# Air Vent On A HW Circulating System



## Tommy plumber (Feb 19, 2010)

Widdershins said:


> If the pump should go points up, which does happen from time to time, it's going to be very, very, very loud. It's also quite capable of being an ignition source for a fire.


 
I have had some pumps that were chattering quite loudly. Usually an air lock. While we're on the subject, why don't more plumbers install an air vent on a re-circ line? Like on a radiator for a steam heating system which removes the air from the radiator but holds in the steam.


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## plbgbiz (Aug 27, 2010)

Tommy plumber said:


> ...why don't more plumbers install an air vent on a re-circ line?....


Honestly I've never seen a circ line with an air vent but it seems like it is worth discussing.


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## rjbphd (Feb 5, 2010)

plbgbiz said:


> Honestly I've never seen a circ line with an air vent but it seems like it is worth discussing.


 You NEVER need air venting of any kind if the system is piped correctly!! The highest point of the re circ line should be the shower valve, hence when opened.. the air will be removed before being in service. I've done many re circ jobs without using the pump, incudling ranch homes.


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## futz (Sep 17, 2009)

The manual of a recent circ pump I installed asked for an auto air vent. I thought, "Hmm... Never put one before...", and didn't put one on. Had to do the usual small fight with it to get the air out (loosened the cap of the check valve and let it bubble for a while), but not a big deal. Once the air is out they never seem to lock up again.


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## rocksteady (Oct 8, 2008)

rjbphd said:


> You NEVER need air venting of any kind if the system is piped correctly!! The highest point of the re circ line should be the shower valve, hence when opened.. the air will be removed before being in service. I've done many re circ jobs without using the pump, incudling ranch homes.


How does that work with overhead piping? 


I've seen a few air vents around here on recirc. lines but I can't remember seeing any recirc. lines without air vents that were air locked. It sounds like a good idea but in my experience, doesn't seem necessary.






Paul


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## ZL700 (Dec 8, 2009)

You already have an auto air vent installed, its every fixture when you open it


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## BROOKLYN\PLUMB (May 21, 2010)

ZL700 said:


> You already have an auto air vent installed, its every fixture when you open it


For real


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## Bellboy (Jan 21, 2012)

I've installed an air vent on looped systems for floor heating before. That's the only time I ever used one on a house. Used them a lot in commercial work though.


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## BROOKLYN\PLUMB (May 21, 2010)

Bellboy said:


> I've installed an air vent on looped systems for floor heating before. That's the only time I ever used one on a house. Used them a lot in commercial work though.


I believe were discussing it on domestic hot water not heating closed loop


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## OldSchool (Jan 30, 2010)

Never in my entire days have I used an air vent on a return line...... Never been a problem

Like ZL700 says every hot tap or outlet would be a vent

Not only that.... The water should never have a problem circulating as once the HW is not in use the only place it is forced through would be the return line

Sent from my miniature laptop


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## Widdershins (Feb 5, 2011)

BROOKLYN\PLUMB said:


> For real


I've seen air bubbles/pockets in clear pex circulating loops months after the system was initialized, most always in high spots.

I looked into installing a Spirovent rated for high pressure systems on a system earlier this year because of excessive hammering in a Tempress II pressure balanced shower valve we installed during a remodel.

There was definitely air in the lines, but the problem turned out to be something else altogether -- Some idjit during a previous remodel had put a PRV on the cold water line feeding the HWT in a wall box that had a framed picture in front of it -- We figured out that the domestic HW pressure was 25psi lower than the cold water supply and that the pressure balancing valve couldn't keep up with the pressure differential. Once we eliminated the PRV the hammering went away.

We never did get around to installing the Spirovent, but at the time I thought it was a very good solution to the visible air pockets in the return line.


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## Widdershins (Feb 5, 2011)

Tommy plumber said:


> I have had some pumps that were chattering quite loudly. Usually an air lock. While we're on the subject, why don't more plumbers install an air vent on a re-circ line? Like on a radiator for a steam heating system which removes the air from the radiator but holds in the steam.


You sure it wasn't the check valves chattering? I've had to replace several defective Legend spring checks that chattered and rattled every time there was movement in the system.

I think part of the problem with sweat spring checks is that excessive heat while soldering weakens the return spring. Proximity to the circulating pump might also be a factor.


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## BROOKLYN\PLUMB (May 21, 2010)

Widdershins said:


> I've seen air bubbles/pockets in clear pex circulating loops months after the system was initialized, most always in high spots.
> 
> I looked into installing a Spirovent rated for high pressure systems on a system earlier this year because of excessive hammering in a Tempress II pressure balanced shower valve we installed during a remodel.
> 
> ...


I don't doubt that air gets in the lines, just have never seen it (cause of copper) lock up a pump. Maybe if the pump was located at the highest level. 
I have never seen anything other than a hosecock for initial bleed/drain down never an auto vent 

Are spirovents potable? I am a fan they work really well!


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## Widdershins (Feb 5, 2011)

BROOKLYN\PLUMB said:


> I don't doubt that air gets in the lines, just have never seen it (cause of copper) lock up a pump. Maybe if the pump was located at the highest level.
> I have never seen anything other than a hosecock for initial bleed/drain down never an auto vent
> 
> Are spirovents potable? I am a fan they work really well!


