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Dragon 10-20-2006 02:34 PM

Bleeding air - Hot Water Boiler
I have a Utica boiler that is approximately 10 years old and it is heating a tri-level house. The hydronic system consists of the boiler, 1 pump, expansion tank, Spirovent, and 2 zone valves. Those are the major components, ask if I left something out you need to know about.

The 2 different zones are as follows. The first delivers hot water to the basement floor slab. (copper line in concrete) The second zone feeds the upstairs levels. Level 1 is the dining room, kitchen and living room. level 2 is the three bedrooms and a bathroom. The hot water in the upper levels is delivered to base board units consisting of copper pipe with fins sticking out from them.

The pressure release valve was recently replaced and now I have air in the lines. The contractor I had come out to do this had to come back a second time as the system started pressurizing over 35psi and releasing water due to the air in the lines. On this second trip he attempted to remove air from the lines to fix the pressure problem. He was able to solve half the issue.

Now the system fluctuates nicely right around 12psi but it is only delivering heat to level 1, the upper level bedrooms are not getting any heat. Level 1 also gurgles and makes noises.

So neither of the upper levels has all of the air removed from them. I have Googled a number of webpages and many refer to bleeding valves. My system does not have these. The pipes come up out of the floor, pass through the base board unit, and then turn right back into the floor. There is no device on any of the units in any of the rooms or their adjacent closets that allows for removing air.

And the contractor, after not returning my phone calls for two days, now said I should try to bleed the thing myself as, Bla Bla Bla, he can’t/won’t be able to come out till next week. Not returning the calls was not a great customer service move. I have a pregnant wife and we slept in a cold bedroom for two nights. So before dropping another couple of hundred dollars getting a different contractor I figured I could at least give it a shot.

With a system set up like this I believe what I need to do is attach a hose to the drain valve, open it up and begin to let the water out of the system. Since it is automatically replaced by city water the air, after a long time, will hopefully be pushed out or at least moved to where the Spirovent can work on getting it out. Do I need to see if I can increase the rate at which the water enters the system to try to develop “more push”?

You suggestions, advice and comments are welcome.


#CARRIERMAN 10-20-2006 08:16 PM

Hi Dragon

Hope you are patient, this is going to take awhile. Start by shutting your boiler down. Turn thermostats up in all zones so water will circulate through all water lines. I am pretty sure you said this system had an air scoop. If it does there will be an air bleed on top of it. Now to the next step: Now that you have done the first step, Bleed some of the pressure off of the system by draining some of the water from the top of the boiler. If you have a horizontal expansion tank setting higher than the boiler drain the water from it instead of the pressure relief. Start shutting zones off starting from the bottom and working your way up, you will have to have two people for this process. Let pressure reducing valve keep system full, I have never had or seen a need to overpressure a system. One you think you have moved all the air out, start your boiler back up. Starting with the top floor start turning your thermostats back on. Yes there are alternatives to probably do this faster. But you will need to completely understand the system and its components to use them. This will probably be the safest for you and a very expensive heating system. Just remeber, do not overpressure system, take your time and let it move naturally.

Good luck, If this does not work to your satisfaction. I will give you some of the more difficult solutions.

#CARRIERMAN 10-20-2006 08:22 PM

Hi Dragon

I missed part of your letter. I missed the part about the baseboard heaters. Pull the fronts off of your baseboard heaters. Look on one end or the other, you will see a chrome or brass piece with a screw in the middle of it. Put a bowl under this fitting and turn the screw counter clockwise slowly. When a solid stream of water comes out, turn the screw back in. Repeat this process on all baseboard heaters. You will need to shut the pump and the boiler down for this. Sorry I missed this the first time. If these do have the air bleeds on them, disreguard my first response.

Good luck

Dragon 10-23-2006 08:49 AM

System working
I spent a good part of Sat. afternoon working on my boiler. By using the various zone shut off valves I was able to isolate the area that had the air in the lines and after quite some time of running water through it I was able to remove the air or at least the majority of it.

Now the lines on Level 1 do not gurgle or make noise and Level 2 is receiving heat like it is supposed to. The only noise in the system is from the noise the pipes make as they heat up when hot water circulates in them

It would have been alot easier if I would have had those bleeder valves on the base board units but whoever put in this system did not put those in. I also would not want to go through the mess of installing them after the fact either.

Final question for you:

Should the water input for the system, that is the city water coming in through the pressure reducing valve, be left in the open or closed position? What are the pros and cons of this?

I appreciated your previous posts as they made me feel a little more comfortable playing around with the system before calling the $$$ repairman to come do the same work.


