Ok, so we broke down and called a plumber: vent stack had a major block and when that didn't stop the gurgling in our toilet, plumber installed secondary vent under bathroom sink. The gurgling stopped when water is running and we thought issue was resolved. Tonight however, I ran water to do dishes and when I let it out, gurgling. Two of the three times I refilled the sink it made the toilet gurgle when I let water out. What in the heck is the problem now?? Drainline is clean, vent is clean, septic line is clean and tank isn't full. I'm beyond frustrated at this point.

  • Are you sure the vent stack is still clear? You said you the gurgling stopped, now it's back. Maybe whatever clogged it before clogged it again.
    – Johnny
    Commented Nov 6, 2015 at 22:48
  • 1
    I note in your original post that the problems stopped for about 1 month after having the septic tank pumped. If you have 2000 gallon septic tank with two people using about 100 gallons per day, it should take about 20 days before the septic tank is refilled after pumping. Can you provide more details about the septic system? How old is it? Have you ever inspected the drain field? Was the inlet baffle plugged with soap when you had it pumped?
    – user39367
    Commented Nov 7, 2015 at 0:56
  • The stack is still clear; when the septic was full it backed up into it. This is the fourth time it's left and come back since August. We were told by the septic company that we had a couple of years before the tank needed pumped again. I do not know the age of the system or the status of the drain field, but we have no soft spots or dampness in the back of the house where it sits
    – user45197
    Commented Nov 7, 2015 at 11:06
  • Ok, so the gurgling is only happening when the washer spins or the dish water drains. Showering, flushing, and sinks running don't cause issues. We are also having issue finding where the vent stack actually connects to the plumbing under the house, so we are wondering if it could just be a ventilation issue, since the 2nd smaller vent seemed to help
    – user45197
    Commented Nov 8, 2015 at 18:33

1 Answer 1


Based upon your description and comments, I am going to guess that the trouble lies with your septic system not draining (or barely draining).

If you are new to septic systems, there is a lot of useful information online about the theory of operation and the different models commonly in use.

Regarding the "pump the tank again in 2 years" advice, that is boilerplate advice from a septic pumping company and it says nothing about the condition of your system, other than the tech servicing it thought it was working. With a properly functioning conventional system and 2 people living in a 3-4 bedroom home, provided no one flushes a garbage disposal or anything nasty down the drain, the pumping interval can often be extended to 5 years.

On the other hand, if your drain field is mostly plugged then you will begin having trouble about 1 month after it is pumped, since that is roughly the time it takes for the empty tank to fill. A failed drain field will not necessarily cause water to pond near the surface. For example, one such failure occurs when more than just clear effluent leaves the tank into the drain field. After awhile, that condition looks like this:

enter image description here

If the drain field pipes look like this then there will not be visible wetness and the sewage is going to go the only other place it can --back into the house.

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