Did a small job yesterday making a short run of outdoor conduit
watertight; homeowner gave me the connectors (elbows and compression
fittings) and had me replace the existing ones.

The compression connectors were labeled "concrete tight", and when I asked
him if that meant they were truly watertight, he said he was told they
were by someone where he bought them (which I think was a big orange
store).

So what's the recommended practice to make metal conduit watertight? Yes,
I know one can use plastic, but I'm interested in how to make the steel
stuff withstand weather.

I have seen wiring failures in outdoor conduit caused by the ingress of
water; in one case, a nick in a wire caused by pulling it caused corrosion
to the point that the wire actually broke in two.

(This installation is mostly under an eave, so watertightness isn't
super-critical, but keeping water out is a Good Thing.)



*Under the eave is considered a damp location, not a wet location. I don't
recall seeing watertight connectors for EMT. The compression connectors are
considered rain tight. Use conductors rated for wet locations and be
careful not to nick them and they should be fine. Use weatherproof boxes
with weatherproof covers.

When I did conduit jobs in concrete decks and such I always wrapped the
connectors with duct or gaffers tape. Even if they were considered concrete
tight, without the tape wrap some concrete juice would always seep in and
harden in the conduit.

PVC and liquid tight conduits are waterproof with proper fittings.