#CARRIERMAN 10-23-2006 09:10 AM

Hi Dragon

The pressure reducing valve should be left on at all times during the heating cycle. This allows the system to refill with water as the air seperates out. On a new system its not unusual to take a couple of weeks to get the majority of the air out.

If you need anymore help, let me know.

Dragon 10-24-2006 03:39 PM

Still Leaking
Well, I thought I had it fixed.

I appear to have all the air out of the lines and I am getting heat in the house.

Now the problem is that when the boiler fires up to heat the pressure goes up and the pressure release valve starts doing its job by releasing water on the floor. PSI starts goes down to nothing when no heat is applied and goes up to between 20 and 30 right after finishing a heat cycle.

Maybe I have a faulty Expansion Tank? Not many other reasons I can think of as to why I should be getting this high pressure reading.


#CARRIERMAN 10-24-2006 04:09 PM

Hi Dragon

Most pressure reducing valves have a handle that you can move back and forth. Check your pressure reducing valve and make sure it is in the Auto position and not in the Fast fill. If it is in fast fill mode just push lever over to auto. If your pressure reducing valve does not have this, the tech that worked on it may have turned pressure adjusting screw in. If that is so, back the screw out all the way, bleed the pressure down by using the pressure relief. Slowly turn adjusting screw in until you reach about 12-13 lbs of pressure on gauge. That should solve your problem.

Let me know if you need anymore help.

Dragon 10-28-2006 10:24 AM

Finally Fixed, fingers crossed
I tried adjusting the pressure reducing valve for the incoming water but that did not work.

I spoke to another person who has experience with expansion tanks and he said I should check the little valve on the expansion tank they use to pressurize it. This is the same kind of valve found on a bicycle tire, a Schrader valve. (the expansion tank is the kind with the bladder in it)

My boiler is tucked in a small cubbyhole under the stairs so access can be challenging. I was able to reach back and depress the valve and LO and BEHOLD water came out. There should have been a hiss of air and not water. The water indicates that the bladder inside has failed and the expansion tank will no longer function.

Now, having found the problem, I was hoping the fix would be easy. My expansion tank has a shut off valve that seperates it from the rest of the system. It should have been a piece of cake to turn the valve to isolate the tank, unscrew the tank and then reattach a new tank. Right? Sounds simple. I wish.

The old tank had rusted solid to the line and the soft copper piping actually twisted as I applied torque to unscrew it. So I had to get my pipe cutter and cut the tank free. The tank of course is filled with water and probably weighs about 30 pounds. It is tucked back in this little cubbyhole so I had to wedge a cardboard box in there to hold the thing up as I cut it free. Then after cutting it free I had to manuver it clear of all the pipes to get it out. Easier said than done. Try bending over at the waist and extending your arms fully while holding and manuvering a now wet, heavy, slippery expansion tank. Gotta eat more Wheaties.

Then a trip to the hardware store was in order to get the necessary fittings and elbows to replace those that I had just cut off with the tank.

The assembly of the elbows went smoothly but I had to resodder the fitting to the rest of the pipes twice as after the first time the pipe was about 1/4 inch too far over and the threads on the new expansion tank would not line up to screw in with the limited space available.

So, for the last twelve hours there has been no release of water from the preseeure release valve. I'll continue to monitor it and keep my fingers crosssed. Thanks for all the assistance.


747 10-28-2006 11:21 AM

Wow your furnance is only 10 years old and you had to do all of that. Mine is `1963 But i did have a new expansion tank put on 2 years ago. The old one wasn't holding pressure. I think i need to charge the current one up alittle also. But i can't find tire guage. See a furnace should hold pressure when off. Mine goes down less then 12psi which is what is suppose to be in tank. But once furnace is on continually like now it will raise the pressure back up to 12 psi. So this is why i haven't unscrewed expansion tank to check and see if its still at 12 psi.

redline 10-28-2006 04:09 PM


Originally Posted by Dragon (Post 22085)
The tank of course is filled with water and probably weighs about 30 pounds.


You could have drilled a hole in the lower part of the tank to drain the water before removal. You may have air in the system after replacing the expansion tank. May have to bleed it.

What does the pressure gauge read?

#CARRIERMAN 10-30-2006 08:13 AM

Hi Dragon

Glad to see you are on the right path, All you should have to do is shut the iscolating valve and remove the expansion tank. As redline suggested before, you can drill a hole in it to relive pressure. If you choose this method however DO NOT USE ELECTRIC DRILL, the water will come up the drill bit and go into the motor. My suggestion would be to break the expansion tank loose an slowly let the pressure bleed down around the threads. The other thing to remember when replacing expansion tank is to get one for hot water. A well water one will not last. The most common one for 1/2" pipe size is a #15. Get ready though they are slightly pricy.

Good luck, let us know if we can help further

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