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Baseboard Heating

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Question Topic

Baseboard Heating Purging Air

The Home Wizard app calculates your ideal home care program to avoid problems with your Baseboard Heating, but sometimes trouble can still occur. Here are answers to questions about baseboard heating purging air.

QUESTION FROM Jeff

I have a 3 zone heating system in my home.1 zone in my family room,2nd in my kitchen/dinning/living room and a 3rd that heats the upstair bed rooms.My house is 30 yrs old and im sure that it hasn't been bleed.The 1st and 2nd zones seem fine you get your normal crinkin/crackin noises when it stars up then goes away but on the 3rd zone you can actually hear the water flow threw the baseboards sounds like a little river running.Does this mean it has air in the system?If soo can you explain how to bleed it?I know it overdue for this.Thankyou very much in advance..

ANSWER FROM HOME-WIZARD

Dear Jeff:

Yes, it does sound like the piping of your third heating zone on your baseboard heating system has air trapped in it, and that it needs to have the air purged out of this line.

Regarding the procedure for purging air from a baseboard heating zone, it will depend on your specific configuration of valves, etc. But in general, here is the procedure for purging air from a baseboard heating system.

First, I would suggest heating system cool down before purging the air out of the system. There are two reasons for this: 1) as the water cools down, dissolved air in it will be released from the water, which will then allow you to purge this air out as well; and 2) less risk of being scaled by hot water. However, if it is not practical for you to let your system cool completely down, then you can still purge the system, but just be careful of the hot water.
Second, you should locate your hot water heating system's back-flow preventer valve. This is the valve that comes off of your main household supply line, and it prevents water from your heating system from flowing backward into your household supply. It typically looks something like the one pictured here with a release lever on top:

http://www.blueridgecompany.com/radiant/hydronic/517/watts-fill-valve-and-backflow-preventer

Then as I mentioned above, the exact procedure for specifically which valves to open and close as you are purging your baseboard heating system of air will depend on how your specific system has been piped. But in general, you will then want to:

1) turn off your boiler and heating system.

2) make a note of which valves are open, and which are closed.

3) close the valves that allow you to isolate your boiler from the rest of the system (so that you don't get a pressure spike that causes your boiler's pressure relief valve to lift, as this weakens it).

4) connect a drain hose to safely drain hot water from your system to a floor drain, or to outside. Be CAREFUL, as the water coming out can be scalding HOT.

5) follow your pipes around starting with your backflow-preventer valve, and open only those valves necessary to allow the fresh water that is coming into the system from the backflow-preventer valve to flow through the particular loop that you are trying to purge (that is, one loop at a time), and then flow out the drain hose that you have connected. Then if you look at your back-flow preventer valve, the small lever on the top of the valve operates the bypass for the pressure reducer for the valve. So as you lift up on the lever, it opens the valve to street pressure from your water supply. So as you start to purge the water from one of your heating system loops, you can lift the lever to increase the pressure to get stronger flow to the line that you are trying to purge. But let the lever down if the pressure in your system starts to go too high (however, if you isolate you boiler properly, as described below, then you won't have to worry about over-pressuring your system).

6) close all of the valves, and then repeat opening the valves needed to purge each loop.

7) disconnect the drain hose and close this valve.

8) return all of your valves to their original position (especially the valves that you used to isolate your boiler).

If you have turned off your boiler and heating system, and then properly closed the valves to isolate your boiler, and properly placed your drain hose to a drain or outdoors, then you can fairly safely purge your system without hurting your boiler or scalding yourself.

And when you go to start you system back up, you of course just need to be sure to put the valves back to their original positions.
Since you have isolated your boiler from the purgingBut this is a relatively small area compared to your entire system, and the benefit to isolating it, is that you don't need to worry about over-pressuring your boiler while you are doing the air purging.

Also, here are is an additional suggestion that you might find helpful. If you haven't had your annual inspection done yet on your boiler, then when the service technician comes out to do your inspection and service, you can ask them to show you exactly how to purge your specific system, when they can be physically there to point out which of your valves does exactly what.

