After having septic system pumped out several months ago, why does laundry room floor drain still back up? Drain has been snaked 3 times and it works for 1-2 weeks just fine, then back ups start all over again. We have even cleared the outside vents.

Since I just had this happen, I'm going to suggest that you have the pipe leading to the septic tank inspected. Just snaking out the drain may not be enough to remove a clog at the baffle. My pipe was dislocated by just about an inch by a landscaping truck running over it, and that was enough to let clogs happen right there at the baffle, too far for do-it-yourself snaking to help. I used Roto Rooter. It wasn't cheap to have them clear the pipe, but they figured out immediately where the dislocation was so I could get it fixed without digging up the whole system.

I might just have a solution for you but first I need a little more information. Dose the floor drain only back up when the washer discharges or will it back up when other fixtures drain? Back to you, Tom

Thanks so much for the responses. Very frustrating situation. Two weeks ago the drain backed up while using the showers and washer. Today it was only the washer.

I am going to assume you have lived in this house for some time and this is a new issue, right? I think schoolmarm is on the right track. I do a bit of septic work because of my current location. The pipe to the tank can break or dislocate, sometimes apparently on its own. The pipe from the tank to the field tiles can do the same a great plumber can diagnois this by sound when he rods. An average plumber with a SeeSnake camera rodder can also find the issue. Tree roots, dirt and bgravel can quickly close off a dislocated or broken pipe. BTW what diameter snake was used? The pipe going outside is likely a 4" cast or PVC, any idea which you have?

I Think schoolmatms situation is not a common complaint. It isn't every day you have a big truck or a backhoe running over your septic tank or drainfield. A simple check will resolve this issue. To check to see if you have a blockage inside or outside your house simply locate and open the outside cleanout and cycle the washer. If it backs up out of the cleanout then you have a septic problem. If it backs up out of the floor drain then the problem's inside the house. We have to know this before we can go much farther. Please get back to us with this information.
Now, if the septic system checks out and you've had the inside lines snaked out perhaps a Flood-Guard.(see image) is the answer. Check them out at
PlumbingSupply.com - Flood Guards For Floor Drains - check valves to prevent flooding.
Good luck. Tom

Tom I certainly understand your thinking but schoolmarm was talking about a landscaping truck running over the pipe between the home and the tank, not the field or pipe from tank to field. In any case I have seen several old clay tiles lines crush over 30-40 years. Apparently for no reason. The OP says the drain was snaked but that does not tell us much about the entire line to the tank and if the tank is over filled because the pipe to the field is clogged. Your test will help her isolate the issue and then we can really help and be specific.

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schoolmarm was talking about a landscaping truck running over the pipe between the home and the tank,

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And so was I, Generally speaking. Bob, And how common is that? Do you get lots of calls involving trucks in the OP's back yard? I think a better solution is what I've laid out. First check the septic system at the cleanout and we can go from 5there. Good luck, Tom

The truck scenario actually happened to me but I do agree it is not common. However, where I am most of our tanks are connected to the home and the field by clay tiles, no longer used because they do crumble and fail after 40 years. When we dig them up we never reinstall clay and go to PVC ASTM D3034 SDR 35. My post #7 does conclude that your test is the best next step.

Sorry if I confused the issue. Ballengerb1, thanks for clarifying. You did get my point. Around here, it's not unusual for heavy equipment (these are farms) to run over and break an underground septic pipe between the house and the tank. It's far less likely that the leach field or laterals will be involved because they're far deeper underground.

My point was that just snaking the drain might not reach the clog if it's near the baffle on the septic. Since the tank was just pumped, it seems unlikely that the problem is in the field and very likely that it's between the house and the tank. I was suggesting that further investigation might turn up something similar to my dislocated pipe. My situation has the water flowing smoothly for three weeks at a pop, then suddenly backing up because of the "lip" created by the dislocation.

Living on the Gulf Coast and in a urban area we don't get too many heavy trucks and tractors running around in our back yards so I'll defer to your experience. Good luck, Tom

Thanks for more responses. The outside pipe is PVC, but not sure of diameter. The snake was a 3/8 electric auger and also used a manual sewer tape. We also do not have an outside cleanout. Come to think of it, we started having the problem 2 months after the big Virginia earthquake. Had septic pumped in Oct. after the first back up, because it had been years since the last cleaning. So it just may be a dislocated or cracked pipe to tank.

Pump out and cleaning a setic tank are the same thing. I'd consider having a plumber with a SeeSnake take look for cracks and/or roots, rare with PVC but not impossible. Ridgid Seesnake 100' microREEL L100 & microEXPLORER system 40798 - Ohio Power Tool