Q for the HVAC gurus - is the condensate drain supposed to have a weep hole?

One of our HVAC furnace/a/c units (we have two, one for each floor) decided that the mechanical room would look much better if it had a swimming pool in it. I eventually tracked down the majority of the leak to this weep hole on the condensate line connection:

There is also condensation dripping from the refrigerant line that's above the condensate drain, but a) that looks like it's been happening for a while and b) it's the odd drip, not the 3-5 gallons of water a day I caught coming from the weep hole.

After some percussive maintenance on the condensate drain line and ensuring that the downstream pipes from it where clear, it seems that the weeping has stopped for now. However I noticed that the other furnace does not have a weep hole in the condensate line, so I was wondering if there is supposed to be one. It kinda makes sense for me to have one so the furnace doesn't flood if the drain is blocked.

Anything else I can do, preferably work that doesn't involve taking parts of the furnace apart? I don't seem to be able to get hold of our normally reliable HVAC guy so I kinda need to DIY this for now until I can find someone else to check it over.

Also, am I correct to assume that the furnace assembly isn't supposed to leak air at every joint? Looks like the cold air is currently merrily blasting past all the aluminum tape in multiple locations, so I guess I get to fix that, too.

That hole is just the preference of the installer. Some guys like them to assure that there is no vacuum present in the drain line.

I'd remove the elbow and install a safety float switch in its place (Rectorseal SS1). That way if the drain ever stops up again it will shut the unit off before it floods. They are cheap. I know we pay about 15 bucks for them wholesale.

Here in Texas where I work we install most of our systems in attics so a flood situation gets real expensive real quick so we always have primary and secondary drains plumbed in with a safety switch. 

In reply to BoxheadTim :

Cousin Eddie is spot on with his advice on the drain and emergency switch.

On the leaking air, no that’s not supposed to happen and you’re losing air the should otherwise be cooling your house.  I’d recommend taking the covers off and gasketing it with adhesive foam tape.  The foil tape is OK for small air leaks but not so much on covers that get removed and reinstalled. 

Edited to add; while you’re in there vacuum or flush the drain pan clean with some water to make sure the crud that plugged the drain in the first place is all cleaned up. 

Our condensate line has T in it and it open at the top. I capped it because it was making a weird noise, but the other end of the pipe is open into the condensate pump anyway.

My in-law's AC system needs to have the condensate line cleared every few months. It grows weird stuff in it and I just stick the shop vac on it to clear it out. They live on the Georgia coast though, so the drain line is a slow drip pretty much all the time.

I have a pan float switch on our upstairs unit, cheap insurance. The unit in the basement has one too, but our dedicated dehumidifier keeps things pretty dry.

Thanks, that sounds like I've got to figure out if all the joints in the drain line are actually glued and if not, clean out the line. Plus potentially fit one of the recommended switches.

And I better figure out if the panel where I noticed the air leaks is one of the panels I can remove for maintenance or not. The air leak is at the joint between two components (the furnace itself and the box that contains the a/c coil).