Hope this is helpful.
Home-Wizard.com

QUESTION FROM sandi in Ct.

How do you refill an empty baseboard? Our pipe burst and my husband replaced the pipe and baseboard. We have a auto refill but it is now day 2 and it s very slow in circulating in that zone. We have a 2 zone system and the other zone is fine. The PSI is where it should be on the furnace.

ANSWER FROM HOME-WIZARD

Dear Sandi in CT:

Have you tried purging the air out the piping for the zone that is not working as well?

Regarding the procedure for purging air from a baseboard heating zone, it will depend on your specific configuration of valves, etc. But in general, here is the procedure for purging air from a baseboard heating system.

First, I would suggest heating system cool down before purging the air out of the system. There are two reasons for this: 1) as the water cools down, dissolved air in it will be released from the water, which will then allow you to purge this air out as well; and 2) less risk of being scaled by hot water. However, if it is not practical for you to let your system cool completely down, then you can still purge the system, but just be careful of the hot water.

Second, you should locate your hot water heating system's back-flow preventer valve. This is the valve that comes off of your main household supply line, and it prevents water from your heating system from flowing backward into your household supply. It typically looks something like the one pictured here with a release lever on top:

http://www.blueridgecompany.com/radiant/hydronic/517/watts-fill-valve-and-backflow-preventer

Then as I mentioned above, the exact procedure for specifically which valves to open and close as you are purging your baseboard heating system of air will depend on how your specific system has been piped. But in general, you will then want to:

1) turn off your boiler and heating system.

2) make a note of which valves are open, and which are closed.

3) close the valves that allow you to isolate your boiler from the rest of the system (so that you don't get a pressure spike that causes your boiler's pressure relief valve to lift, as this weakens it).

4) connect a drain hose to safely drain hot water from your system to a floor drain, or to outside. Be CAREFUL, as the water coming out can be scalding HOT.

5) follow your pipes around starting with your backflow-preventer valve, and open only those valves necessary to allow the fresh water that is coming into the system from the backflow-preventer valve to flow through the particular loop that you are trying to purge (that is, one loop at a time), and then flow out the drain hose that you have connected. Then if you look at your back-flow preventer valve, the small lever on the top of the valve operates the bypass for the pressure reducer for the valve. So as you lift up on the lever, it opens the valve to street pressure from your water supply. So as you start to purge the water from one of your heating system loops, you can lift the lever to increase the pressure to get stronger flow to the line that you are trying to purge. But let the lever down if the pressure in your system starts to go too high (however, if you isolate you boiler properly, as described below, then you won't have to worry about over-pressuring your system).

6) close all of the valves, and then repeat opening the valves needed to purge each loop.

7) disconnect the drain hose and close this valve.

8) return all of your valves to their original position (especially the valves that you used to isolate your boiler).

If you have turned off your boiler and heating system, and then properly closed the valves to isolate your boiler, and properly placed your drain hose to a drain or outdoors, then you can fairly safely purge your system without hurting your boiler or scalding yourself.

And when you go to start you system back up, you of course just need to be sure to put the valves back to their original positions.

Since you have isolated your boiler from the purging process, this procedure will not purge air from this segment of your system. But this is a relatively small area compared to your entire system, and the benefit to isolating it, is that you don't need to worry about over-pressuring your boiler while you are doing the air purging.

Also, here are is an additional suggestion that you might find helpful. If you haven't had your annual inspection done yet on your boiler, then when the service technician comes out to do your inspection and service, you can ask them to show you exactly how to purge your specific system, when they can be physically there to point out which of your valves does exactly what.

Hope this is helpful.
Home-Wizard.com

QUESTION FROM Roy

1. Should I let my forced hot water heating system cool down before trying to purge the trapped air from the drainage spigots?

2. How do I manually manipulate the Watts self-feeding (auto-makeup) water valve to control pressure so it doesn't go above 25 PSI during the actual air purging process?

