Hi,
There may be a number of reasons why there is air in your water lines. If you have had some plumbing work done on your home recently, the plumber may have turned off your water and drained the lines so that he could do his work. When the water is turned back on there is air in the lines. Usually the plumber will open a couple of faucets in the house and run the water until the air is illuminated from the lines. If you are continuing to have air in your lines you should have a professional plumber out to your home to evaluate the situation.
Thank you
Angelo Mike Counsil Plumbing
1915 O'Toole Way San Jose, Ca. 95131
408-512-1805 snipped-for-privacy@mcplumbing.com