I have a large fish tank in my house, and would like to run a 1\4" reverse osmosis/deionization (RO/DI) top off water tube through an exterior wall into my house so that I can have the top off tank outside.

Can I drill a hole through the wall, caulk in a 3\4" PVC pipe, run my tube and then fill the gap left in the PVC with fireproof putty? I'm in Los Angeles where the weather is niceish, and the tube will be from a covered patio where it would be protected from elements.

Is there a better way to get an electrical cable out (for the pump) and 1\4" tubing back in (for the water) through my exterior wall?

1 Answer 1


I don't claim to know California building code. That said:

I don't think the building code cares what you do with your aquarium piping, so long as it doesn't connect to your residential plumbing. Do what you want with that top-off tube.

As for electrical, if you want to run wire then it's a bigger deal and there are lots of rules you'll need to follow. Too many to list here.

Essentially, you'll be looking to install an outdoor outlet that you can plug your pump into (If you try to permanent wire it, then even more rules will apply).

  • The power is controlled & switched by a controller that's inside with the aquarium. I was thinking of essentially putting an extension cord through the opening. Bad idea?
    – anon
    Commented Jun 11, 2015 at 15:18
  • 1
    @MatthewRuno, This article uses the National Electric Code (NEC) to address your very question. Specifically, "flexible cords must not be: (1) Used as substitutes for the fixed wiring of a structure. (2) Run through holes in walls, structural ceilings, suspended or dropped ceilings, or floors. Your best bet is to get an exterior receptacle installed, complete with weatherproof "in-use" cover.
    – mjohns
    Commented Jun 12, 2015 at 11:57

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