Hot Water Rad Bleed screws

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Old 09-21-12, 07:54 AM
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Hot Water Rad Bleed screws

So, going to be replacing about a dozen bleed screws this evening and firing up the boiler for the heating season.
Going into this, I have a couple quick questions.
The bleed valves I'm going with are pretty much the same as what I have currently and look like similar to this;
[ATTACH=CONFIG]3600[/ATTACH]

First, installing the new screws, what should I use on the threads of the new valves (teflon tape, some type of adheasive, nothing)?
There is definately no teflon tape on the current valves.

My second question...
I have a valve like the one pictured below on my third floor (and in two other locations on the main floor loop). The one on the third floor is a pain as it has to be bleed regularly if the circulation pump is not moving water to it regularly. Should I replace it with a valve similar to the ones I am installing else where?
 
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Old 09-21-12, 03:30 PM
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I wouldn't use tape on those. I would dab some Rectorseal #5 or Hercules MegaLock on the threads and screw 'em in. Don't over muscle them, they only need to be tight enough to not leak. Watch for leaks in the hours/days after installation and just snug them a bit until they stop leaking. The fine pitch thread is much easier to seal than the larger sizes.

The one on the third floor is a pain as it has to be bleed regularly if the circulation pump is not moving water to it regularly
I would absolutely lose the one on the third floor, and replace it with the manual one.

The thing about those float type valves is that if the pressure on the third floor ever goes BELOW atmospheric (and it well could!) then the durn thing will end up sucking air INTO the system! This might actually be why you have trouble with it!

Since you have a 3 story home, you need to run your system at HIGHER than a 12 PSI COLD fill. You should probably maintain it at 17 PSI when it's stone cold. This to insure that you always have a few PSI of positive pressure at the top of the system.

If you are curious about this, rig up a pressure gauge that you can install on the 3rd floor... you will find that the pressure could well be as much as 14-15 PSI LESS than what you read at the boiler. Then to make matters worse, if your pump is not 'pumping away' from the connection point of the expansion tank, every time that pump runs the pressure up top will go even LOWER!

If the ones on the loop downstairs are actually positioned such that air can collect in the pipe underneath them you could keep those. It won't hurt anything... BUT, if they are just sitting on a TEE fitting somewhere, and air never collects under them, they won't do a damn thing for ya.
 
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Old 09-24-12, 07:02 AM
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Replaced all the bleed valves with the broken heads, and the two of the three auto bleed valves.
It's amazing with a normal valve, it was really easy to get water up to the third floor rad. No more running up stairs, bleed, down stairs, add pressure, up stairs bleed... until I get water up there. Installed the valves, set the pressure to 20PSI and had all the air out of the third floor rad in one shot.

The second autobleeder I replaced was one I found this summer while inspecting the pipe work of the main floor loop. Was on an elbow on the main 1 1/4" pipe (not sure why). What a piece of nastiness this was.
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I have one more leak to fix (diverter tee, above the oil tank ) and I'll be leak free and good to go for the heating season.
 
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Old 09-24-12, 09:54 AM
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That one has been weeping for a LONG time!

Sometimes installers put the auto vents in at the end of long runs to aid filling and purging the system. They are useful for that purpose because they will let the air out as the pipe fills. Then, the cap would generally be closed until the next time they are needed... maybe that's what they were thinking?

I find that a good old 1/4 turn boiler drain works fine for this. I don't mind hooking up a hose to purge air.

Was that one mounted in a bushing in the elbow?
 
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Old 09-24-12, 10:27 AM
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This valve was mounted at the top of the elbow, which was very close to the joices, so I couldn't see what was above. The stem was a seporate piece and I had removed the valve by itself first, then the stem as it was a male fitting and I couldn't attach a bleed valve to it.
I know from talking to a few of the local service people (plummer, boiler guy, etc) that the previous owners did no preventative maintenance, so going around checked all the pipework for any issues was definitly not done by them.

The other autobleed valve I removed from the third floor was was visually in good shape. Not a spec of corrosion on it.
 
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