I've been trying to find an answer to this question for days but I still have uncertainty.

I'm doing a DIY project just for fun that involves passing two tubes and an electrical cord through a 1.5" thick wall of an Omaha Steak polystyrene cooler (styrofoam) that will be filled with ice water.

The tubes will be flexible vinyl or PVC (although that can change if needed).

One tube is 1/2" ID and is attached to a small submersible aquarium pump inside the cooler and will be attached to a 1/4" ID tube on the outside. This isn't for an aquarium and I don't have plumbing or aquarium-building experience. I'm guessing I need to use a bulkhead fitting with appropriately sized barbs or push-locks on each side, preferable with an L-shape (elbow) but that's not strictly required. However, will that work with polystyrene which is prone to compression? Is there a better, more reliable method? Will uniseals work any better with impressionable styrofoam?

The electrical cord powers the submersible pump, has a typical width found in lamp cords, and also needs to pass through the cooler wall but it doesn't have a circular profile so I don't know what I could use to pass that through the cooler without worrying about leakage. I'll cut and re-attach the cord so I don't have to worry about passing the larger connector end through.

Lastly, the third tube is 1/4" ID and contains the return-water. That can pass through the cooler above water level but I'd still like to avoid leakage when the water shifts within the cooler.

I plan to line the internal bottom and sides of the cooler with non-aerosol Flex Seal for added precautions. I could also use that around the fixings, assuming it would be helpful.

I've attached my plans in case it's helpful.

I'm a frequent contributor in another forum on data analytics and fully appreciate any time spent giving me advice. If this question is not relevant for this forum and you know of another forum that is more appropriate, I'd also appreciate that feedback.


Red sections show 3 areas in question

 

Why are you passing your tubing and power cord through the foam below the waterline? Why not just run them out the top or above the waterline?

 

Thanks for the response and good question.
I'd like to be able to keep the tightly-fit lid on the cooler. I thought about passing the tubes through the lid but that makes it more difficult to remove the lid when needed. It may be the best solution to figure out a way to pass the two tubes and wire through the top without making it difficult to remove the lid but I haven't figured out how to achieve that.

My initial plan to pass the one tube through the bottom end of the wall was motivated by:

1) Even if all holes are above the waterline, I still want to ensure they are leakproof when the internal water shifts around, although underwater passage will have to withstand water pressure where above-water passage will not.

2) With all holes at the top, the structure may become weaker. It's not meant to be portable but it may get a jolt or shift now and then. If there are no ideas to make this work as shown in my diagram using bulkhead fittings or something similar, would those ideas work if the holes were along the wall above the waterline where there may be an occasional splash?

If passing it through the top is best, perhaps I could cut out a few inches to allow all 3 items to pass through the lid-edge but I would need to figure out a way to keep the tubes and wire in place within the cooler so the lid isn't lifted.

 

The only product I would trust for your application is marine grade caulk, or, pure silicone that is submersible (like aquarium sealant). Any of the expanding glues or foams do not hold up well under water; once they leak it's over.

 

Thanks for the tips, @jrsick. I'll look into that.

 

So your contraption does not have a lot of water so no pressure. Really all you need is a flexible sealant/adhesive.

PL Polyurethane construction adhesive will bond to all the materials, form a water tight joint and be a bit flexible!

 

Thanks, @Marq1. I'll look into this as well.