Why is there air in the plumbing sytem?

Answer 1

You may have a tiny leak in your system somewhere. Just enough so that when the system is on it sucks air in. Use the bleed valves to bleed air out when the heating is not running.

Water contains tiny bubbles of air and as it heats up, as in a heating system, a water heater, or just as it comes from an underground pipe and heats to the ambient temperature of your house, the air will be released from the water. In other words, the heating causes the air in the water to go beyond the saturation point, be released, and collect in the high points of the piping system. Vent valves or automatic air vents should've been included during installtion, but if not, it's a pretty simple job to do yourself. Just close the valve to the branch you want to work on, or close the valve that supplies the house if you have to. Then open the hot and cold faucets to depressurize the system. Locate the highest point in the system and install an saddle type air bleeder valve. The hardest part will be drilling the hole in the pipe, but most people can drill a hole. Once the hole is there bolt the valve on, close the faucets, and turn the water back on to the house. Now you can open the vent valves and bleed the air out periodcally. You'll know when it's time when you hear the pipes making that gurgling sound. You may have to install more than one bleeder valve if your system has more high points that will trap air. Just remember, once the air goes up and gets stuck in a high point it can't go back down. Any home improvement store will have the saddle valve, and if you don't know what you're looking for, ask them and they'll get it for you. There will be better installation instrustions on the package than I gave you. The pressure in the pipe is greater than the outside pressure so I don't see how it's possible for air to get sucked in. Good Luck! (You can do it!)