I can't seem to keep the drip rate on my MRC CR2 calcium reactor constant. I set the drip rate, come back several hours later or overnight only to find that the drip stopped and the water level in the first chamber has dropped. I then have to open the needle valve on the second chamber, purge out the air, and set the drip rate again. This can't be good. I'm feeding the reactor with a small line tapped off of a Reeflo Marlin pump. Any idea why this is happening?