This is the exhaust vent from a gas fired heating system.
That drip, right at the joint, started a year ago. I'm assuming it's from condensation, and would otherwise drain back into the heater, except for a bad glue joint. What's the best/easiest way to address this? I'm thinking to just turn the heat off the next few warm days, and layer on some glue at the joint.
Is it glued at the moment? If not, your plan is fine. Turn of the heater, disconnect, glue, reconnect, turn heater back on.
Ideally, though, the pipe would be angled slightly downward towards the outside to prevent the condensation from backing out to the appliance in the first place.
You'll probably have to cut the elbow out, and replace it. The elbow should be glued, so removing it without damaging it or the pipe will be nearly impossible.
You'll either have to replumb the line from this point on, or use couplings and nipples to make up the pipe you have to cut out.
If the joint is leaking condensation, it's also leaking combustion byproducts. This should be fixed as soon as possible.
The line should slope; as it does, back towards the furnace. There should be a condensate drain near the furnace, to handle any moisture that drains back. Draining towards the outside, can cause problems with ice.