3. To purge air from a forced hot water system, you advised another homeowner to "close all of the shut-off valves" as one of the steps to follow just before opening the drain spigot to drain water from each heating loop. My heater has three shutoff valves: 1. the valve to shut all water off to the house, at the pump location 2. the shut-off valve just before the pressure regulating valve that is part of each heating loop 3. a shut off valve that supplies fresh water directly into the side of the boiler, labeled "cold water inlet". Do I shut all these shut-off valves off before I drain the water from each loop?

ANSWER FROM HOME-WIZARD

Dear Roy:

Regarding your first question, I would suggest letting your forced hot water heating system cool down before purging the air out of the system. There are two reasons for this: 1) as the water cools down dissolved air will be released from the water, which will then allow you to purge this air out as well; and 2) less risk of being scaled by hot water. However, if it is not practical for you to let your system cool completely down, then you can still purge the system, but just be careful of the hot water.

Regarding your second question, does your Watts auto-fill valve look like the one pictured here with the release lever on top:

http://www.blueridgecompany.com/radiant/hydronic/517/watts-fill-valve-and-backflow-preventer

If not, here is the contact information for Watts Valves: http://www.watts.com/pro/contactus.asp who can tell you specifically for your particular model of valve.

And regarding your third question, you mentioned that you are looking to drain your system, but do you mean actually draining the system, or just purging the air?

Home-Wizard.com

FOLLOW-UP FROM Roy

Hi again, and thanks for the advice thus far. In answer to your first question, my Watts fill valve looks exactly like the one pictured, with the release lever on top, at:

http://www.blueridgecompany.com/radiant/hydronic/517/watts-fill-valve-and-backflow-preventer

I just don't know how to operate the valve to regulate the water
pressure when purging the air from each forced hot water loop.

To respond to your second question, I am interested in purging the air from the system through the drain spigots. I am trying to accomplish this by flushing all of the water plus air out of the spigot for each heating loop, then filling each loop with fresh, but not too cold water, that hopefully has no new air in it. As noted in my question 3, I appear to have three shutoff valves to consider at the boiler.

After the spigot draining and new water fill-up is done, I plan to bleed air from the air vent in the system to get out any additional air that may be released.

Your thoughts in reply to my last two questions would be most
appreciated. Any source of very detailed steps as to how this draining and refilling procedure can most safely and effectively be accomplished would be most appreciated.

Thank you.

ANSWER FROM HOME-WIZARD

Dear Roy:

Regarding your first question, yes, it sounded like you had something like a Watts Fill Valve and Backflow preventer valve, and from what you've said, it turned out that the link I sent you was exactly the one you had. Great!

Then if you look at your valve, the small lever on the top of the valve operates the bypass for the pressure reducer for the valve. So as you lift up on the lever, it opens the valve to street pressure from your water supply. So as you start to purge the water from one of your heating system loops, you lift the lever to increase the pressure to get stronger flow as you are purging that line. But let the lever down if the pressure in your system starts to go too high (however, if you isolate you boiler properly, as described below, then you won't have to worry about over-pressuring your system).

Now regarding your second question, the exact procedure for specifically which valves to open and close as you are purging your baseboard heating system of air will depend on how your specific system has been piped. But in general, to be safe, you will want to:

1) turn off your boiler and heating system.
2) make a note of which valves are open, and which are closed.
3) close the valves that allow you to isolate your boiler from the rest of the system (so that you don't get a pressure spike that causes your boiler's pressure relief valve to lift, as this weakens it).
4) connect a drain hose to safely drain hot water from the system.
5) follow your pipes around starting with the Watts fill valve, and open only those valves necessary to allow the fresh water that is coming into the system from the Watts valve to flow through the particular loop that you are trying to purge (that is, one loop at a time), and then out the drain hose that you have connected.
6) close all of the valves, and then repeat opening the valves needed to purge each loop.
7) disconnect the drain hose and close this valve.
8) return all of your valves to their original position (especially the valves that you used to isolate your boiler).

If it helps you to think of it this way, if you have turned off your boiler and heating system, and then properly closed the valves to isolate your boiler, and properly placed your drain hose to a drain or outdoors, then you can fairly safely purge your system without hurting your boiler or scalding yourself.

And when you go to start you system back up, you of course just need to be sure to put the valves back to their original positions.

