The sump pump gurgles only when the newly installed radon system is turned on. The sump pump has a sealed lid. The gurgling (bubbling) sound is definitely coming from the sump not the tubes extending from it. The pump does have a check valve. In normal operation it empties water from the sump well and shuts off with no problem. While idle (no water to remove) when we turn the radon system on you can distinctly hear the water in the bottom of the sump gurgling/bubbling. What is happening? How to fix? Is the check valve slightly leaking air back into the water in the pump well? Is there possible a hole in the pump well pan into the surrounding gravel which allows the radon fan to pull small bubbles through the pump well pan?