ECN Forum Forums Code Related Discussion NEC & other Code issues Raintight EMT Fittings

Check out the commentary to Section 225.22:

"Therefore, raceways should be installed to permit drainage through drainholes at appropriate locations."

This, to me, encourages the installer to drill drainholes at low points of the installation. By limiting the size to 1/8", most insects will be excluded.

I was wondering about drilling holes in Bell boxes as far as the UL listing goes. The side mounted brackets they provide with the box are really flimsy. I usually install a couple screws through the back with a washer and some caulking. I just call them plugged drain holes to meet code.(ha) I also found that water seeps in through the hubs, so I always caulk those too. The boxes are designed so that when you screw the hub seal in all the way it leaves a nice little cup for water to sit. I guess if they made them any better they would cost more than 3 bucks.

Regarding hubs leaking, that's not defective fabrication--it's how the threads are designed. U.S. NPT threads do NOT seal--they have a spiral leak at the tips of the threads. That's why plumbers have to use either pipe dope or teflon tape on their threads.

This goes back into the 1800's, when the pipe threads were standardized. They could have specified the threads so that they would acually seal, but they didn't. There exist other threads that do actually seal. (I believe the BPT threads will seal without a sealant.)

Solar Powered,
You bring up an excellent point about the threads on U.S. electrical equipment.
Most U.S. electrical equipment, hubs, connectors, EMT, rigid, IMT and conduit and fittings use what are called straight NPSM threads. These threads are known not to be reliably watertight at even slight positive pressure without the addition of thread sealant.
The NEC requires explosion proof equipment and conduits for classified locations such as, fuel pumps, to use tapered NPT threads like plumbers and gas pipe fitters use. NPT threads compress and lock together when tightened, so they are water and vapor tight and are also resistant to loosening from vibration.
Whenever I have to work with pipe, I always carry both types of dies in my threader kit, because once you get out of that classified location you can go back to using the factory NPSM threads that come on our rigid conduit.

As an example, this is why when you try to use a 3-foot long piece of 1/2 rigid pipe from the hardware store to make an extension pole for a ceiling fan, it does not thread properly into the fans hub. The fan hub in NPSM and the pipe is NPT.
Something that everyone has probably tried at one time or another in a pinch.