Hi Everyone,

Has anybody had experienced water filling up on a n air vent on a slab, no basement or crawlspace SFR home? My tenant called me and reported that there was water present in the air vents located in the bathroom, kitchen and in one of the bedroom. If anyone has had this problem, I would appreciate your feedback. Any recommendations as to what to do and who to hire to find out the problem will be appreciated. Thanks in advance

What sort of air vent?  If you have a slab on grade house, there is not any reason for HVAC vents to be placed under the slab. Usually a furnace or A/C would be placed in the attic, and only plumbing would be placed underground.  Do you know where this goes or what it does? 

The SFR house was built on 1970's. The slab has both the air vents and the plumbing for the house. I guess it was the framework for that community at that time.

@Oliver Santiago

In slab, HVAC duct systems are fairly rare but they do exist. I have only had experience with one that filled with water over the last 40 or so years that I have been in the business. Unfortunately, the fix is not easy or cheap. Outside of the chance that someone filled the duct system, either intentionally or by mistake, with water, the only explanation is a high ground water table that has allowed the water to leak in. If it has done this once, it will continue to do it every time the ground becomes saturated. This being the case it means you now have a very real possibility of mold growth in the duct system.

The only real fix, that I know of, is to abandon the under slab duct system. The vents would need to be sealed with concrete to prevent water and mold infiltration into the house. A new HVAC duct system could possibly be installed overhead in the attic if the house allows that possibility. If not other alternative means would need to be considered.

Does it happen to all the vents? Does it get worse with humidity? Is it a coating of water or actually filling the vent?

This could also indicate a leaking water pipe under the slab. Have you been having high water usage?

@James Canoy it only happens to the vents on the kitchen, bathroom and one bedroom. All of which are in line with one another.  It only happened last couple of weeks.

@Mike McCarthy I have investigated and went to the property. I have hired a plumber and asked to investigate. So far he had seen a broken pipe from the washroom and that was fixed. and yet the next day water still came in on the three vents. So I asked the waterproofing expert and his professional opinion is there might be a crack on the slab that water seeps through, but honestly he doesn't know. Finally @Tom W. you are right. I asked my HVAC guy and he said he had encountered similar problems like the one I had. He said unfortunately we have to abandon the old vents and to re vent to the attic. He said once water comes thru these vents, once the ground becomes saturated, it will be filled with water and theres pretty much nothing you can do and with these kind of weather that were having I'm not catching a break. (12 inches of snow last Feb 9)

Thank you all for your input.