They make a model specifically designed for high pressure domestic systems. Nobody carries it on their shelf, of course. Special/Factory order only in my market.:laughing:

Back to the OP -- Tommy raises an interesting point.:thumbsup:


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## rjbphd (Feb 5, 2010)

Widdershins said:


> I've seen air bubbles/pockets in clear pex circulating loops months after the system was initialized, most always in high spots.
> 
> I looked into installing a Spirovent rated for high pressure systems on a system earlier this year because of excessive hammering in a Tempress II pressure balanced shower valve we installed during a remodel.
> 
> ...


Spriovent are not made for this situtation.. piped in corrected and use pre charge air chambers would solved this problem.


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## bizzybeeplumbin (Jul 19, 2011)

I have seen the same, air bubble next to the pump in clear pex, no circ. Problem solved with a hose bib at the pump and a hose connected for 5 minutes. No problems unless the line is cut or water is turned off. Simply prime pumps again. really no big deal.

Paul, if you pipe the return to the highest point in the house, or attic and down to the water heater drain the water will circulate itself. Almost like a siphon. It will pull itself around the loop. There is a name for it but I can't think of it right now.


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## OldSchool (Jan 30, 2010)

bizzybeeplumbin said:


> I have seen the same, air bubble next to the pump in clear pex, no circ. Problem solved with a hose bib at the pump and a hose connected for 5 minutes. No problems unless the line is cut or water is turned off. Simply prime pumps again. really no big deal.
> 
> Paul, if you pipe the return to the highest point in the house, or attic and down to the water heater drain the water will circulate itself. Almost like a siphon. It will pull itself around the loop. There is a name for it but I can't think of it right now.


Yah ... its called convection


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## pilot light (Apr 21, 2012)

I install a flush bib and then flush the recirc on start up!


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## Tommy plumber (Feb 19, 2010)

futz said:


> The manual of a recent circ pump I installed asked for an auto air vent. I thought, "Hmm... Never put one before...", and didn't put one on. Had to do the usual small fight with it to get the air out (loosened the cap of the check valve and let it bubble for a while), but not a big deal. Once the air is out they never seem to lock up again.


 






On a solar panel install, among other things, an air vent is needed.


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## Tommy plumber (Feb 19, 2010)

Take a look...(sorry for the bad pic, I had a little trouble uploading this .pdf document. Had to take a pic, re-size it through pix-resizer software, then up load.)

But the point is, a solar water heating system is essentially a hot water re-circulating line. And an air vent is recommended. A solar system is different, I know, from a regular hot water re-circ, but I still think it's a good idea to have an air vent.


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## rjbphd (Feb 5, 2010)

Solar heating and panels are not in the same ball game with hot water rec line from the highest plumbing fixture return to water heater. As I said before, don't need vent or pump if its piped correctly.


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## Affordable (May 22, 2012)

Tommy plumber said:


> I have had some pumps that were chattering quite loudly. Usually an air lock. While we're on the subject, why don't more plumbers install an air vent on a re-circ line? Like on a radiator for a steam heating system which removes the air from the radiator but holds in the steam.


But tommy i have never done that or seen that in my times.. how ever it is something worth lookin into but wouldnt the re-circ into the hotwater heater be like a air chamber and the opening and close the fixtures etc.? i don't know but im gonna look into that.. cause still there is air chambers already on the supplys in the walls .. atleast there should be.


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## rjbphd (Feb 5, 2010)

Affordable said:


> But tommy i have never done that or seen that in my times.. how ever it is something worth lookin into but wouldnt the re-circ into the hotwater heater be like a air chamber and the opening and close the fixtures etc.? i don't know but im gonna look into that.. cause still there is air chambers already on the supplys in the walls .. atleast there should be.


 Air chambers are one of the most useless piece of dead end pipe after 3 weeks being in service.


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## Affordable (May 22, 2012)

not exactly cause i have seen houses where u would hear that thump cause there was no chambers. Yet after the chambers put in they were fine .. but sometimes its not about the chambers its about how far apart they put the hangers cause if u put them far apart they will tend to make a lil thump... in some cases :thumbup:


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## intohotwater (Feb 10, 2012)

If the boiler room is on the top floor of a 20-30 story building the return line to the hot water tanks have no take offs to the suites and when the system is drained for repair it will get air locked. I just installed a hose bib by the recirc pump on the top floor and bleed all the air out. Once it's flowing it works. Putting an air vent close to the suction side of a pump will pull Ir into the system. Putting an air vent close to the pressure side and the air vent may not open to let put air.


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## Joeypipes 23 (Feb 2, 2011)

rjbphd said:


> You NEVER need air venting of any kind if the system is piped correctly!! The highest point of the re circ line should be the shower valve, hence when opened.. the air will be removed before being in service. I've done many re circ jobs without using the pump, incudling ranch homes.


As a rule of thumb you should tee off the hot water below the last floor and run it back? Or am I completely wrong


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## rjbphd (Feb 5, 2010)

Joeypipes 23 said:


> As a rule of thumb you should tee off the hot water below the last floor and run it back? Or am I completely wrong


 Run your hot water to the highest fixture of the floor, shower valve and then runs the return from there.


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