Have a Whisperflow pump, been trying to fix air problem for weeks. New o'ring. Basket water level drops 50% in 8 hours. I've cleaned and tried silicone grease, and teflon plumbers putty. After pump stops I can see a bubble about every 10 seconds go to the top of the lid. The pump primes in about 30 seconds, should I worry about it? Anything else to try? New lid?