Better choice for a kitchen sink p-trap: ABS and cemented joints or polypropylene and slip joints?

Question

As I need to redo the p-trap system under my kitchen sink and I am all but an expert in plumbing matters, I would like to understand which one of the two alternative solutions shown below is the preferred one.

Solution 1 is proposed in this YouTube video and shown in the first picture.

Past the initial slip joints that connect to the tailpieces of the dual sink, only ABS pipes and ABS fittings cemented together are used, resulting in a fixed, highly leakage-resistant assembly.

Solution 2 is proposed in this other YouTube video and shown in the second picture.

Despite the plumber in the video keeps very confusingly calling it an ABS p-trap, this system has no ABS in it but it is fully made of polypropylene (PP) parts assembled together by slip joints.

This is my non-expert assessment of pros and cons of the two solutions.

Solution 1 has two advantages: a lower probability of leakage thanks to the cemented joints and a lower probability of blockage due to the larger inner diameter of the 1.5" ABS pipes compared to that of the 1.5" PP tubular.

Solution 2 has two advantages as well: an easier installation thanks to the larger number of degrees of freedom and a much easier maintenance, with many options to take it apart without damaging it.

On the other hand, maintenance of solution 1 is not that painful as it can be taken apart without damage as well, albeit less conveniently, by unscrewing the two slip joints up at the tailpieces and the nut at the tail end of the p-trap. In the worst case, if needed, just one cut at the pipe before the p-trap allows disassembling and the use of a slip joint or a shielded coupling when putting it back together makes it more maintenance friendly. However that nut at the end of the p-trap that makes solution 1 easier to maintain makes it also more prone to leakage as that screwed joint is always under water by design.

At the end, is it basically a wash and just matter of personal preference or is there a cogent reason that makes one solution definitely the superior choice?

Answer 1

The polypropylene trap fittings (white, or black) are mechanically joined not glued.

So you're conflating two entirely different systems. Even the sizes of the pipe are different between trap fittings and drain pipe.

Polypro trap fittings of either color join to PVC or ABS via a trap adapter mechanical joint. The PVC or ABS after that mechanical joint between the two types is glued. Since there are no polypropylene fittings suitable to connect all the way to the sewer, there will be a change to a suitable drain pipe at some point, typically where the trap enters the wall, and all the inside the wall and under the floor plumbing will be PVC or ABS (or cast iron if you like self-abuse or want a really quiet flush and are willing to abuse yourself for it.)

Your second picture appears to show a galvanized iron drain pipe at the trap adapter, which probably joins to cast iron plumbing, and no PVC or ABS at all. The brass nut is a clue. Likely that is an older house from when galvanized and cast iron were the standard drain pipe materials.

The only place I will use a glued trap is a 2" minimum diameter under a concrete floor. Anywhere else, a glued trap is stupid, since you have to take a saw to it and throw it away, rather than disassembling it, for any maintenance or changes to the sink. Under a concrete floor, you try to avoid ever needing maintenance, and when you do, you're chiseling up the floor anyway.

Plumbers may love the first version, as it ensures additional fees later on. Nobody else does. If somebody's diamond ring ends up in the trap, you have to disconnect that glued mass from both sinks to make any use of the union on the trap, and awkwardly try to remove it to access the trap dangling off the bottom of it. With slip joint trap fittings, you undo two nuts and pull just the trap bend off - 12 times easier. Good luck getting the first version back together, too.