A lot of air in hydronic sysytem


Old 12-17-17, 01:27 AM
Thread Starter
Join Date: Dec 2017
Location: United States
Posts: 1
Received 0 Votes on 0 Posts
A lot of air in hydronic sysytem

I haven't purged my system in many years... just drained my expansion tank that was waterlogged (not the membrane type, old style tank which is in great shape); A lot of air got into the second floor radiators and I want to do a complete water flush out of my system...... [size=2]my system [/size]http://i.imgur.com/NrHwI1A.jpg....... My line in is above the hose connection flush valve on the return.... so if I turn off the return valve just above the circulating pump and boiler, I will have water coming in from the line in pressure reducing valve and directly out of the flush valve......what sense does it make that the LINE IN is directly above the flush valve on the return????? only getting 10psi???? Thanks for any help..... Also says my style expansion tank should have some water in it???? how the hell do I know how much water is in this old style tank.......which is connected to a huge gravity control WATTS 2000 flow valve????
Sponsored Links
Old 12-17-17, 02:03 PM
Join Date: Oct 2013
Location: United States
Posts: 2,998
Received 50 Votes on 47 Posts
pics would be very helpful.

As far as the water in your expansion tank when you pressurize your system water will automatically go into the tank and seek it's own level. As long as you have room in that tank for when the water is heated and expands your good.

If over time it gets waterlogged again you will know it because your boiler pressure will rise when heated because the water has no place to go so when the boiler gets to 30psi your relief valve will let go to relieve the pressure.

That's the time you will have to drain it.

A word of caution when draining these conventional tanks. They must be completely drained and not just what you think is enough.

If not totally drained it will fill right up again and you will have worse problems than before.

Hope this helps a little.
Old 12-17-17, 02:59 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 59,129
Received 1,113 Votes on 1,033 Posts
Welcome to the forums.

A complete flush sounds like a great idea but it's not. Every time you open the system.... the air must be removed from the new water. The system should only be opened in case of repair. .......... How-to-insert-pictures
Old 12-17-17, 05:12 PM
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 35 Votes on 27 Posts
Thank you for posting in the open forum. I apologize if I came across rude or uncaring in my response to your private message.

The only picture you have shown is the nameplate of the boiler. While it does contain certain important information what we really need at this time are several well lit and in focus pictures of the system. Pictures need to be from far enough back (or wide angle lens setting) to allow us to see how the various parts are connected. If we need additional close-up pictures we will ask for them.

Generally speaking it is not advisable to "flush" a hydronic heating system. This is because the worst thing in a hydronic system is oxygen, from air, that causes corrosion. When a system is heated to operating temperature most of the oxygen is driven out of solution and either expelled through air vents or, in the case of a "old fashioned" compression/expansion tank (what you describe having) is directed to the tank to provide a cushion for expansion of the water. Flushing and refilling the system brings in a lot of air that is dissolved in the new water.

The one exception to not flushing is when the system has huge amounts of dirt and other foreign materials. Otherwise it should never be necessary to flush the system. Nor should it be necessary to "purge" the system or otherwise try to remove the air. If the system was properly piped the air will eventually be returned to the expansion tank.

Spott gave you good information. It is not always necessary to completely drain the expansion tank in order to get the proper air cushion but it takes a bit of specialized equipment and a specific procedure.

Please post the pictures I have requested and tell us of any specific problems you are experiencing.
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: