How do I bleed my closed loop system?

Steve Scott

Sunday 12/07/03

I am a H.O. with basic knowledge of heating (enough to be dangerous, as they say!).

I was wondering if someone could tell me:
1. how to bleed my closed loop system. -and-
2. how do I fill it-more so, how much do I fill it.

It's a very small house with three levels (Basement, 1st, & 2nd floors). I have a three zone, gas fired, hot water baseboard system. I believe it is a single temp system(don't think there is any feedback of outside air temp to make water hotter when it's colder outside)

Zone 1-Single Loop-Basement

Zone 2-single loop-1st Floor

Zone 3-Split loop-2nd floor
The split loop (2nd floor zone) is split right above the boiler in the basement, so two supply's and two returns run all the way to the 2nd floor.

I can not find *any* bleeders on any of the baseboards at any level. I have checked every single one of them, looking closely at each end, as well as the middle. I assume bleeding is done in the basement from the valves near the 3 pumps, but I need to learn the procedure.


The problem at hand is that, this morning my wife and I woke up to air bubbles & water sloshing sounds in the two back bedroom baseboards in the rear half of the 2nd floor. When I feel the rear baseboards, they're just luke warm. I am assuming that only one side of the split loop has air, since the front side of the 2nd floor (sm front bedrm & Bath) is not making the noise nearly as much as the front.

So I need to know how to go about getting the air out.

The other problem, getting water back in? I see the mushroom looking device near the expansion tank. When I pull on the handle, it seems to let water in the MAIN Heater LOOP. How do I direct it just to the loop needed?

Also, I see two other small valves, one on each side of the split loop. I belive they are those (I don't know what the proper name is) check valves that stop the natural heat flow of water, when the loop should be off.

I believe there is only one pressure meter on the side of the heater. Is there a range it needs to be in?

My apoligies, up front, to the pro's saying "Uh oh, another DIY H.O. But, unfortuatly, I dont live above the Merritt Pkwy, I live on the post rd, you who are in the area, know what I mean!! l.o.l.

One other thing, does this type of problem ever "right itself"? If the sound starts to go away, does this mean it's correcting itself? or does this mean there is no water left in that zone...I guess I would know by feeling the baseboard.

I look forward to your return posts. I was very impressed with this site and have learned a lot so far.

Thanks,

Steve Scott
Greenwich, CT 06830
sescott@ix.netcom.com

Mike T., Swampeast MO

With a multi-loop system there should be some way to isolate each loop in turn, introduce water at one end and remove air at the other. Ideally, the "split" loop should have some way to isolate one side from the other, but sometimes things seem to be installed on the premise that problems will eventually "right themselves". Remember you also have to ensure that the boiler and mains themselves are emptied of air and that the compression tank is properly charged with air on one side and full of water on the other.

Honestly, I'd pay for a good long service call to show you how to properly drain and fill your system. Some might consider this "too much knowledge" for a "typical" homeowner however. Personally I think it would be very nice if contractors left drain/fill sequence instructions posted by all but the most simple systems. If YOU encounter a bleeding "trouble spot" the next person probably will as well and why make them re-learn what you already had to figure out...

Piping and electrical schematics would be nice as well... Both GREATLY assist trouble-shooting down the road.

John@Reliable_5

Steve,this might help?

Look on the return lines,there should be 1 shut off on each zone and a drain valve before it, if so shut off 1 at a time and then open drain valve into bucket or use a hose, the "mushroom" devise is a pressure reducing valve which will add water to proper pressure automatic @12 to 15 psi cold, drain zone of 15 to 20 gallons and close back up and do other zones like above, The above is a common set-up but plenty of other ways to pipe a system so it may not look anything like I said. If this dosen't make sense call your service company for help. John@Reliable

Mark Wolff

Boiler Air Bleeding

First, shut off all zones except the one with air, supply and return pipe. Then shut the return valve only on the one with air, and open the boiler drain located before the valve. Run that zone until you get scalding hot water (boiler water has made it back around the loop, and air is purged. Shut the boiler drain and open all loops again.

The individual zones are all connected to the main loop, so watch the pressure gauge to make sure pressure comes back up to at least 12-15 psi, even 20psi is ok. The pressure reduction valve (mushroom) with the small handle on top should automatically fill until pressure is correct. If it doesn't, replace it. Also check your automatic air vents. The air isn't being bled out by them like it should. Unscrew the tiny lids on the top of them some and GENTLY push down on the needle valve on the top. It will squirt some water and possibly air. If they were just clogged, this should help, if they are defective, rebuild or replace them.