My house has a natural gas boiler that provides 3-zone heat (via baseboards) and domestic hot water (via a 4th zone connected to an indirect fired water heater).
Had to replace the 75gal tank for hot water in the spring, due to it leaking, and the manufacturer warrantied the tank - 12 years old - at 100%.
Did the swap myself.
Thought I did an OK job, but now that heating season is upon us, I'm not so sure. I must have introduced some air into the system, resulting in gurgling baseboards. I've popped the end caps off a couple segments of baseboard, but cannot find any sort of bleeder valve, like the cast iron baseboards in the old house had.
So the question. How do I get the air out of there?

I’ll let the master Steve Lav show you how it’s done: https://www.youtube.com/watch?v=Yi6WYbBRiGc

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Originally posted by PowerSurge:
I’ll let the master Steve Lav show you how it’s done: https://www.youtube.com/watch?v=Yi6WYbBRiGc

I wouldn't count on his being installed correctly (for ease of service) like the one in the video.

OP, every boiler system is different, depending directly on the installer.
Most baseboards have a manual air vent on the outlet side.

An overall photo of the system would be of great help.

At the end of each loop you probably see a hose bib (boiler drain) followed by a valve to isolate the return. You connect a hose to the boiler drain, stick the other end into a big bucket of water, close the isolating valve, open the drain, and allow the auto-fill (or engage the manual water fill valve) to push water through the zone.

You'll have water flowing from the isolated zone into the bucket for while but at some point you'll get bubbles, possibly explosively - i.e. lots of air. Then when the air calms down you know you have the air out of that zone and you move on to another zone. After closing the fill valve, closing that boiler drain valve, and opening the zone isolating valve. [I guess it does not hurt to leave that zone closed while working on the others.]

You'll want a big bucket. A floor drain close by is good as well. It'll make a mess. You can always put the bucket into a laundry tub.

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Originally posted by PowerSurge:
I’ll let the master Steve Lav show you how it’s done: https://www.youtube.com/watch?v=Yi6WYbBRiGc

Boy, he does mumble, and apparently talking into the mic is optional. but I get the gist - thanks.

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Originally posted by motor59:

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Originally posted by Excam_Man:
An overall photo of the system would be of great help.

Similar, but slightly different than the video... only one circulator pump and its on the other side of the expansion tank.

But that does raise another thought. Above the expansion tank is a chunk of cast iron - I believe its called an air scoop? atop it is a little silver cylinder with a valve cover cap. According to the orange apron-ed guru at the big box hardware store, that's a bleed valve and the cap should be on loosely to vent air. He says that it if its leaking water, the bleed valve has failed and needs replacing.

Well, mine was tight. I cracked it and got a hiss of air for a moment, then a trickle of hot water. So that's suspect now. Or is it? I never know if I should believe the orange apron guys, although this one was my age and had the appearance of a second career type.

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Originally posted by Woodman:
At the end of each loop you probably see a hose bib (boiler drain) followed by a valve to isolate the return. You connect a hose to the boiler drain, stick the other end into a big bucket of water, close the isolating valve, open the drain, and allow the auto-fill (or engage the manual water fill valve) to push water through the zone.

You'll have water flowing from the isolated zone into the bucket for while but at some point you'll get bubbles, possibly explosively - i.e. lots of air. Then when the air calms down you know you have the air out of that zone and you move on to another zone. After closing the fill valve, closing that boiler drain valve, and opening the zone isolating valve. [I guess it does not hurt to leave that zone closed while working on the others.]

You'll want a big bucket. A floor drain close by is good as well. It'll make a mess. You can always put the bucket into a laundry tub.

I've got a sump hole about 6' from the boiler, so that should be easy to do. I'll just pick a day when the temp is above freezing.

Just need to suss out a way to override the electric zone vales one at a time to flush the zones.

You may be able to turn all of the zones on then shut the main power to the boiler / zone valve relay. Or possibly manually open the zone valves; some of them have a manual bypass lever. You'll figure it out.

Your setup is clean and typical. The zone return isolation valves are all lined up with the drain valves above them.

The end of the hose has to be submerged in water for you to know air is coming out.

My buddy and I purged a hot water loop on a 12 story building once ... the bucket was near exploding when the air finally made it to us. Very dramatic. For you it will be a 30psi experience, probably. Worse that can happen is you'll over-pressurize the boiler, at which time the relief valve will blow.

Over-pressurize the boiler?

Would that be from my manual water fill overwhelming the drain line?

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atop it is a little silver cylinder with a valve cover cap

Our system has a couple of pill bottle-sized brass cans with a bleeder valve on top. When I hear air in the system I loosen the caps and let the trapped air out of them. It may take several repetitions (especially after refilling the system) but that always works for ours.

