I've read online how to shut down the system and purge the air from the
individual baseboard units in each room...but frankly I've got a lot of
those units......and when I last had my plumber in here he said I could just
open up one of the values on the return near the Boiler and drain the water
out...he said drain until you no longer hear the "spurts" of air coming out,
and its just water. Then turn the furnace back on and let it fill itself up
again....and rebuild its pressure.
Ok...its worked fine every time over the past few years...except for this
For some reason now I think its another zone, because draining some water
from my system resulted in a drop in waterpressure (temporarily) but no air
seemed to bleed out...this was from the return spigot I usually use.
I've got two other red knobs that are on the return line...a little less
convenient for me to reach to, but they're doable..I just have to be careful
not to totally scald myself.
As I understand it, the object is to:
1) Shut off the furnace
2) Let the water cool a few hours so I dont burn myself on any blistering
hot water (I'll wear gloves just in case).
3) Close the valve swich for that zone (located after the drain spigot on
the way to the main return line) so that any water coming out will
definately come out of the spigot and not continue on through the rest of
the return system, back into the furnace.
4) Open the spigot with either a drain hose or a bucket underneath and drain
out the water, or at least a majority of the water until one hears the
spurts of air disappear.
Now here's my question: If you drain out the water this way, don't you need
the furance ON to provide more water AS the air is being bled out? Or does
the automatic refill/leveling of the furnace happen independent of the
furnace actually being on or off (ie: turning the furnace "on" really just
means turning the heat and electrical relays for the zones on).
I'm kinda confused....and wouldn't mind paying to have my plumber come and
show me whats what, but I'd rather not waste his time if I dont have to.
Now my question is this: With the furnace off as I drain off this zone,
You have the right plan.
You turn off the boiler to get the pump to shut off and all the zone valves
to open. The water pressure for the purge comes from the compressed air in
the expansion tank. The lost water will slowly refill from the Pressure
Reducing Valve whether the boiler is on or off.
Ok, here's a followup question:
If I drain a bunch of water out of that pipe, and I then return the system
to operational and turn the furance back on, wont the pipe just fill up with
I would think I'd need to let that zone run with the furnace on (pump
running) to "Push out" the rest of the air....or again am I relying on the
pressure in the accumulator tank to handle that task..
Just a few thoughts of mine..... If you drain water out of a pipe, air has
to enter the pipe/system to allow water out. Otherwise the water will not
run out. So if that's the basis of your question.... why do that instead of
venting the air out of the pipe? That's what's usually done.
It sounds to me as if you have a fair amount of air in one zone and it isn't
being flushed out to be vented. That air is compressible and seems t obe
preventing pressure buildup in the system. These type things usually happen
when we short cut procedures. You/he didn't want to spend the time to vent
each vent, so for years it's been done this way, now it's time to pay up....
usually, there's only one way to do something right and it's specific to the
plumbing system with the problem.
Quality Water Associates
Gary Slusser's Bulletin Board www.qualitywaterassociates.com/phpBB2/>
I've got 4 zones on my furnace. Of the 4 zones, I can actually see 3
physical purge spigots,
with shut-off values just after them for isolating the "circuits" from the
pipe. All of them find their way to the main return pipe.
The furnace is a Crane and it's original, so figure early 60's....so far
the furnace has run just fine, no
leaks, no issues, and while I'm sure I could get better efficiency if I
replaced it, it seems to be
doing the job. I haven't had it serviced however...wasn't sure if anyone
even worked on
equipment this old anymore.
When we first moved into the home we saw the pressure spiking as high as
which I quickly learned was a bad, bad thing. The pressure-relief valve was
supposed to dump
at 30.....it must have been rusted shut.
Problem was determined to be a bad accumulator (pressure regulator tank).
That was replaced,
a new pressure relief valve and offshoot pipe was added, and a new
air-release value (the red-capped thing)
Now the pressure stays steady at around 12-14psi, never goes higher, and
only goes lower if I drain
hot water from the system (like when the pipes are doing the waterfall or
boiling-water sounds and I figure
there is air in there). It has stayed this way for 2 years. During the
summer I physically shut off the
furnace, the pressure dips down to about 8-10 psi......(perhaps this is my
evaporating from the air-release valve??).
Typical New England colonial, 3 stories...basement (where the boiler is),
first floor and 2nd floor. One zone in basement rec room, two zones on 1st
(one zone for each "side" of home), and one zone for upstairs bedrooms.
I have a big grey tank that I call, thanks to those engineering classes in
college, an Accumulator.
SOme call it a pressure regulator. That sits underneath the main "out" pipe
from the furnace, before it hits
the zone control valves. Above that grey accumulator is a pipe fitting that
is raised up, with a new air-relief
valve on top of it....its a little cylinder with a red cap on top that I now
have set to be very loose (the cap not the
The odd thing is that before, each year when I'd hear a little bit of
waterfall or gurgling coming from the
pipes, I could just hit one of the spigots....and the water would gush
out...blurting with air....the pressure
in the system would drop a bit, and I'd stop getting bursts of air...then it
would be fine for the rest of the year.
