Bubbling Air in pipes of boiler, need to remove air - how to

I Bought a condo two years ago, had some issues with leaking plumbing and water temp, so i called a plumber out who changed a valve and charged me $350 and spent 15 minutes on the job. Now i'd like to try and do some repairs myself. That being said heres my issue.

I have a space / water heater system. I believe there is a ton of air in my system. When the water heating system is on alone everything is fine, but once winter came and I turned on the space heating switch, I've been hearing all sorts of noise. I looked through all the baseboards heaters to see if there is an air pressure valve i could release the air from and was unlucky to find it anywhere.

Next i watched some videos on youtube on how to release the air pressure with hose and bucket. I've found some luck with this but one specific problem is that all videos show a step of shutting off the zone valve and shutting off the return.

I'm confused with the layout of my heating and plumbing system compared to the videos online. I have a small apartment 650sq ft and assume that its all one zone.

Basically every 5-10 minutes I hear a knocking and rush of water going through the pipes below the boiler. A forceful type of bubbling. Also, there are 3 pipes that go to a drain and sounds like water dripping through one os those pipes, a constant drip.

I've attached some images so you can get an idea of my setup if someone could walk me through what valves should be open and closed and how to drain the system of air, or what other problems i may have.

I will admit at first that I'm not a boiler guy, but can help in some situations until it gets outside my realm of comfort on advice. I'll let you know when that is. Hopefully one of our members who is more familiar will join in soon.
It's important to know if you had this happen last winter or if this is a new problem.
What you are describing seems to be an expansion issue in the pipes such as water being relieved and filling again to make up pressure.

This issue did not happen last winter.

I don't really know what that means to have an expansion issue, I'm just looking to resolve the noise and hopefully prevent any further issues.

I attempted to purge the system yesterday with the hose and bucket method. I closed the return handle (red handle - left side of photo). Attached the hose to the black spicket in the middle, the left one of the two. Opened the spicket and let it drain for about 30 mins, every 5-10 mins the rushing gurgling nose came and went, the hose would sputter out air so I feel like that was working. I closed it off once that noise stopped coming and opened the return valve again.

I thought that everything was great and done until late last night about 8 hours later, the noise started coming back in the same method, every 5-10 mins rushing gurgling noise.

I would be okay with that if it was in my basement but its pretty much in the center of my condo.

Any other advice would be greatly appreciated.

on the return pipe from system

run a hose to a drain, crack open the drain. open your make up water. with burner off, circulate system. for an hour

turn off drain, turn off pump. let system sit. for an hour. purge again. do that 3 or 4 times,

sometimes on a big system, i let it run all night.

best case scenero, is to bleed at the upper most point in system, if it was plumbed that way

your pump,


your problem is, I do not see an air separator or expansion tank on your piping.