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Problem: Water or moisture buildup in my pressure switch tube on my 80% furnace.

Problem: I own several rental properties. I am having a problem with moisture buildup in my pressure tubes on my 80% furnaces. The tubes stop up with water and the furnaces shut down.

Answer: FYI, regarding moisture buildup in pressure tubes, I simply moved the pressure switch above where the tube connects to the inducer and the moisture problem went away (on both Goodman & Rheem furnaces). Below we have a real good Youtube video which shows how to troubleshoot pressure switch problems. This Youtube video was made by grayfurnaceman. Thanks grayfurnaceman! We sell many different types of pressure switches on the following page: Please click here to see the pressure switches we sell.  If you have any other questions please email us at: or comment below. We would love to help you out and have your business!

16 thoughts on “Problem: Water or moisture buildup in my pressure switch tube on my 80% furnace.

  1. My pressure switch was high enough, but the location of the tube was below the drain. Must have been installed this way. I moved the tube to a higher elevation and it is impossible for the water to enter the rubber tubing now. It works- fantastic. It works great.

    1. Fantastic! Glad to hear you fixed the problem and you let others know how you fixed it! Awesome! Thanks so much for sharing this. Hope your post will help others. God bless you! Steve

  2. I have a problem with water in black drain hose on my goodman furnace its so bad I have to drain it twice a day l can usually get around 20ounces of water at a time can youhelp

    1. Hi Nick! I do not know if you have a worn out leaking drain hose that is causing the water or if your furnace is not tilted properly and not allowing the water to drain correctly. If it is a worn out drain hose that is leaking, then this hose will need to be replaced with a new hose. If you would like for me to look up parts then please send me your furnace’s model number and I will try to get you a part number for the hose. It would be best to email me at our email address so I can give you a parts list. I hope you have a nice day! Steve

  3. My little helper decided to pull the hoses off my pressure switch while i was removing my inducer motor. Now im not sure which hose goes where. Is the “-” hose go to the blower and the “+” hose go to combustion chamber? Please help its freezing in my house.

    1. I am sorry, but I do not know for sure. I would think that the minus would go to the combustion chamber because the draft inducer is supposed to be pulling negative air from the combustion chamber and out to the vent. I am sorry that I do not know for sure on the answer to your question. It should not hurt to do some trail and error and see what works. Steve

  4. Is a pressure switch supposed to hold moisture? Mine has/had a lot of water in it and it’s mounted much lower (floor plate) than the one shown in the video. At this point I can’t get the furnace to come on at all.Thoughts?

    1. No sir, a pressure switch should not hold moisture inside of it. This can ruin the pressure switch over time and possibly cause your furnace to not work. If water is building up inside your pressure switch I would recommend disconnecting the pressure switch tube from the pressure switch so it does not get damaged and use a wet vac to make sure the drain on your condensing furnace is not stopped up. The pressure switch is made to sense negative air pressure not air and water. I hope you can get your problem solved. I hope you have a blessed day. Steve

  5. I had a issue with water in the tube was freezing at the point where the hose attaches to the black plastic drain pan directly under the burners. I don’t know why it gets that cold in there. Seems air is drafting back down the exhaust tube from outside freezing the water in the drain pan when the furnace is not running. I’m not sure how to fix this yet. When i removed the pan to see what was going on inside, i found ice and water at the ends of what i think is the heat exchange tubes. ( 12 or so tube outlets with a strip of metal inside each of them). The drain its self was not clogged, nor was there any water in the pan its self, just some accumulation of ice and water in the pipes where the strips of metal were. The pressure sensors are above where the pressure tube attaches to the pan so the water did not actually freeze in the rubber tube but it froze inside the plastic outlet on the pan. In the past month i had to fix the issue with the furnace not starting by removing the rubber tube from the sensor and blowing in it to clear obstruction. I thought this was debris and the pan needed cleaning. This is how i found out about the ice. i was expecting to find bugs and other stuff in there, to my surprise its ice. At least now i know that i can jam a rod in the hole to clear the ice. I do not know if this is normal to have this much freezing happening inside the furnace. Very surprising.

    1. Hi Chad! Thanks for posting this problem. This is why condensing furnaces can not be installed in unconditioned spaces. I am guessing that your furnace is located in an area where it is pretty cold. I would suggest trying to reposition the furnace so that the water drains out the front into the condensate drain line. The furnace might just need to be tilted a little bit like a 1/4″ to get it to drain properly. If the furnace is level or tilting back the water will stay in the secondary heat exchanger and can freeze up. You might need to open a register near your furnace to keep the temperature above 32 degrees. Sorry that I do not have a definite solution to the problem. Hope you can find an easy fix. Steve

  6. I don’t know if this will help. I had the same problem with water in my pressure switch tube. The problem was a clogged drain from the inducer. It had lots of bugs and gunk. Hope this helps

    1. Hi Eric! Thank you so much for taking your time to post this valuable information. Yes, a dirty draft inducer clogged with bugs and gunk can cause water to going into pressure switches. Thanks!

  7. I had the same problem, the reason was due to a tear in the diaphragm in the pressure switch which I found by taking it apart. This hole allowed flu gas to continue to pass through leaving moisture behind.

    1. Thank you so much for offering this information about a torn pressure switch diaphragm that caused moisture build up! If anyone needs a pressure switch we sell lots of pressure switches on the following page: Please send your furnace model number and I will try to find out which pressure switch your furnace uses. Thanks! Steve

    2. This was not helpfull at all evryone knows how to test pressure switches and 90 % of them on the market today are adjustable with a #1 square bit, my question was recuring moisture in the vaccuum hose ty

      1. Sorry that I do not know the answer to your question. I tried to answer the question in our post. I hope you can find the answer soon and let me and others know. Thanks! Steve

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