Hot water heating system air scoops, air separators & air scoop questions & answerss:

FAQs about what a bulk air eliminator or "air scoop"does, where they belong, how they work to prevent noise and loss of heat in hydronic heating systems.

This article series answers most questions about central hot water heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects.

Air Scoops, Air Separators, Air Purger FAQs

These questions and answers about air scoops, separators or air eliminators on hot water heating systems were posted originally at AIR SCOOPS SEPARATORS PURGERS - be sure to review that article.

Illustration: G-F Air Cut air scoop or air separator on an older gas fired boiler provided by reader Matt.

That small 1/4" pipe plug atop the air separator is a tapping that can be used to install an air eliminator or float vent on many heating systems.

[Click to enlarge any image]

 

On 2019-11-17 by (mod) - trouble fixing an air-bound gas fired boiler heating system

You're on track, Brian but here are a couple of suggestions:

1. that tapping on top of your air scoop is the place where you can install an automatic air bleeder - probably that'd help you out

2. trying to purge air when the system is COLD will not work and in fact can make matters worse since when you open air vents high on the system piping you may let air in rather than out.

The system needs to be hot - at full operating temperature when opening radiator vents or baseboard vents.

Which is why you take care to not get shot with hot water when operating those controls.

Conversely, to install an automatic float valve or float vent at the air scoop tapping, you need to work when the system is COLD

And as there's probably no shutoff to isolate that air scoop, you either need to know how to work on the system live with water squirting all over the place or you need to get a trained service tech to help you out.

At AIR ELIMINATOR / FLOAT VENT REPLACEMENT https://inspectapedia.com/heat/Air-Eliminator-Replacement.php

you can see an example of that procedure where I replaced a leaky clogged air eliminator (float vent) on a heating convector. I let the system cool so as not to get burned and I had to be prepared for the water spray - the alternative is a lot more work to drain down the system and then re-fill it.

On 2019-11-17 by Brian - G-F AIR CUT air scoop

I'VE tried purging the air from all bleeders on base boards, nothing but water comes out,

I've connected hoses to boiler drain , closed isolation valves to zone lines and tried purging with auto fill water supply, normal and back flush.

I've tried isolating the boiler- draining water from zones at return line into a bucket ,and using a transfer pump from bucket back to

Zone line to purge the air, in the affected zone

Finaly replaced the circulator pump with new 3 speed ! Not the problem ,

Then I connected a garden hose (after letting boiler cool off all day ) to try and get more pressure to move air block NOTHING HAS WORKED.

The highest point for air to trap (Single story home-boiler in closet outside) is this air scoop ,with no bleeder just a plug.

I will put a TACO auto bleeder in if I can take this plug out without screwing something up.,

So with boiler shut down ( cooled to atmospheric temperature ) can I then turn on circulator pump and crack this plug until water comes out , or will it let preload pressure out of my expansion tank ?

Worried since the tank doesn't have a valve to recharge air pressure.

I'm sorry for rambling on, just going crazy with what should be a simple PURGE. THANKS IN ADVANCE.

On 2019-11-17 by (mod) -

Brian:

I cannot find the "GF AIROUT scoop" to see its product details. Please attach a photo using the add image button.

One of the good places but not the only place for an air vent is atop the air scoop - that's why there's usually a tapping that permits adding a vent there if one was not already installed.

Watch out: I do not recommend loosening a plug to try to manually release air at the air scoop, as you're likely to get scalded with hot nasty heating water.

On 2019-11-17 y Brian

My GF AIROUT Scoop doesn't have an auto bleeder installed on top !
It just has a plug where the bleeder should be ,If I cool the system down
Then turn on the circulator, can I then crack this plug to bleed out the air ?

It has a bladder expansion tank mounted below the air scoop that has no Schrader valve .
So not having a Schematic of how the scoop works, I don't want to open this plug and screw things up
With the expansion tank ,Thanks for any advice.