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Would that be from my manual water fill overwhelming the drain line?

Doubt it. You'll likely turn the fill on part way, anyway. If you have an autofill, it will be a metered addition of water, not pell-mell inundation, and is probably set at 12psi.

Boiler relief valve is factory set to blow at 30 p.s.i. whereas your home pressure may be 40-70. So if you inadvertently shut off the purge line while the fill is still on it might pop the blowoff valve. No big deal. That's actually the way I fill my boiler.

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Originally posted by motor59:

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Originally posted by PowerSurge:
I’ll let the master Steve Lav show you how it’s done: https://www.youtube.com/watch?v=Yi6WYbBRiGc

Boy, he does mumble, and apparently talking into the mic is optional. but I get the gist - thanks.

Well excuse me for trying to help you. I won’t make that mistake again. You go and try to have yourself a nice day.

PowerSurge- Sorry that my observation on Steve Lav's diction and on-air style rankled you. It was just that - an observation - and not directed at you. As a matter of fact, my original reply did thank you for reminding me that YouTube should be my first source for how-to suggestions beyond car stuff. Somehow that didn't make it into my post... one of the reasons I don't like posting from my phone. Maybe I should have inserted a wink emoticon to reinforce the spirit of the comment.

Well, I'll be damned... your system does have all the nice options for service!
Whoever did the install is no spring chicken when it comes to boilers. Backflow preventer, low water cutoff, ball valves for everything - including hose bibs, relief/backflow piping, etc...

Turn off the gas valve, close all 4 loop valves, turn up all your thermostats, hook up hose to one loop and purge air from system. System will automatically refill to set pressure.

To answer your question about the air vent on the air scoop above the expansion tank, if its leaking water - it is bad.

Notes, the valve (nice for service) on the expansion tank is a code violation.
Looks to be corrosion on the pressure relief, so it should be changed.

And stainless B-Vent smoke pipe? Sexy!

As Excam stated, "hook up hose to one loop and purge air from system" does suggest you can skip the bucket. Running water through a loop for 3-5 minutes should purge air from that loop. You'll hear a difference in the sound of flow as it comes through the pipe and hose.

An air hammer is even worse. A column of trapped air slamming back and forth within a large-diameter gravity HW header converted to forced water (circulator) makes for a serious pipe-shaking racket.

Relief valve - yes, weeping at the outlet. You typically have to drain the system to replace it. I cannot tell if your supply zone lines also have valves on them (it looks like there is a check or balancing valve visible on one branch). Check operation yearly, regardless. Never ever cap or plug a relief valve [KA-BOOM].

Expansion tank - If someone shut the valve above your expansion tank, your relief valve would discharge every time the boiler water expanded (unless cushioned by a volume of trapped air). Same if a pre-charged expansion tank developed a defect in the diaphragm or bladder (or an old-style expansion tank became waterlogged).

Thanks guys for the replies. I'll remove the handle from the expansion tank valve, to minimize the code issue somewhat. And we'll look at replacing that relief valve in the spring, when there isn't snow on the ground...

Air vent replacement and zone purges will be this weekend. Will let you know what happens.

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Originally posted by motor59:
PowerSurge- Sorry that my observation on Steve Lav's diction and on-air style rankled you. It was just that - an observation - and not directed at you. As a matter of fact, my original reply did thank you for reminding me that YouTube should be my first source for how-to suggestions beyond car stuff. Somehow that didn't make it into my post... one of the reasons I don't like posting from my phone. Maybe I should have inserted a wink emoticon to reinforce the spirit of the comment.

Just tell him you own a Toyota and all will be good

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Air vent replacement

Might want to hold off on that until the boiler is drained.

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Originally posted by HRK:

Just tell him you own a Toyota and all will be good

Matter of fact, I own 2 of them - an 03 Camry with 300K+ miles, and a 17 RAV4.

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Originally posted by Woodman:

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Air vent replacement

Might want to hold off on that until the boiler is drained.

Well, as Excam_Man noted, I have a metric sh!t-ton of ball valves on this furnace - I think I can isolate that portion of the piping enough to drain just a bit of water from the boiler itself, and swap the Hy-Vent® out. If it overflows, well, I still have a 1x3 furring strip cofferdam caulked to the floor around the entire boiler/water heater area, and it bisects the sump hole, so there's only one place for water to go. I'll swap this prior to the purge operation, in case I introduce more air into the loop during the process.

I have other issues with this furnace that I'd like to run past you guys, but let me resolve this first.