Hi. Welcome to Just Answer.
The condensate drain line is to drain off any excess condensate that is generated by the unit. Excessive condensate can be produced by the environment in the home, or by a low refrigerant condition. As the units were just topped off I would presume that there is higher humidity in the one air conditioners area that it handles. It may be a kitchen or an area that has moisture being generated (spa, pool, sauna, etc.), as opposed to the other units that handle bedrooms, or family rooms, that dont generate much moisture at all.
If it is just a drip I wouldnt be concerned. If it gets to be a dribble have the AC man come back out. He may have left a valve partially open and the unit has a low refrigerant level.
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Thank you for replying. It is drips, however some times it drips faster than the other times and some times no drips at all.
There is (1) 6" open pipe closer to the unit under the roof line outside and (2) similar pipes on the other side again under the roof line. I also see (2) open end pipes coming out of the wall close to the ground right under the (2) that are up high under the roof line.To clean the drain line, where do I need to put the shop vac hose please?
Good day, Heidi.
The drains for the AC units should be directly over a window. That way the condensate drips on the window and alerts you to a potential problem.
As long as the units are draining the lines do not have to be cleaned out. I personally have never seen one that is plugged unless a human has done something to cause it.
The reason it drips only at certain times is the AC units "cycle". In other words they are not always on and cooling. When they receive a request for cooling from the homes thermostat, and start to cool, that is when moisture from the home begins to condense on the evaporator coils. The evaporator coils are what the systems fan blows the homes air over to cool it. Once the home has cooled to the selected temperature the units shut off and that is when the accumulated condensate begins to melt off of the evaporator coils. It then drains into the drain tube and out of the building.
The tubes close to the ground go to the hot water heater high pressure relief valve (TPV) drains. If water is comning out of them it means that the hot water pressure relief valve is either doing its job, and venting excessive pressure, or they are old and have started to leak. In either case a call to a licensed plumnber is warranted.
NOTE: The hot water pressure relief valve is a safety item and should never be ignored or bypassed. It can cause a very big explosion if the hot water heater builds up enough pressure.
Here is a demonstration video of one exploding.
Thank you for your reply. I am still not quiet understanding that dripping is good or is a sign of potential problem.
I don't have any drips from the pipes closer the ground. There is only drip on one of the three pipes located on the roofline. There are several videos on line shows how to clean drain line and they use Dry-Wet shop vac and recommend to do it every 6 months. I would like to know which one of these pipes needs to be cleaned every 6 months.
The once every 6 months is a sales gimmik. It is intended to say "Hey look here! Arn't we doing a lot for the small fee of just $69.99* we charge to service your HVAC unit twice a year? (*freon, travel time over 1.3 miles, servicemans lunch break fee, and other parts not included) ;-)Granted you should service your heating system ibefore winter and your AC before summer every year. That is where they get the every 6 months from.
Heidi, there is no reason to clean the drain lines unless something is clogging them and the condensate overfills the catch pan under the AC units. There are safety switches and alarms (not on all models) that keep the trays from over filling. You will know well ahead of time if the tubes are plugged.
As for where the water is coming from; Refrigeration units cool things by removing moisture from the air. Hence the name air "conditioner". This is true with refrigerators, freezers, air conditioners, and large commercial plants. The only difference is the air that they do this to. A refrigerator or freezer only conditions the air inside of it. A home air conditioner conditions the air inside your home. A commercial plant conditions the whole warehouse.
To remove the moisture in your home the AC fan takes the air inside your home from the return air duct (this is where you install the air filter at) and blows it over the evaporator coils inside the AC unit. As the air passes over the coils the moisture in the air condenses onto the coils. It is just like a kitchen window in the winter when a lot of holiday cooking is going on. It collects moisture because it is colder than the air in th ekitchen. The warm moisture laden air releases the moisture as it cools against the cold window and you get condensation.
The water you see dripping from the pipe is the condensation that is from the moisture that the unit is removing from the home. It is perfectly normal to have a little bit of water come from the AC unit. The "normal" amount should not be more than dripping. If at any time it becomes a steady dribble the unit should be looked at.
Here is a video I made to illustrate the difference.
Please click here to see the video.