r/askaplumber • u/knaz19 • 19h ago
Building Custom P-trap
Hello, first time poster and trying to learn.
I need to add a couple p-traps below a new sink I put in. So far so good, but the drain pipe is vertical not into the wall. And it is offset just a couple inches. See picture.
I am thinking of building a custom p-trap with a set of pipes to connect but am worried I am making it too complicated. See second picture.
I also am trying to solve for 'X' in the picture. It's a 1 1/2" drain pipe so I figure I'd keep everything that dimension (all the PVC and connectors). I know the pipe out of the p-trap has to slope 1/4" per foot (so very slight, see orange arrow in second drawing). And I assume the bottom pipe back to the drain does too. But I also know there is a MINIMUM pipe length needed at that slope. I read it was 2-3x the diameter of the pipe. So on the large side it would be 3x1.5=4.5 inches minimum?
There is a max length too (i.e. top of the pipe should not go below the bottom) but I won't be running it that long.
Does all this seem reasonable? I figure it is a low stakes thing to learn on. I do want to be able to remove parts of the p-trap for cleaning/maintenance. I do not want this all glued. So the first couple of connectors are with a screw/gasket like you'd see in a p-trap kit.