On 2019-07-22 by (mod) - best practice, the circulator pump is on the return side of the boiler

Andreas

Normally and as is best practice, the circulator pump is on the return side of the boiler

and the air scoop is above the boiler on the outlet side. That avoids the problem that you were discussing

On 2019-03-12 by Andreas

I understand that I want an airscoop before the pump (point of lowest pressure) yet a British lad on YouTube said you want to put the airscoop behind the pump cause otherwise the pump will be sucking air in? So how far from the pump should I go back?

On 2018-06-09 by (mod) - Air Scoop Size should match heating pipe size

Anon,

Thank you for the interesting question about whether or not an air scoop size needs to be matched to the line size on which it is installed.

According to the Taco air scoop and air Eliminator installation manual that you can find link to in this article, each air scoop size is designed for the line size to which it is intended to be attached.

That's another way of saying the air scoop size should match the line. That's because air scoops and eliminators are designed for a specific water velocity and volume through the device.

So for best results match the air scoop size to the line size of your heating system.

See details in this TACO AIR SEPARATOR INSTALLATION GUIDE / MANUAL [PDF]

On 2018-06-09 by Anonymous

Can I use 1 and a quarter-inch diameter air scoop when the old cracked one was a 1 in. would it make a difference to just neck down the bigger scoop to the 1in coper pipe

Can I use. 1and a quarter air scoop when the old cracked one was a 1 in

On 2018-01-27 by (mod) - air scoop needs to be at a local high point over the boiler.

The air scoop needs to be at a local high point over the boiler. There are recommended distances and locations that depend on the model and type of air separater "air scoop" that you have installed.

See the examples and installation sketches in this Taco Air Separator installation guide

https://inspectapedia.com/heat/Taco-Air-Separator-Installation-Manual.pdf

On 2018-01-27 by Jim U

I need to add additional zone to my hot water system. To accommodate the room for an expanded header manifold can shorten my 2"black iron feedpipe by 18", which will lower my Taco scoop

making closer to the boiler then turn the 2" Black Iron back up giving me more room to expand the header.

I didn't know if the scoop needed to be at the same height as feed manifold.
Jim U

On 2018-01-27 by (mod) - proper location for the air scoop at a hydonic heating boiler

The air scoop needs to be at a local high point over the boiler. There are recommended distances and locations that depend on the model and type of air separater "air scoop" that you have installed.

See the examples and installation sketches in this Taco Air Separator installation guide

https://inspectapedia.com/heat/Taco-Air-Separator-Installation-Manual.pdf

On 2018-01-27 by Jim U

I need to add additional zone to my hot water system. To accommodate the room for an expanded header manifold can shorten my 2"black iron feedpipe by 18", which will lower my Taco scoop making closer to the boiler then turn the 2" Black Iron back up giving me more room to expand the header.

I didn't know if the scoop needed to be at the same height as feed manifold.
Jim U

On 2017-11-07 by (mod) -

Greg,

Indeed you're correct to be careful about the pressure temperature relief valve.

The risk would be that you open it and it spits out a piece of an internal washer or gasket and then continues to leak. We've written articles about dealing with that problem but my best suggestion is that if you have trouble with the valve you can post a comment or contact me directly by email using the page bottom contact like I'll be glad to give some advice.

On 2017-11-07 by Greg

Thanks! I was a bit reluctant to disturb the PRV but will try it that way.

On 2017-11-07 by (mod) -

You might find it more effective to release boiler air through the relief valve until you start to see water discharge there.

That will fill the boiler and vent air much more rapidly than through the tiny air vent that you're describing. What you got the boiler nearly filled and most of the air out the remainder might vent out through your air scoop and air vent as you described.

On 2017-11-06 by Greg

I need to install a new boiler drain valve on my Burnham (gas hot water) boiler and, as I do not want to drain the whole system, I plan to isolate the piping loop into and out of the boiler (close the relevant valves) and drain only the minimum amount of water out of the boiler to permit removal of the existing defective drain valve and install a new one.

