I just put new tires and tubes on my mountain bike last night. The tubes have been sitting in my closet for several years, never used. (I haven't ridden this bike in at least 4 years.)

When I got home from work tonight, I found the front tire had gone totally flat. I removed the tube, pumped it up, and immediately felt the air slowly leaking out of the valve. The tube itself has no holes.

Is it possible to have the valve stem replaced, or is the tube trash? It's a schrader.

I'm not even sure what brand it was...