We have two freeze prone areas at work. They have a glycol system. The
pipes are filled with an anti-freeze solution and there is a reservoir tank
attached to it also in the last heated section. This was recommended by
both the sprinkler company and the insurance carrier.
The dry systems I'm familiar with had compressed air dryers for the
compressors to keep moisture at a minimum. I've repaired many a
compressor and air dryer system. The dry air was to prevent the exact
problems you mentioned. An engineer I was working with on the first
indoor cooling tower type setup in The Southeast, bumped a sprinkler
head with his hardhat and lucky for us it simply leaked so I tend to
believe the things are quite tough as far as resisting water hammer.
Around here, all new dry fire suppression systems must be tested for a
minimum delay from when the sprinkler head is tripped to when the water
starts spraying at the furthest head. This testing guarantees the system
will be wet inside. Blow the lines all you want but you will never get
all of the moisture out.
I suppose I should have written that the air dryers minimize the
introduction of more moisture from the compressed air source. I'm
curious as to how often the time to spray water has to be tested?
Is it a one time certification or is it an annual test? I know the
guys from the fire protection company don't want water pooling in
the unheated warehouse sprinkler systems so I don't what their
procedures are but I've taken automotive antifreeze and blown it
through pneumatic systems that were freezing up in cold weather.
If it was extremely critical, I'm sure they could blow denatured
alcohol through the system to get rid of residual water like I've
done on some pneumatic systems. I'll have to ask one of the guys
about it. I guess a fire would melt an ice plug? :-)
+1 to the fire melting the ice plug...
Although you would want to take every effort to prevent the ice
plug from forming as ice is pretty strong and can do interesting
things in pipes with the sprinkler heads installed facing downwards...
So it is more of a maintenance issue for preventing the heads
from blowing out and causing a nuisance discharge...
I could have sworn I've seen the sprinkler heads pointing up in a lot of
warehouses and industrial buildings. It could be for protecting them
from the goofy forklift driver of for making sure no residual water
collects in them and freezes. Once again, I'll have to ask one of the
guys from the Fire Protection company. It makes sense to do that in an
unheated building and I have seen different designs for the little metal
umbrella so there is probably one designed just for the upturned head.
The different designs of the "little metal umbrella" on the sprinkler
is to control the pattern of the water discharge from the head...
The different shapes create different patterns of spray from the head
(like the different heads for a pressure washer) as sprinklers
in different positions need to spray the water in different
Overhead sprinklers versus sidewall mounted, facing downwards
versus facing upwards from the piping...
Just once when the system is installed. After that it just has to be
serviced by a licensed fire protection co.
In the 17 years I lived there both systems tripped many times due to
malfunctions, accidental contact, vandalism, and car fires. Keeping the
pipes dry would have been a hell of a challenge.
After a watching the fire prevention company a few times. I could pretty
much have the system drained and compressor back up and running.
All they had left to do was blow out the low points one final time, shut
the main valve from the city water, drain the diaphragm check valve and
pressurize it from the sprinkler side, open the valve to the city water,
and sign off on it.
One time the malfunction was caused by a flaw in a seam of a pipe. The
pin hole got progressively bigger until the compressor could not keep
up. The system tripped (naturally on the weekend). By the time the fire
prevention guys got there on the Monday the small hole was about a
centimetre in diameter and the water was gushing out.
Darn, defective pipe. I saw a lot of that 20 years ago when I was
working for a big construction corp. when the black pipe came from third
world countries because they had the best price. There were all sorts of
pinholes and casting flaws in the pipe and fittings. I have to wonder
how long that stuff lasted.
+1 to what Nate said...
The expenses involved in all the additional sensors as well as the
special valves that each "dry zone" needs as well as the dedicated
air compressor for each zone required and emergency power to feed
it are enough of a barrier to reserve the use of "dry sprinkler"
to sections of a building where environmental concerns like freezing
temperatures are a factor in the fire protection system design like
loading dock areas, parking areas and entry ways and stairwells
which are unheated...
Get you facts straight! Dry pipe sprinklers are only used were there
is a danger of freezing. They are more expensive to maintain because
the condensate traps have to be drained monthly. The compressor for
the piping air adds cost and the differential dry pipe valve is much
more expensive than the Alarm Check Valves used on wet pipe systems.
Preaction only systems are only found were the damage from water might
well exceed the damage from a fire. Examples include museums,
historic library collections, fur storage, paper supply storage, and
similar occupancies. If you are thinking of a combination preaction
dry pipe system those are extremely rare and are found only in areas
exposed to freezing that are so large that an ordinary dry pipe system
would take too long to deliver water to the fire.
Typically the sprinkler risers are in the stairwells, with the floor
control valves on each landing. HOWEVER - if you are not a firefighter,
fire marshal, or sprinkler contractor, you probably don't want to touch
those valves, unless you like having legal problems. The valve controls
all the sprinkler for the whole floor, therefore if the fire is out in
your apartment but not in your neighbor's, and you cut the water off,
well, you get the idea.
I too share your concern on a visceral level about having all that
pressurized water in pipes above all my valuables, but honestly, the
sprinkler system is probably better maintained than the domestic water
supply. So long as you don't bust a sprinkler head (it happens,
especially with non-concealed types) you don't have a lot to worry about.
replace "roosters" with "cox" to reply.
The code in our state (maybe nation?) is that the sprinkler heads have to be
changed every 50 years.
They can go off accidently, but it is very rare. I've seen sprinkler pipes
banged by errant fork lift drivers and nothing happened. Except one time,
many years ago. To guys were done for the day and were racing back to the
charging station. They had the stand up type of lift and were playing
Chariot race, like Ben Hur. One went under a mezzanine with his fork partly
raised and he took out a 3/4" pipe. Lots of water in the storeroom that
At our business, they put in a new system in parts that had no sprinkler and
changed out some 50 year old heads. Never had one go off. The system is
tested twice a year.
Maybe if you bang the pipes, but if you hit the head there's a good
I've seen it happen several times, once in a hotel room where somebody
hung a clothes hanger on the head. (Doh!)
That little glass piece is fragile - it handles a good compressive
load but any sideways pressure will trip it, and an impressive amount
of water will come out.
What you are discussing in the stairwells is NOT the sprinkler riser
pipe but merely the fire hose standpipe riser which is an entirely
separate feed down the the fire pump room in the building (and in
some buildings the riser pipes are dry and require a fire pumper
truck to hook up at the external connection point after the engine
has established a water supply from a fire hydrant to feed water
into them) to allow the fire crews to obtain water to fight fires on
the upper levels without having to drag hoses in from the ground
Typical fire hose standpipe risers are 4" to 6" in size... The main
sprinkler piping in a building is generally 8" (small building) or
better with main supply pipes serving large sections of the building
being at least 12"...
That is a poor design -- that means that when serious sprinkler work
needs to be done (like replacing a floor control valve or the like)
whole building (including the standpipe risers) needs to be shut down
and drained... Leaving the entire structure with no fire water
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