My question is this: when I refill the boiler, will the Maid O' Mist 67 auto vent near the PRV eliminate air which enters the boiler with the refilling if the cap screw is left in the open position, or do I need to depress the Schrader valve beneath the cap to purge the air until the boiler is up to 15 psi?

Or...any other simple way of eliminating air before cranking up the boiler and circulating through the radiators. I'm trying to avoid having to purge air from individual radiators after this simple valve replacement. Thanks for your help.

On 2017-11-06 by Greg

I need to install a new boiler drain valve on my Burnham (gas hot water) boiler and, as I do not want to drain the whole system, I plan to isolate the piping loop into and out of the boiler (close the relevant valves) and drain only the minimum amount of water out of the boiler to permit removal of the existing defective drain valve and install a new one.

My question is this: when I refill the boiler, will the Maid O' Mist 67 auto vent near the PRV eliminate air which enters the boiler with the refilling if the cap screw is left in the open position, or do I need to depress the Schrader valve beneath the cap to purge the air until the boiler is up to 15 psi?

Or...any other simple way of eliminating air before cranking up the boiler and circulating through the radiators. I'm trying to avoid having to purge air from individual radiators after this simple valve replacement. Thanks for your help.

On 2017-10-21 by (mod) -

Mike

Take a look at THERMOCOUPLE REPAIR / REPLACEMENT - https://inspectapedia.com/heat/Thermocouple_Replacement.php

as if the burner doesn't ignite or stay lit I suspect a problem isn't the valve but the thermocouple.

There may be a separate problem with your "no heat" complaint. You already suspected that the system could be air bound. Sometimes we think we've bled problem air but we missed air that was trapped, for example in a horizontal run of piping.

If the circulator is working you'll feel the pipes get quite hot on the outlet end and after maybe 5 minutes you'll feel warm water returning on the circulator inlet side. If the inlet side stays cold I suspect either an air blockage or a circulator pump that's not running.

On 2017-10-21 Hart & Crouse gas boiler Model 4GP4

by Mike

I have a 40 year old (or more) Hart & Crouse gas boiler Model 4GP4 which has worked great. Two months ago Natl Grid shut the gas off to install a new meter but never re lit the pilot (I alway have the pilot lit) which I was unaware of until I turned the thermostat up the other day and no heat.

I looked at the boiler saw the pilot was out, re lit it but now when I turned up the thermostat the burners do not come on no heat. I bled everything that I know of to eliminate air blockage and still nothing. The Honeywell gas valve is different from the regular pilot, on, off settings on new models.

The only settings on this valve are Man, Auto, Manual and Opener. The valve was set to Opener but the burners do not come on. When I turned the valve to Auto the burners kick on but the boiler temperature gets really high and still no heat. I do not hear the circulator making any noise. Could that be the problem? Thank you, Mike

On 2017-10-21 by (mod) - turned out my aquastat was too high

Thanks for the comment, Kevin Terry. Can you suggest why a high aquastat setting would be involved in a problem with failure to eliminate air from a hydronic heating system? I ask because many heating systems run at a high of 200F and just under 30 psi of pressure when hot and do not suffer an air problem as a result, so I suspect something else was going on in your case.

On 2017-10-21 by kevin

@Terry K,
i had same problem changed both pressure relieif and expansion tank to no avail turned out my aquastat was too high turned it down a bit and all was good

On 2017-09-01 by (mod) - air scoop has a working air vent

Chris,

As long as the air scoop has a working air vent you should be OK.

That air scoop mounting point is a convenience, not a requirement.

On 2017-08-30 by Chris H.

Most scoops call for attaching a diaphragm expansion tank (actually just provide a little picture) to the bottom portion of the scoop. I already have an expansion tank that comes out the back of the boiler. Can I keep my tank at that location or do I need to move it to the air scoop location?

Thank you in advance.

On 2017-02-11 by (mod) -

Terry

Search InspectApedia.com for RELIEF VALVE LEAKS to see the common causes and cures, as there are several different causes that could be at work.

No, there won't be "too much water" if you are not seeing air at the air scoop. It means that there was simply not air present at that point in the system.

