Need Ideas/Help on water intrusion with foundation.

[Jeff Beer]

Hey everyone,

To get to the point: I have an old house in PA, and groundwater is continually intruding/pooling in my in-slab/sub-slab HVAC air intake vents (floor returns). Yes, this is a thing, as the house is from 1940s. To note, this is a ranch style house that sits on a foundation, no basement. The lot/land is flat and level. 

From my consultations with a contractor and a foundation/leak detection company: I pretty much am told of these options as a resolution: 
Exterior French Drain, Interior French Drain, or both. 

This has been a nightmare, hoping the community could share some experience, wisdom, ideas, etc. I'm at the point of just selling off the property as-is, but ideally want to avoid that scenario. 

I guess my asks to the community is: 
1) Are there any other solutions beyond the ex/interior french drains? Interior French Drain will be very problematic as the property is occupied. As well, the cost will not justify keeping the house?
2) Have you had similar issues?

I'll gladly edit the post as more pertinent details reveal itself, and my apologies in advance if my thoughts are a bit sporadic.. again, I'm at wits end here.  Your help means more than you realize. 

[Scott Chilton]

It sounds like classic slab-on-grade water issues, especially on a flat lot. Floor returns act like magnets for groundwater, so the problem isn’t surprising.

Your main solutions are exterior or interior French drains, or both. Exterior drains are usually the least disruptive and prevent water from ever reaching the slab. Interior drains work but are messy, expensive, and tough with an occupied home.

Before committing to major work, you could also try improving grading around the house, directing downspouts away from the foundation, or sealing minor cracks in the slab. These steps often reduce water intrusion without the cost and disruption of full interior drainage.

Start by tackling the source of the water first. If issues persist, then weigh the cost of interior drains versus selling as-is. Addressing the water before it enters the slab usually saves money and headaches in the long run.