I've replaced the valve plate and the seals in the pump. I've deflated the bladder, weighted it down in the bottom of the pool and slowly  inflated it. NO air bubbles! Hose was under water too! It leaks. I've plugged the hose and it takes three days to get noticeably soft. But when hooked to the pump, it gets soft overnight. I'm at wit's end! matress is eight years old and has been moved once. Is there a pump that automatically maintains pressure by adding air when it senses a drop in pressure? I e-mailed Comfortaire and they said a slow leak won't make bubbles when the mattress is held underwater. I never saw an air leak that didn't make bubbles and I've been checking tires for slow leaks that way for sixty years!

My old Select Comfort had a pump that would maintain pressure.....until if failed.  It's now in the trash as I write this.