Circulation direction in radiator system

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In my boiler fed, household hot water radiator system, is there a way I can determine the direction of circulation? I need to cut, cap and isolate a room to find a leak.
Thanks.
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There is usually a flow direction arrow on a pump. Also the inlet on a cast iron boiler will be higher (further from the burner) than the outlet. The newer low mass boilers undoubtedly have inlet/outlet labels somewhere.

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Look at the pipes/tubing leaving the boiler. There are probably a couple of valves in the system that will have an arrow on them showing flow. Then just follow the pipes.
I don't mean this to be nasty, but if you don't know how to find the flow direction, are you qualified to cut into the system?
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wrote:

I'm wondering why the flow direction even matters for his purposes. In order to isolate the area from the rest of the system, he needs to cut and cap both the supply and return pipes anyway... so why does it make any difference which is which?
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Doug Miller (alphageek at milmac dot com)
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On Jun 13, 10:22 am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

I need to install the snifter valve in the correct section. That is to say into the suspect room loop, not the still connected to the furnace loop.-
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Probably not but I can drain the system, I'm good at sweating copper and I'm fairly well mechanically inclined. It'll be a learning experience and money is tight. I need to learn not to be afraid of the system anyway for future problems. I have already located the two pipes I want to cut and now that you mention it, I believe the air purge valve has a direction arrow cast onto it. I feel fairly confident (famous last words). The plan is to install a snifter valve and pump the suspect loop with about 10 pounds of air.
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coustanis wrote:

Hey, thanks for teaching me a new term, "snifter valve". The one time I needed something like that I carved the brass part out of a tire rim valve and sweated it into a hole drilled through a brass pipe plug. <G>
Good luck with your project, it sounds like you'll be able to handle it, and I don't see any major dangers to life and limb from what you plan on doing.
"You can only succeed as far as you dare to fail."
Jeff
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Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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I just learned the term yesterday when I was explaining to the guy at the plumbing supply place what I wanted to do. The valve cost 1.49, and is threaded. That, the other three caps and a sweat-on-able(?) fitting for the valve to thread into cost all of 6 dollars. Cheaper than a plumber. Thanks for the good luck wish. I started last night and found that I had marked a wrong pipe. It's hard to trace those things sometimes. In and out of walls, through floors. I was really pissed off and cursing up a storm about not finding the proper pipe when my 5 year old points and says 'you mean that pipe right there?' It was the right pipe. My 5 year old is smarter than me. Now that everything is located it should be a quick job to cut and cap.
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It is unclear to me from this thread whether you realize that you must isolate both the feed and return lines to isolate a part of the system. Otherwise your pressure will still pressurize the entire system. Your reference to "a pipe" rather than "those two pipes" made me wonder.
Don Young
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I cut the pipe as close to where it enters the suspect room as I could and capped both open ends. Then I cut the pipe again as close as I could to where it exits the suspect room and capped only the exposed end that returns to the furnace. I then installed a special cap that I made with the snifter valve in the last exposed end (the one that is exiting the suspect room). I then refilled / repressured the now sealed furnace loop with water to 12 psi and verified no leaks. I then used my air compressor to pressurise the now sealed loop to the suspect room (via the snifter valve) to about 15 psi. Now I can see if the boiler pressure holds (it did overnight) and I can see if the air pressure in the suspect room holds. I haven't rechecked that yet but I strongly feel that it won't. I have thought all along that the leak is where the pipe is laid in the concrete pad of the suspect room. If the air pressure zeros out then I was right. If it holds then I was wrong and the boiler pressure would drop. There is definately a leak somewhere. Just trying to pinpoint it's location.
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What makes you think there is a leak? Do you see water?
Copper in concrete over many years can corrode and leak. Some older homes with copper radiant heat had problems and the solution was to change over to baseboard rather than tear up the slab.
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It is baseboard.
The reason I think there's a leak is because the boiler pressure drops to almost zero every couple of days and I can hear the water gurgling and flowing in the pipes as if the level was low. It didn't used to do either of those things and it suddenly started to do so one day. I see no water. That's why I have thought all along it's in the concrete pad. Knowing that pipe in concrete will corrode combined with the fact that except for the concrete pad, the piping in the house is largely exposed visually. Where it's not visually exposed it's in walls and such. I see no water anywhere. No puddles on the floor, no wet walls and no water dripping from ceilings. No water to be seen anywhere. Deductive reasoning (however faulty mine may be) dictates that it has to be in the pad and I guess it's flowing down and going somewhere as opposed to coming up onto the floor. I have been using my plumber as a sounding board and he seems to agree with my thoughts. I asked him if it could be a steam leak and he said no. Bless his heart for talking to me instead if insisting that he do it for a lot of money.
Anyway, the deed is done. I have isolated and pressurized the room in question so either it will lose pressure or the boiler will. I'll find out tonight when I get home. I'll keep you all posted. Isn't home ownership fun?
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If you don't find a leak, get back to us. There are other reasons you can hear the gurgling sounds, such as faulty expansion tanks, etc. There was a lengthy thread on this just last week. BTW, do you keep the feed valve open to the system? If no, did you before you had the problem?
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The expansion tank is brand new. I keep the feed valve closed and have always done so. I will get back to you. I need to let another day or two go by to allow the pressure to drop if it's going to.
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Read this posted by hvacmedic a few days ago. It is part of a thread from your original ost.

In retrospect, I think you said that you only had problems when the valve was closed. In that case, what I went over above is why you had problems before, i.e. with the valve closed. The valve is supposed to be open, so you didn't do anything special to your system, you only set it back the way it was supposed to be. Pardon the oversight.
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Ok. You lost me on all that. Let me read it a few times and think.
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I condensed it for you. It is very possible you do not have a leak. Try running the heat (if you live in a cool enough place) for a couple of days and leave the feed water valve open.
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Can I run the circulator pump with a loop capped off? Other rooms loops are still intact, so probably. Also, I believe I need to make sure the expansion tank pressure is about equal to the boiler pressure. That shouldn't be a problem, I guess. Just release or pump in air to about 12 pounds. No one has mentioned this possible scenario to me. Have been getting told it is a leak. If I leave the feed valve open and there is a leak, won't it just keep feeding in water and never allow the pressure to drop. That is why I was told to keep it closed. I also wouldn't know how far to open the valve (slider lever thingie). I tried that once a few weeks ago - opened it just a crack and the pressure was headed merrily up to the high 20's or low 30's. I shut it back off so the safety valve wouldn't blow. I may be getting in over my head at this point but I'd like to keep trying. If you keep talking, I'll keep listening.
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So you're telling me that air air in the expansion tank will diffuse into the water? I thought it was contained in a rubber bladder. I couldn't measure the amount of water I had to add every few days but I would estimate around a quart or so. Maybe more. Hard to tell. Not only do I feel like I've been barking up the wrong tree but I'm in the wrong damn forest.
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wrote in message

I do know that if I run the system with the feed closed, I do get some air in the system. I had a leak in the packing of hte feed valve and kept it closed and after time, air was gurgling. Replaced valve, left it open, a day or so later, noise was gone.
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