well, if you leave it go the air won't build up that fast, will it? You should be able to let it alone until the morning, then suck out the air through the airline tube, check on it again at the end of the day, until you get your next pump, right? Also, there was another person on here who had a similar thing happened and he found that he could go with the gravity effect of a one-way valve on the end of the airline tube, feeding into the sump. the gravity pulled water and air out and kept the U clear. No need for a pump anymore.