Thanks for all your responses. I want to be sure that I understand correctly. When you say, "But it is probably soft enough that a small snake can push right thru" do you mean that a small snake would not be effective because the material would still be hanging around inside the pipe even after snaking with a small snake? The pipe is only 1.5" diameter so I dont know if that could take more than a 1/4" snake without damaging the pipe.
That is what I am saying.
That said, I had good luck with a
got a RIDGID PowerSpin Plus.
I powered it with a reversing drill. I expect the higher RPM of using the drill helped where hand rotation may not have.
I bought it for a lavatory drain, and it worked great for me. I actually went through the 1-1/4 trap, and before I knew it, it had played out about 12 ft of snake, and the blockage several feet below the santee had been cleared. I was prepared to enter at the trap adapter on the santee, but thought I would try the lazy stay-dry top entry. I know it has limitations.
I only snaked through the trap in case it worked. I was expecting to have to do more disassembly. It was really handy to be able to run water during the snaking.
I am not sure which horizontal you are talking about, but either way I suspect my PowerSpin Plus could make it. I am thinking the spinning probably helps. That said, I have only used it the one time so far.
I expect clearing a bathroom drain path to be easier than for a kitchen. I suggest looking in Yelp for a drain cleaning specialist near you. I would tend to avoid the franchises, but I expect that some franchisees could locally be good.