Hi, I'm trying to figure out how to proceed with a project and hope I can get some feedback. I'm a DIY who learns mostly by reading forums, so I'm not an experienced plumber, though I have replaced supply and drain lines before.
Here's my long story: I've got a small cottage (800 sq ft) in a rural area that has been added to throughout years and years of updates, and I don't believe it's all up to code. All the plumbing is in a very tight crawlspace under the house. A few years ago, right before I bought the place, the township put in a sewer system. I was told by the previous owner that everything was hooked up to that system and I no longer had to pump out the septic tank. So I hadn't been.
Recently, my bathroom sink and shower drains began draining slowly. I decided to put a snake down there through a cleanout valve outside the house, and after progressing for a bit, it promptly got stuck. To the point (again, long story) where it would not come out for anything, even attaching a winch to the snake's line (the cable eventually snapped multiple times through multiple attempts). While trying to figure out what to do about getting the cable out, I did some investigation and realized some odd things. It appears that my cottage has two waste systems. The bathroom sink, shower, and laundry lines all tied together in a 1.5" line, went outside and into the ground, and (my guess is) into the old septic tank. The toilet and kitchen sink tied together in a 4" line, and after a bit of redirection, tie into the township's sewer cistern in the back yard.
The good news, I think, is I can leave the snake cable in the old pipe, and make new connections into the sewer cistern also. My options are to tap into it by digging and extending the 1.5" line that goes out into the yard, then connecting it to the 4" line that goes to the sewer cistern, or connecting the 1.5" line to the 4" line under the crawlspace.
Here are some of my concerns:
1) Neither the shower nor the laundry line have p-traps, and none of those 3 fixtures are connected to any vent (possibly why it was draining slow in the first place?). If I just run that combined line and connect it to the cistern out back, I will need to provide venting for them, right? Otherwise the gases will just run right out of the cistern and into the drains, and they'll continue to drain slowly? I don't think I have room to vent each one. Where they all connect and come out of the house before going down to the ground, I wouldn't be able to just put a tee there instead of an elbow, with a stack outside the house, would I? I've read about AAVs. Would I be able to install three of those, one at each fixture, instead? I understand the code varies on those.
2) When I followed the 4" drain, it goes downhill from the toilet, past the kitchen sink, and then down into the ground. It appears that somewhere near where it turns and goes into the ground, there must be a connection for a vent that comes out of the house. Is that proper venting? Isn't the vent stack supposed to be uphill from the fixtures, not below them? So if I connected the three additional fixtures (bathroom sink, shower, laundry), and they're uphill from that vent also, that wouldn't work, would it?
Sorry this is so long. I realize that the system could probably use an entire rehaul, but it's a cottage bought extremely cheaply a number of years ago that I'd rather not put much money into. Any feedback or observations would be appreciated.