A snake can punch through a soft clog, yielding temporary results, but not clear the problem. A powered snake, run back and forth through the clog along with plenty of water to flush the debris downstream, is frequently needed.

JM$.02W

Most drain cleaners can run a camera down the line after they clear the clog. That will give you answers.

Yeah a clogged vent can do that. Air has to get in for the water to flow right, so if it’s blocked the drains back up even after you snake them. With only two people it’s probably not volume, more likely roots or a low spot in the line holding gunk. Camera inspection is usually the next step so you can actually see what’s going on.

Do you flush "flushable" bum wipes? If you are using them and flushing them, start putting them in the trash instead. I had constant problems in a rental house. I eventually figured out the "flushable" diaper wipes were part of the problem. The other part, I guesses, was a tree root in the pipe, that the wipes got stuck on, but that was too far into my yard. That house had very old clay pipes. Any leakage was minor enough if it did anything, it made my garden flourish. Although, maybe there was no root in the pipe. Who knows? Certainly, the problem went away when I started putting the wipes in the trash.

When a backup keeps returning after snaking, snaking is treating the symptom — a camera inspection is what finds the cause. Recurring backups almost always point to something structural: a belly (sag) in the line where waste collects, root intrusion, a partially collapsed section, or grease narrowing the pipe. The camera shows exactly where and what it is, so the fix is one targeted repair instead of another round of snaking.

One thing to rule out while you're at it: repeated backups can force water out through joints or cracks into the surrounding soil or under a slab, and that hidden moisture causes its own damage. In our work at ProLine Leak Fix Pros, we often pair a camera inspection with acoustic and thermal imaging so the homeowner sees both the blockage point and whether water is escaping — fixing the backup without checking for a hidden leak can leave half the problem behind.

With it coming back two days after a 70 foot snake, the vent is unlikely to be the cause. A blocked vent gives you slow drains and gurgling, not a full backup that keeps returning. That pattern usually means something physical in the main line: roots, a belly holding waste, or a collapsed section the snake just punched through. If more than one fixture backs up at the lowest drain in the house, that points to the main line, and a camera run is the way to see exactly what the snake is hitting.

Had this happen to me in a home I owned. A few things contributed the issue.

1. The house had not been occupied for a year so the pipes sat dry for that length of time.
2. When I moved in the toilets got switched from 3 gallon flush toilets to 1.5 gallon flush toilets and the pitch of the soil pipe in the basement which worked great for 3 gallons of water did not work great for 1.5 gallons of water.
3. The current absorbent toilet paper was a constant issue. Switching to Scott's toilet paper rated for septic systems eliminated the issue. Good luck and have the pipes scoped.