warmer areas and/or lower usages). Should you live in an extremely cold climate, never have your tank pumped in the fall or winter - only pump in the spring. Septic tank water only avoids freezing through biological/bacterial activity (fecal matter decomposing).
    Refill your septic tank with water immediately after having it pumped !!!
    Without water on the inside, an empty septic tank is under extreme stress resisting the weight of backfill around it. This is especially true when soil is wet and when tanks are not properly bedded properly in plenty of gravel (selective, draining backfill). Stress is critical when sewage pumpers park too close to the tank, so always keep their truck at least 20 feet away. With enough stress, an empty concrete and fiberglass tank will crack, start leaking and eventually have to be replaced.
    Install an effluent septic filter and spray it off during yearly inspection of tank
    Sieve filters keep larger particles from getting out of the tank and compromising the leach field by clogging soil pores and causing failure (bio-mat). Septic filters are cheap insurance, installing easily in the second compartment of your septic tank.
  11. DECJ

    DECJ New Member

    Messages:
    21
    Location:
    La Sal, Utah
    So, have you seen any clogging issues with the use of a sanitary tee as hj has?

    I would love to do that, but I have no outlet tee, just a flush-to-the-wall outlet pipe. And as you can see from this straight-down pic, there is no room in the cast concrete output "chamber" to put in any kind of fitting, far less a filter unit:
    [​IMG]

    In fact, a straight piece of 4" pipe won't even go down that hole ... only a 3" pipe, and that's with no fittings coming off the 4" output pipe.
  12. DECJ

    DECJ New Member

    Messages:
    21
    Location:
    La Sal, Utah
    I have a 1000 gallon Dura-Crete tank that is made in Salt Lake City, and while it is a respected design around here, it really doesn't have discreet compartments, other than perhaps the small "well" that leads to the outlet pipe. There are two concrete baffle or partition walls that go full-width and hang down from the ceiling of the tank ... one right near the inlet line, and the other quite close to the outlet line area. They only hang down 22" off the ceiling, and with an internal tank depth of 57", that means that 35" from the floor of the tank to the bottom edge of the two baffle walls is essentially a common open area for the tank. There are a couple of very small weir type openings in each baffle wall up high in the center, but those only allow some exchange between the three "compartments" if the tank really goes into some sort of an overfilled mode.

    As it turns out, we get almost no sludge level with our tank. We first had it pumped out in 2008 after it had been in service for 9 years, and there was only ~6" of solids at the bottom. Now a little over 2 years later, there again was almost nothing in the bottom. Perhaps this is due to the fact that it is just my wife and I, we have no garbage disposal, and we typically don't put stuff in the tank that shouldn't be there (toilet paper notwithstanding).

    We are sensitive to the upper scum level and are aware of the downsides of getting any of this material into the leach field. In fact, we were worried that might have happened and maybe it was our leach field lines that had clogged up causing our back up (before we subsequently discovered the major toilet paper clogging disaster in the inlet line and first "chamber" of our tank).

    All good advice

    Again, as I indicated above, I would really like to have a filter or at least a sanitary tee on my tank output, but it's unfortunately impossible due to lack of adequate clearance as shown in my photo.
    Last edited: Mar 26, 2011
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