Next week I start on the basement remodel project after putting it off for 8 months. Step 1 is to cut the pipe and remove the baseboard radiators down there so they’re out of the way while framing, I’ll put them back when the framing is done in their new positions. So that means opening up the hot water circulating system, which is a mess I haven’t made before. Slightly complicating things is that the basement plumbing leg does not have its own zone control valve, it’s just piped straight into the manifold. Whenever one of the other zones turns on, the basement also receives heat. I plan to install a zone valve on the basement leg (future kid’s bedroom) as part of this project. So when I cut the pipes in the basement, most of the water in the manifold will drain. So I plan to cap the pipes in the basement (no heat there for the winter, it used to get cold around here but not so much anymore), valve off that leg, and then I have to get the air out of the rest of the plumbing. This seems to be straightforward (I’ve thought that about other projects): attach a garden hose to the boiler drain, turn on the input water, and open the zone valves one at a time and flush water through until bubbles stop coming out. So in order to get out a small amount of air I will completely replace all the water in the system. Any hints on things to look out for here? Approaches I haven’t thought of? I’ve heard that when new water is heated up it will evolve some gasses that you want to get rid of, how it that done? Your help is much appreciated.
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Can't help you with your question, but want to point out the importance of maintaining the neccessay air supply to your boiler to support combustion - you can't just enclose it without allowing for sufficient air to get to it.
Some hot water heating systems have an automatic makeup water supply and an automatic vent valve to let gasses out, so venting would be automatic. They also usually have a head tank to ensure positive suction head on the circulating pumps- a small tank that you charge with air to maintian system pressure, or a tank high in the system. It may be less painful to pay a heating contractor to inspect the system and advise you how to do the work. If it costs an hour 's worth of their time to do it easily and correctly, it would be worth it.
i'm not sure what the point of the garden hose is. there must be an air vent on the top of the boiler somewhere.
so, here's what you do. do your plumbing stuff, and valve off the stub ends. try not to lose any more water than absolutely necessary (yea, right). open the valve that lets the makeup water into the system , and fill the system. it will now be pressurized to whatever your water supply pressure is (city water, or well/pump??). the air vent on the top will let accumulated air and noncondensible gases escape. typically, this will have a schraeder valve on it (like a tire valve); you can speed the process by pressing on the little valve stem, just like letting the air out of a tire. at some point, you will get some water bubbling out of it; then it is time to stop. if a subtantial amoutn of water was added, i would suggest running the circulating pump, and repeating the air release vavle process. this should help get some of the air out of the system in general. over time, the air will come out by virtue of the air release valve.
also, this would be a good time to make sure your expansion tank is drained; they tend to fill up with water over time.
Thanks for the suggestions. I think I will try to find a plumber who can spare a little time to take a look, which will be a challenge around here. There're a number of plumbing schematics in the boiler installation manual, and what I have doesn't really look like any of them. Better safe than sorry in this case.