Also, here are some additional suggestions that you might find helpful:

First, if you haven't had your annual inspection done yet on your boiler, then when the service technician comes out to do your inspection and service, you can ask them to show you exactly how to purge your specific system, when they can be physically there to point out which of your valves does exactly what.

The other thought is that you can call the toll-free phone number for the company that manufactures your Watts valve. I've talked to them before, and they are very helpful regarding how to purge, backflush and drain baseboard heating systems where their valves are installed. And here is their toll-free phone number in Vashon, Washington: 866-361-4782.

Hope this is helpful.
Home-Wizard.com

FOLLOW-UP FROM Roy

Thank you so much for your very helpful and thorough advice!

I now feel comfortable that I will be able to safely purge the air from the forced hot water heating loops. Thank you also for the advice to get on-site advice during the annual inspection of the boiler. The contact to the Watts manufacturer is also a great lead.

You have been so much help to me! Your site is clearly the best, and I have been searching a long time through the Internet, and thus have a strong basis for a comparison!

Take care.

QUESTION FROM Chris carolan nj

I keep getting air in my system. Its a 4 zone system and only the top floor 1 zone gets it. I do have another zone on the top floor, but that one is always fine. I bleed it and then a month later it gurgles and sounds like a faucet again, so I bleed it and its good for another month. What is happening to be allowing air in? Thanks

ANSWER FROM HOME-WIZARD

Dear chris carolan nj:

If you keep getting air in your hot water heating system, it sounds like you might likely have a small water leak somewhere in your system. You should check all of the bleeder valves on your system, as this is a common place for water leaks to occur. And you should also check all of the piping, valves and fittings around your boiler for signs of water leakage. Hopefully, there are no water leaks occurring in any of the piping anywhere inside of your walls, as this can cause major problems related to pests, etc.

Hope this is helpful.
Home-Wizard.com

FOLLOW-UP FROM carolan nj

have hot water baseboard heat with only a bleeder valve on the boiler..I had a professional come out a month ago and he said it was just air and made the system work great but a month later its loud again i bled it today and it had alot of air but now its whisper quiet...No signs of leaks anywhere..All 3 other zones all are quiet and work great..just this one zone...

ANSWER FROM HOME-WIZARD

Dear chris carolan nj:
It sounds like you have a stubborn problem with air in one of the 4 zones of your baseboard heating system.
A couple of thoughts for things that you might want to check:
1) In the zone that you are having problems with, it sounds like it is on the second floor. Can you find any bleeder valves anywhere along this zone, where you can bleed the air out of this zone?
2) When you are bled your system using the valve at the boiler, was your boiler cold (that is, that it had been off for at least 3 hours)?
3) Are you able to bleed air out of the top of your boiler, for example through a pressure relief valve. Remember, always be very careful whenever you are bleeding air out of your heating system, as the water can be scalding hot.
Hope this is helpful.
Home-Wizard.com

FOLLOW-UP FROM Chris carolan nj

I did bleed the system hot not but was not running for 20 minutes..I did just open the zone valve and the drain and pushed the little lever to allow more water to rush in around 25 psi...you could hear the air coming out of it but its still running quiet day 2 as for any bleeders i haven't seen any on the baseboards thru out the house.....

ANSWER FROM HOME-WIZARD

Dear chris carolan nj:

Well I guess the good news is that your problem zone has been quiet now for 2 days.

If your system was only off for 20 minutes when you last bled it, then it probably had not had time to cool down completely. So if the problem comes back, then one option that you still have is to try to let your system cool completely down (off for at least 3 hours) before you bleed it.

And I assume that when you inspected the problem zone for leaks and bleeders, that you removed the baseboard covers to see if there were any bleeders that might have been hidden by the covers?

If you still have problems after trying the above, please let us know, and we'll try to figure something else for you.

Home-Wizard.com

QUESTION FROM pingber

I've been having problems with bleeding my hot water baseboard system. The tech has tried it twice, but it still gurgles in the lower floor zone when the pump kicks on and then again when the water reaches hot (around 170 or so). I noticed that if I carefully lift the boiler pressure relief valve, air escapes for a few seconds before water is released. I did this when the boiler was only warm, not hot. could this air be a source of my problem?