To drain the expansion tank search InspectApedia for EXPANSION TANK DRAIN to see details.

On 2017-02-11 by Terry K

I have a Laars Mini therm boiler system which has started to occasionally leak from the pressure relief valve. I replaced the relief valve, thinking the spring had weakened over the years. Same problem.

The Laars book says that a water-filled expansion tank may cause relief valve leakage.

But, the small circular tank does not have a drain option, and all pipework is soldered. I popped the cap off from the "air Scoop" and depressed the valve, and water flowed , so no air there, but, possibly too much water?

How would I drain the water from the expansion tank, short of de-soldering the unit?

Thankis

On 2016-02-19 by Bill

Danjoefriedman, thanks and that is a good route to go if nothing else pops up as a good trick. I like it better than adding a Coupling (total of 3 solder & joints vs. 2)

On 2016-02-19 by (mod) -

OK so when soldering, to protect equipment or devices on the hot side of the joint, wrap a wet rag around the protected device close to the fitting being sweated.

On 2016-02-19 by Bill

Oops, that was me with the last comment and spelling issues and not "Anonymous' about the instructions, thread first, solder second..

On 2016-02-19 by Anonymous

I have read the instructions on line and there is no indication about installing other then position: This Way Up, Flow This Way. If was a new system install, no issues b/c I could put the Adaptors on 'stubs' coming off the Scoop that go to the next fitting.

But retrofit? When I actually get the Scoop, I'll inspect, but even if 100% cast part, still concern over the thread sealant getting burnt if tread first, solder second. Have to rip it apart if it leaks... Of course I have head of lots of concerns over leaking Unions as well... So hoping someone may offer a 'trick of the trade'..

On 2016-02-19 by (mod) -

Very good question, Bill. I don't know. I would take a look at the paperwork that comes with the air scoop. They'll warn you about heat damage concerns during installation. Let me know what you see.

On 2016-02-18 by Bill

I will be replacing my older Amtrol EX- 30 Hydronic Expansion tank and would like to retrofit it with the combination Package that includes an Air Scoop and Air Vent. Since the Air Scoop is threaded cast iron I need to obviously sweet on a couple of copper Male Adaptors onto the pipe so I can in turn thread on the Scoop.

My question is: can I thread the Male Adaptors into the Scoop and then solder the Adaptors to the existing pipe?

I am unsure if there is anything in the scoop that may get heat damage or perhaps I will not get a good thread seal since any Teflon tape, etc. may get burned up in the sweating process.

I suppose the other choice is to install a Union, but in a number of pictures I have seen on what look like retrofit jobs, I do not see any Unions. Any advice is appreciated. Thanks

On 2016-01-28 by norrracing

Blead expansion tank now I need water in boiler tank. I lifted the bar on the valve to let water in but no water was let thru into boiler. Do I need to shut off the valve that lets domestic water into that valve with?

On 2016-01-28 by Ronald. Barbus

Blead water from old style expansion tank and now I need to add water to boiler ta

On 2015-11-26 by (mod) -

I don't think this is the right approach, Derek. Instead search InspectApedia for AIR DISCHARGE AT FIXTURES to read some advice.

My view is that it's better to find and fix the cause than to just address the effects.

On 2015-11-26 by derek winstanley

we are having major air issues in our hot water heating system. was looking for ideas and saw that the ias might work. the piping is 3" copper and I was wondering what to install and how to pipe it in ??

On 2015-03-26 by (mod) - Spirovent air eliminator installation instructions

Mosley I'd need to see the system and its piping to have a confident opinion but you're probably OK. Often the installer will put the feed where it's convenient from a plumbing view. The sequence you described is pretty standard.

The Spirovent air eliminator installation instructions show a sketch with the water supply incoming at a tee between an expansion tank and the bottom of a vent at the boiler. But that's not as critical IMO as the company's remarks that pertain specifically to the Spirovent location itself:

"The Spirovent Junior Air Eliminator should be installed at the point of lowest solubility in thesystem: that being where the temperature is the highest (i.e. after the boiler and/or heat
exchanger) and the pressure is the lowest (i.e. before the pump suction), as pictured in Figure 1below.

