Don't use bleach on a clogged line. It won't clear it and will just cause corrosion on what ever metal it come in contact with and can also accelerate corrosion of the coil in some cases. You really need to get a hvac company out to check the drains and clear the lines. Rust in the auxillary pan means this has happened perhaps a few times before. A properly install main drain will have a tee in it before (capped) and after a trap (capped or uncapped) where you can see if and where the drain may be clogged and perhaps use air pressure to see if that will push the obstruction thru. Other causes could be a system that is icing up, a cracked drain connection, a rusted pan and some systems (carrier) have a metal drip catch on the horizonal units to guide the condensate to the main pan that when dirty runs the water over the coil into the duct. It's probably just a clogged drain, but as you can see there may be more to it that may need attention. *I've had to replace many an indoor coil because it rusted out prematurely due to chlorox used the wrong way.

No, it is not a single handle. I thought at first it was residual from the 5 ft hose from the shower system that converts to hand held. After its use, I turn the valve in the actual shower so it will drain from the actual fixture, then after a minute or two, I will turn the converter at the top of the shower where the system is hooked up, to the right, and drain what is left in the hose from the hand held portion. 95% of the time all of the residual water will drain. I don't understand where it is coming from but it will happen 8-12 hours after the shower had been used. Why all of a sudden is beyond me, but it will diminish after about 20 minutes, so it has to be coming from somewhere, as there is no leak that I am aware of and no water is in use when this happens. The water heater is on the other side of the shower wall. I don't believe there is any connection between the two?

I think my vent is 4", I have a Bryant Plus-80 furnace, and I just replaced my hw heater, (I'm in BC Canada so YMMV) - the flue hat for the hw heater is sized for the vent that's there, I hadn't thought of that aspect - if I replace my furnace with a HE one - since I just shelled out on the new hw I wouldn't want to change it just yet (but I guess I would run the plumbing for a he hw heater when I do the furnace- Both furnace and hw heater Y into a single vent of course, if it was hw only, would there be a reducer that runs off the flue hat? I could certainly see a difference if it was only one appliance using the vent, but I've never seen any condensation coming back down....I wonder if OP's issue might also be some negative pressure....which could be dangerous. jmnoelle13, can you try a test for us? Get a stubby candle like a tealight, and place it right next to the flue hat on top of your hw heater, when the heater's at work, and see if the flame of the candle is drawn towards the flue hat? If it is, all is well in terms of airflow, if not, your system or parts of the ventilation system in your house is drawing combustion products back down the vent, which is very dangerous. Your new furnace should have two side vents, one for exhaust, one for combustion air. You probably didn't have direct combustion air feed before, so you should be better off in that regard. As for reducing the vent size, can you drop a sleeve down inside the vent from above?

It's where the condensation comes out from your central A/C unit. This is perfectly normal and is supposed to happen...actually it has to happen because your A/C removes the humidity from your home so the air feels much cooler.