Question for a plumber on a forced hot water system

[Water Treater]

I would not reverse direction of water flow. Best to solve the root cause of the problem, which sounds like it's AIR IN THE PIPES.
The smallest amount of trapped air can (and will!) block water flow and explain the hot/cold water symptoms you describe.
If you bleed all the air from the system and you can still hear air (you should NEVER be able to hear water flowing), you're still introducing air into the system. Check suction side of pump to see if you're s#^&#^&#^&#^&#^&g in air. The air is being introduced somewhere, maybe when boiler (heater) shuts off and water begins to cool in the pipes. When you heat water and then allow it to cool, negative pressure (a vacuum) develops which will suck in air if plumbing connections are not tight.

[Steve K]

Thanks for all of your replies.

The entire system is only two years old. I am positive that I have a forced hot water system. I live in a condo with no attic.

Last night I drained the boiler and pipes. I attached a hose to the output pipe and I was able to get some air out of the pipes. When the heat came on this morning, I was not able to hear the water rushing through them. I will keep monitoring it for the next few days and let you know.

Thanks again,
Steve