So I have an outdoor water fountain and there are two cables that go from inside the water fountain through a 1" PVC pipe to a dry junction box outside. The cables are for a submersible DC pump for the water fountain and for lighting.

Inside the dry junction box is an AC/DC adaptor for the pump and a high voltage to low voltage AC transformer for the lights, both of which shouldn't get wet. Unfortunately the junction box is below the water level of the fountain, so any leak in the pipe will be problematic.

I did a test run with one cable and a conical shaped rubber stopper which I drilled a hole in to run the single cable. I also applied some silicone to the outside of the stopped and the hole running through it. I used one stopper on each end of the pipe (so inside the fountain submerged and also in the junction box). This worked fine.

However, trying to use the same solution with two cables didn't work well at all. The rubber stubbed didn't really "close" or compress around the two cables well. Especially since they are slightly different shapes and sizes. One is round and the other is flat.

So can anyone suggest a good, reliable solution, that would be semi-permanent? That is my other concern: I want something 100% reliable but I don't want a 100% permanent solution. I could just fill the whole pipe with a waterproof epoxy, if I wanted to take things to an extreme, but I'm worried about some future where I might need to do some repairs and maintenance and I might need to remove or replace the cables.

I thought about using just silicone, but I'm not sure it would resist the water pressure - remember that the pipe is below the water level of the fountain, so there would be a significant amount of downward force on whatever sealing method I use. That's why I liked the conical rubber stoppers. The downward force just just wedges the stopper further into the pipe and increases the strength of the seal.

Are there, perhaps, rubber stoppers that would work with two different-sized cables?

I also thought about some kind of putty. Would plumber's putty do the trick? Or is there another kind of putty that would be better suited?

I also thought about something like a sprayable waterproof rubber or something? For example, I have used sprayable plasti-dip before and that dries like into a custom rubber coating. Is there perhaps a similar product that would spray out a little thicker and with more volume, almost like an expanding rubber foam, that would then dry into basically a custom, "perfect-fit" rubber stopper that I could later remove or cut through without much difficulty?

Or perhaps you have some other idea that is even better?

2 Answers 2


fit a tee to the pipe so that each cable can be separately sealed,

Ideally use the parts designed to do this job, conduit and waterproof cable glands, not "pipe" and "stoppers"

fitting a downward facing tee part way along the conduit will prevent any drips that get through the seal from reaching the electrical box.

  • That's a brilliantly simple solution and I feel dumb for not thinking of it, but I'm not 100% sure a T can fit where the tube is. Still, you're amazing and I'm going to check if that will work.
    – Daniel
    Nov 30, 2018 at 22:50

Even rigid pipe is considered a wet location when outside or underground. You are allowed to drill holes in boxes / conduit bodies up to 1/4" to allow for drainage. NEC 314.15 an open T would not be legal. I have used silicone to seal conduit that runs up a conveyor almost 100' at a 45 degree angle to prevent condensation from entering the controll cabinet. Then outside I drilled a weep hole in the conduit body no more water entering the cabinet. As a normal procedure in non hazardous locations I routinely drill a hole in the bottom of NEMA 3R enclosures outside to prevent water accumulation.

  • So do you have a suggestion on how to deal the pipe?
    – Daniel
    Nov 30, 2018 at 23:21
  • Silicone is a great tool here work a little around the wires and make a plug it won't need to be very thick if you need to pull it out its not that hard without doing any dammage. A simple hole in the bottom of the box will allow any moisture to drain as allowed in NEC 314.15 . 1/4". note 1/4" is the max size but it doesent say you can only have 1.
    – Ed Beal
    Nov 30, 2018 at 23:24

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