There is one "spigot" on the returns that is easy to access, so thats the
one I'd use. Its particular to one of the
But whats different *this* year is that when I use the same drain valve I
have in the past, I get solid water...no air "pops". Hence I think the air
may be more "congrugated" in one of
the other pipes in the system, ie: one of the other zones. The only thing
that *sucks* is that the spigots for those
pipes are difficult to access....well, without burning myself on the other
piping around them...I'll have to tread lightly.
For what its worth, I'd love to hear an answer to this....but I've decided
to call in the pros.
I'm having my Hot water heater replaced (its 16 years old) next week, and my
plumber is going to drain and purge the system for me,
and show me how to do the same thing myself if I need to again....I'll also
have him make sure the air-release valve is functioning.
Could it be shutting off the furnace during the summer months?? Should I
instead just drop the thermostats to below 50 instead of
turning off the system?
"The water pressure for the purge comes from the compressed air in
the expansion tank."
And your the professional, where's Hot when you need him.
The purge is done with constant high pressure (street main pressure),
in theory your making your loop a water line. Call a professional and
let him instruct you to the proper method for your system. Systems may
very slightly but the basics are the same.
Where is street main pressure going to come from? Unless you have a bypass,
all make up has to come through the PRV. Not enough flow through the PRV
to purge with. What happens is the push comes from the expansion tank and
the PRV refills the expansion tank.
Call a professional and
Where is street main pressure going to come from? Unless you have a
Street main pressure will come from a bypass or a fast fill such as
the B&G- FB-38. You really are a novice at this aren't you. You
actually offer a heating service to the public, amazing! Would/could
you actually give us some insight to your education in hydronics.
Dan's column in PM mag won't cut it.
The only reason I responded was due to the bogus info. your passing.
I never said I knew it all. You said street pressure will come from a
bypass or a fast fill PRV. That's all well and good if the house has a
bypass or a fast fill PRV. But it's not going to help much with the
majority of residential hot water heating systems that DON'T HAVE A BYPASS
OR A FAST FILL PRV. In those cases, the purge pressure WILL COME FROM THE
EXPANSION TANK, until the slow filling PRV refills the system.
Did you have anything else? I'm all ears waiting to learn something.
Obviously if the system is designed to be purged correctly it will
have a way of inducing street main pressure for a constant flow. If
not it should be corrected. You state the majority of residentual
systems don't have a bypass or fast fill. True but they are not
designed to be purged, only a series loop can be purged and it must
have a constant swift flow to remove and purge all trapped air. You
never asked if the fill valve had a fast fill lever or if a bypass was
present, you went right to this is how its done. There's a little more
to it then closing the purge valves and draining a bucket or two from
each zone at the valves. If he dosen't understand the principle behind
what he doing he shouldn't be attempting it and you shouldn't be
encouraging him especially with false information. If he's willing to
learn, teach him so he fully understands the principle behind what he
going to do before he dose it. Mark I'm sorry for jumping on you but
I've personally seen the outcome of makeshift work and it dangerous,
almost cost a homeowner his life and he was just a bystander while the
so called professional was at work. Poor guy caught the full force of
the relief valve discharge at 200 degrees as he turned the corner. Not
a pretty sight seeing the skin roll off his body.
OK. You make some good points. On a list like this people are constantly
asking for DIY advice and I agree that many times the best thing to tell
them is call a professional. Maybe this is one of those times. I
definitely have a problem with telling a DIYfer to touch the bypass valve.
After reading all the posts, it sounds like HeadRusch has a common diaphragm
type expansion tank attached underneath a "boiler scoop" (simple air
separator). The top of this boiler scoop will have an automatic air
eliminator attached to it. It sounds like all the air is trapped on the
higher floors. As the air is usually less dense than water, it will be
trapped wherever the piping turns to go down. That is the point to bleed the
air from. There is no need to drain water from the boiler, open bypass
valves, or cool off the boiler. Just turn up the room thermostat and find
the small vent at the end of the run of baseboard. The vent is usually a
manually operated device (small coin or screwdriver) but may be a variation
of an auto vent. Open the vent slightly and vent the air, using a small
container to catch any water. If you can avoid introducing fresh water into
the boiler system, eventually all the air will be gone, and you won't have
to do it again. I do agree that the water pressure should be higher, though.
Ideally there should be around 5 psi at the top floor. Pressure at the
boiler can be figured out by taking the difference in elevation from the
pressure gauge to the top radiator (in feet) and multiply by 0.434. Take
that number and add 5 psi. Set the pressure reducing valve to obtain desired
First the guy says his plumber, who has been working on this system, told
him how to purge a zone without opening a bypass or using a fast fill PRV,
but the guy wants to know if the water will be made up without the boiler
turned on. So I tell the guy that the PRV will refill the expansion tank
slowly whether or not the boiler is on. Then Kenny jumps me for telling the
guy he can purge without a fast-fill PRV or bypass like it was my idea.
Then Dean, who is smart enough not to weigh in until the dust settles, comes
in with a perfect post right on the money. LOL
That would be correct (re. my layout) Upon examining my system, it was
determined that my air
was probably becoming noticable because of my low system pressure. We
more water into the system, but the system pressure wouldn't rise above
We managed to get more water into the system, bringing the standing pressure
up to 18psi.
No more air bubbles. So far the system is holding at that pressure....it
ups to about
22psi max when its running full out, but otherwise its behaving like normal
no bubbles, no gurgles.
I'm just keeping an eye on the pressure......
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