Is adding an extra 90 sweep to my P-trap going to cause drainage issues?

Adding that extra 90-degree sweep effectively turns this into a running trap, which is going to be a massive headache down the line. Most codes actually forbid having that much horizontal travel or extra bends before the trap weir becuase it kills the momentum of the water and leads to constant clogs. If you glue that ABS togather now, you're basially locking in a drainage nightmare that you'll eventually have to saw off anyway.

The biggest mistake here is using glue-up fittings for a sink drain. You really want to be using slip-joint tubular piping under a sink. It’s not just about ease of installation; it’s about maintenace. When that drain inevitably gets backed up with grease or hair, you want to be able to unscrew the nuts by hand and pull the whole assembly apart without reaching for a hacksaw. Fixed glue-ups under a kitchen sink are almost always a recipe for future frustration.

Your best move is to cut that ABS back toward the wall and glue on a single **trap adapter**. This gives you a threaded end where you can slide in a standard 1-1/2 inch poly P-trap kit. Those kits are designed to swivel 360 degrees. Between the swivel of the trap and the ability to slide the tailpiece up and down, you can usally hit almost any angle coming out of the wall without needing extra elbows or sweeps. Don't worry about the vertical gap being a few inches. Just get a flanged tailpiece extension to bridge the distance from the sink basket to the trap inlet. It’ll drain way better than that roller coaster setup. Gravity is your friend here, but those extra bends are just friction points where gunk is going to collect. Once you switch to a swivel trap, that weird angle from the stub out becomes a non-issue because you can just pivot the trap to meet it.

So the swivel on those plastic kits can handle the wierd angle from the wall too? My setup is similar where the wall pipe points slightly to the left. I always figured the glue was safer beacuse it's permanent, but I guess that's exactly the problem if it ever clogs. Quick question though—if I switch to those slip joints, do I need to use that white plumbers tape on the threads? Or do the little plastic washers do all the work? I’m terrified of a slow drip ruining the bottom of my cabinet while I’m not looking.

Avoid tape on those slip joint threads. The seal comes from the compression of the poly or rubber washer, not the threads themselves. Adding tape can actually get in the way of a proper seat and cause more leaks than it solves. Just hand-tighten it and maybe give it a tiny snug with some channel locks if you relly have to. One thing to watch out for: make sure the beveled (pointed) end of that washer is facing into the joint. I've seen guys put them in backwards and then wonder why the cabinet floor is soaked ten minutes later. Get that orientation right and it’ll be bone dry.

Just make sure when you're sliding that tailpiece into the trap, you don't bottom it out. If it sits too low in the trap weir, it'll choke the flow and drain like molasses even without a clog. I usally mark it with a sharpie so I know I've got a couple inches of clearance.

Also, if you're using a metal tailpiece, grab the beveled rubber washers instead of the hard plastic ones. They seal way better on the metal and don't slide around as much while you're trying to get the nut threaded.

One thing people overlook when switching to the slip-joint kits is the 'LA Pattern' trap. It uses a ground joint union instead of just a washer on the trap curve. If you're worried about leaks but want the swivel, that's the way to go.

Just keep an eye on your trap arm pitch once you get it all lined up. You want about a 1/4" drop per foot toward the wall. If that extra sweep you were planning made the arm slope the wrong way, you'd end up with a permanent puddle in the pipe, wich is where the real stink comes from.