As with all hydronic system piping it is recommended to have the expansion tank
connection to the system on the suction side of the pump or circulator. " - www dot spirotherm dot com

On 2015-03-26 by Mosley

Where should the water supply for my boiler be going to? Currently the water supply goes to the boiler system return, the same port that all my zones return to.

water supply --> ball valve --> backflow preventer (Watts 9DM3) --> boiler autofill valve/pressure reducer (Taco 329-3) --> boiler supply

But as per the boiler manual, the Spirovent air eliminator manual and a few things I've found on your site and the internet, the water supply should be going between the bottom port of the Spirovent air eliminator and the expansion tank, the boiler system supply.

Is the current condition bad? Should it be corrected?

Question: when to replace the air separator

(Aug 21, 2011) john said:
my 30yr old boiler is being replaced do i need to replace taco air scoop?

Reply:

John I don't see any reason to replace the air scoop unless it's corroded or clogged.

Question:

(Jan 28, 2012) Don said:
I need to replace the air vent thats mounted on top of the air purger. Can I just turn off the pump to change it, or do I have too drain the system?

(Nov 15, 2012) Paul Eckerson said:
I have a process that is mixing a powder that increases the water's viscosity and also in-trains air and pumps it into an 1 1/2" pipe. I'm looking for a trap and automatic purge valve with 1 1/2 pipe female fittings to put inline to remove the air. You can call me @ 402 890 7361 to discuss appropriate solutions.

Question: Should the air purger on top of the taco air scoop remains open or closed?

Feb 17, 2014) Joe said:
Should the air purger on top of the taco air scoop remains open or close?

Reply:

Joe, unless the air purger is leaking water we leave the cap loose or unscrewed a turn or so on most models; there are a few air purge devices that have more precise outlet controls.

Question: how to change the air vent

(Feb 18, 2014) Anonymous said:
how to change air vent on air purger

Reply:

Anon:

To change an air vent or purger the steps required depend on what device is being replaced and where it is located.

At the top of this page under the article title you'll see a link to a closely-related article: AIR BLEEDERS - reading there you'll find a series of details on where air bleeders are located and how they are repaired or replaced.

For an air-scoop device like the ones discussed in the article found on this page you would have to shut down the heating system, let the system cool down, drain it, and use normal plumbing procedures to remove and replace the old air scoop device from the heating system piping.

Following replacement of a device like this one that requires draining the heating system piping (it's not necessary to drain the boiler or other components that are LOWER than the air purger/air scoop) you will have an air bound heating system so it will usually be necessary to manually force air out of the systems. InspectApedia sports articles on several methods to do that - fixing AIRBOUND HEAING SYSTEMS.

For just replacing a simple air vent like the ones at AIR BLEEDERS it is often possible to work carefully, removing and installing the new unit with just a minimum of spillage, and without having to drain the system, though letting it cool is important to avoid getting scalded, and dropping system pressure can make the squirt and leak problem more manageable.

Question: isolating zone valves vs draining the boiler

Oct 9, 2014) Anonymous said:
we need to change a zone valve. we can isolate one side of the zone valve with a valve will the air purger work as a check valve to isolate that from the other side? or do we have to drain the whole system?

Reply:

Anon

Not for air purgers I've seen. That valve does not include a shut-off in the water line.

Sometimes a flow control valve at the boiler can be closed to act as the second shutoff. But

Your plumber may need to install a second shutoff, or may need to drain and re-fill the piping, purging air after that

...

Continue reading at AIR SCOOPS SEPARATORS PURGERS - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• AIR BLEEDER VALVES
• AIR-BOUND HEATING SYSTEMS
• DISSOLVED OXYGEN DAMAGE CONTROL - use of bulk air eliminators on hydronic heating systems helps avoid damage from dissolved oxygen

Suggested citation for this web page

AIR SCOOPS SEPARATORS PURGER FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING RADIATORS

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