ANSWER FROM HOME-WIZARD

Dear pingber:

Yes, it does sound like your system has air trapped in it that still needs to be bled. When the technician comes out, you might also want them to confirm that your boiler is operating at a pressure of between 12-15 psi.

Hope this is helpful.
Home-Wizard.com

FOLLOW-UP FROM pingber

Hi and thanks for the quick reply.

The tech came out and noticed a few things. First, he was on the "install team" when this furnace was put in. He immediately reset the aquastat to 160 instead of 180 becuase he said that this furnace continues heating for about 10 degrees or so after the aquastat is "tripped" and at the time of the install, he felt that 190 was too high. Second, he set the circulator speed for medium instead of low (new circulator was put in last year, old one only lasted 1 year), 3rd, he bled the system again, this time from a COLD state, one loop at a time, then both loops together. FInally he set the pressure to about 19-20 psi. Everything seems fine this morning (that's why I'm writing so early ... I was up before the boiler kicked in).

What do you think?

ANSWER FROM HOME-WIZARD

Dear pingber:

It sounds like when they came back that the tech has done a nice job of properly adjusting your heating system.

A couple of thoughts. I assume that the technician is familiar with your particular system, and this is the reason that they set the pressure at 19-20psi, which otherwise seems a bit high.

Also, you mentioned that they bled the system of air when it was cold. It was good that they did this, as when the system is hot, more of the air can be entrained in the warmer water (which is why when you run hot water from the faucet in your sink that the hot water will look cloudy from the trapped air).

And 160 degrees is a good set temperature for your aquastat. It's not to high, which is good for energy efficiency; and it's not too low, which could risk Legionnaires disease.

So it sounds like you should be in good shape now.

Regards,
Home-Wizard.com

QUESTION FROM Christina

How do you remove air that is trapped in pipes of hot water base board heaters? I can't find any valves? I used to have radiators in my old home, and each one had a little valve on the side.

ANSWER FROM HOME-WIZARD

Dear Christina:

If you go to this webpage in Home-Wizard's Maintenance Library for baseboard heating systems:

http://www.home-wizard.com/maintenance/baseboardheating.asp

You will see a link for a tutorial video at the top. When you click on this link it opens a video which describes how your baseboard heating system works and its different parts. And then at about the 6 minute point of the video, it describes the procedure for how to purge air from your baseboard heating system.

Hope this is helpful.
Home-Wizard.com

QUESTION FROM Frustrated!!!

Hello. After having a "noise" in our gas furnace finally fixed, we now have what sounds like a stream flowing through our baseboards. The contractor fully bled the zones so I do not know why it is so bad there should not be air in the system. We had silence before this was done. He said becasue he put all fresh water in the system, it has oxygen in it and it will take about a week to get out. Is this true? It is driving me crazy. It is a 20 yr old system and it runs hot 180 - 200 deg. and he said he may have to replace some vents and gages if he comes back ($300 - $400). Why would this be doing this all of a sudden? All he really did was put sludge cleaner in the system after he purged it. this is such a pain!

Thank you

ANSWER FROM HOME-WIZARD

Dear "Frustrated":

Regarding your questions . . .

If in doing their recent work for you your service person drained a significant amount of water from your system, then yes, the fresh make-up water could release a lot of air when it is heated up by boiler and circulated through your heating system.

And yes, this air trapped in your system is likely what is causing the sound that you describe of a "stream flowing through your baseboards".

To fix this, you would need to purge this air out of each zone of your heating system. If you are comfortable doing it yourself, you can find the procedure for how to do this on our "Baseboard Heating System" webpage of our online Maintenance Guide:

http://www.home-wizard.com/maintenance/baseboardheating.asp

Without being able physically examine your heating system, however, it's difficult to determine why your service person needs to come back to replace some vents and gauges as you mentioned.

Hope this is helpful.
Home-Wizard.com

Other Topics

Baseboard Heating