HVAC Unit Leaking Water - Common Causes

Here's a few common causes we've found over the years.  

• Roof Top Mounted Equipment (Aka Packaged Unit or RTU).  Its important to note that most RTUs are mounted on a 'curb' which is simply a very large hole in your roof.  If something goes awry within the RTU, water could easily find its way into your space below.  
• Drain Line. The Drain Line removes condensation water from the unit and disposes of it in a proper location (usually piped to a plumbing drain).  If and when the drain line becomes damaged or clogged.  It will leak water.
  • Recommendations: 
    • Have the drain line inspected, quarterly
    • Blow out the drain line with compressed air or nitrogen, quarterly
    • Treat the drain pain for algae by adding pan treatment chlorine tablets, quarterly   
    • These recommendations are traditionally performed during a routine preventative maintenance visit
• Drain Pan.  The Drain Pan catches all the water created by the process of condensing cold air and provides a 'catch basin' for all condensation to flow into the aforementioned drain line. Should Drain Pans crack, rust, warp, be installed unlevel and/or become defective in anyway, they will leak water. 
  • Recommendations: 
    • Standing water in a drain pan is a bad sign of something not draining properly.
    • Have the drain pan inspected quarterly
    • Remove algae from drain pans and treat regularly with chlorine tablets, quarterly 
    • Ensure drain pans are 'arranged to drain' properly with angle adjusted for flow to the output hub
    • Replace any damaged drain pans immediately. 
• Equipment Panels.  The removable equipment panels and rubber gaskets on your HVAC equipment can deteriorate with time.  Screw holes become worn from years of removal and maintenance and in general, like an old car, they can leak when infiltrated with driving rain water.  
  • Recommendations: 
    • Check panels for good form fitting tightness quarterly 
    • Upgrade to larger screws when smaller screws experience wear and tear
    • Consider quick temporary fixes until the unit can be replaced, such as: taping of the seams with uv rated tape to temporarily keep water away 
• Unit Levelness.  Make sure the packaged unit is installed 'level' or plumb as per manufacturer's requirements.  The internal drain process is engineered with all the just right angles and degrees needed to remove water effectively from the unit.  
  • Recommendation: 
    • Put a Level on the unit and make sure it's nice and plumb!
• Filter Restrictions.  Dirty filters can affect air flow and increase condensation build up and even ice formation.  
  • Recommendation: 
    • Remove and replace filters on a quarterly basis at minimum.  
    • These recommendations are traditionally performed during a routine preventative maintenance visit
• Duct Work.  Damaged or collapsed duct work can cause air flow issues that lead to condensation creation.  
  • Recommendation: 
    • Inspect duct work for holes, damages, restrictions. 
    • Inspect vent louvers to make sure they're adjusted and 'open' properly for original design intent. 

This article has been shared by Direct Service, Construction and Design to specifically accommodate our intended clientele.  The intent of sharing this information is to better inform the public of these general topics, expand knowledge and safety for all and provide crucial information in regard to their MEP and building systems and/or assets. It is NOT our recommendation that any article recommendations or how-to scenarios be attempted by anyone other than a qualified or competent person.