A $10 check valve got stuck and the pump couldn’t pump the groundwater out so we got completely flooded.

You need to find the source of the mold: leaking water pipe/roof, ground water penetration, drain pipe leak, windows/siding aren't weather tight or flashed correctly and they let rain in, gutters and downspouts aren't working correctly, or tenants are screwing with you intentionally.

If they leak into the soil and groundwater the insurance will not cover the expensive cost to clean it up. surprisingly it's a fairly common issue with the number of aging tanks out there. 

Condensation isn't the issue, humidity is.Something is adding moisture- is it the foundation allowing in ground water?

Nine out of ten sump liners I've opened up were heavily "stained" in both Florida and Georgia from only "ground water". 

Hi,This is a more technical question, I have a house with brand new septic system installed, absolutely new drain field and we realised it already saturated in 3 months!! was expected to take around 15-20 years! I che...

You may actually have a ground water problem or water leakage issue (besides the refrig line). 

Is it showing up a few hours or a day after rain (ground water rising)?

We are doing a green concept that will use solar energy, geothermal HVAC, and ground water technology.

They make handy storm shelters, among other uses.Basements are holes in the ground, and therefore are susceptible to flooding from rainwater from above and groundwater from underneath.