Why Vacuum: Understanding Fire Service
Vacuum Apparatus and Comparisons
with Conventional Apparatus
BY JASON ESTEP
There have been many
strides made in firefighting
technology in the past
At the beginning of the 20th century, firefighting equipment consisted of a
steam-powered piston pump pulled to the
scene of a fire by a team of horses. Once the
apparatus arrived on scene, some type of
water source had to be secured to effectively fight the fire. Modern day apparatus have
evolved into high-horsepower, high-volume
pumping machines that have tremendous
advantages over earlier apparatus. However,
one thing remains the same: Once arriving
on scene, a water source still has to be established to properly extinguish the fire.
Since the majority of the United States is
rural, many communities are not blessed with
water systems, and if they are, they are often
weak systems. Regardless of the reason for
a feeble water supply, the fire department is
still charged with the responsibility of properly controlling fires within its community. This has caused most fire departments in
rural America to depend on streams, ponds,
lakes, rivers, etc. to provide water for firefighting operations. The only problem is to
get it from the source to the fire. To do this,
tanker shuttle operations are set up. A tanker
shuttle consists of individual trucks, usually with large tanks, transporting water from
point A to point B.
The flow rate of a tanker shuttle depends
on two variables: dump time and fill time.
The Insurance Services Office (ISO) formula for travel time in a two-mile shuttle is a
constant 35 miles per hour. To increase flow
rates, departments began trying to lower the
fill and dump time. Lowering the dump rate
was easily accomplished by placing 10-inch
Newton gravity dumps on trucks. The problem is you cannot dump what you have not
1,250-gallon-per-minute (gpm) pumper must
be committed to fill a tanker. As a rule of
thumb, the fill site pumper will only be oper-
ating at 70 percent efficiency. Combine that
with the fact that most conventional tank-
ers have only one 2½-inch direct tank fill,
and you can see the difficulty in reducing fill
times. Now, examine the number of person-
nel needed to fill the conventional tankers.
You must have a fill site pump operator; at
least one person per tanker (in a large shut-
tle) to connect the hoses; one person tend-
ing to portable pumps/drafting operations; a
driver for each tanker; and, in a large shuttle,
more fill site pumpers to reduce wait time.
Next, let’s examine the setup time for a
fill site operation. A drafting operation has
to be set up, whether it is directly from a
water source or from a dump tank being supplied by portable pumps. If portables are
used, crews must take time to set them at
the water source, stretch the lines, and get
the dump tank set. Once the drafting operation is established, personnel must lay out
fill lines along with any adapters or appliances needed to fill each tanker in the shuttle. This all has to be done when the attack
crews are fighting the fire and needing the
water the most: at the beginning. There is no
doubt that after everything is set up, with
enough personnel and trucks to establish
an efficient shuttle, it is usually well into the
fire suppression effort. Most of the time our
tankers do not meet the needed fire f low of
the fire, but the fire burns down to the flow
rate provided by our tanker shuttle before it
A Different Type of Tanker
What if there was a tanker that could
cut the staffing required at the fill site by
more than half, fill itself without a pumper,
and offer a flow rate much better than that
of an ordinary tanker? Sounds impossible?
If a tanker like that was available, it would
revolutionize the fire service. This tanker does exist in the form of a vacuum tanker. It works using a very simple, yet efficient,
system that requires little maintenance and
is easy to operate. Vacuum was introduced
to the fire service market in the mid 1980s.
Although vacuum had been used for years in
the industrial field, it had never
been engineered for the fire ser-
vice. Many companies have
tried to use industrial type vac-
uum units in the fire service but
have been unsuccessful because
they have not made the neces-
sary changes to get the perfor-
mance and safety required by
the fire service. Innovative fire
departments have realized that
rapid water movement involves
more than dumping quickly. It
is a complete system with the
ability to rapidly load from the nearest water
source, safely transport it, and then quickly
evacuate the water from the tank.
As tested, a vacuum tanker can create
and maintain flow rates close to the 250 gpm
required by ISO by itself. It can self load at
approximately 1,000 gpm (usually more with
fill rates that can approach more than 1,300
gpm; 1,000 gpm is a safe “average” number
for vacuum tankers) and self unload at 1,250
1 A vacuum tanker can effectively obtain water at the
closest source without the need for a fill site pumper and
with minimal personnel. (Photo courtesy of Firovac.)
Vacuum Pumper FAQs
1. What is the dump rate of a vacuum tanker? The vacuum tanker will
dump at a consistent dump rate of 1,400 to 1,500 gpm. It starts dumping
at this rate and ends dumping at this flow rate, effectively emptying the
entire tank. This is why ISO recognizes the vacuum tanker as a “
zero-loss tanker.” ISO penalizes a conventional tanker 10 percent of its tank
capacity because of inefficient dumping, meaning that the vacuum
tanker is delivering 10 percent more water each trip. Some gravity dump
tankers can begin to dump at more than 2,500 gpm, but the flow rate
drops the entire time the dump valve is open. If you average the flow rate
of a gravity dump tanker, it averages in the 1,250- to 1,500-gpm range.
2. Can it fill from a hydrant? Yes. With the flip of a switch (which opens
the internal tank vent), you become just like any other tanker on the
road, with the ability to fill from a hydrant or fill site pumper, although
there may be some loss of efficiency as compared to vacuum operations.
3. I require a fire pump on my tankers. Can I get it with a fire pump?
Yes. Many vacuum tankers have been built with any size or pump
configuration available, including pump and roll. This makes for a very
versatile apparatus. I like to say that you can make a vacuum tanker
perform the function of any conventional apparatus, but a conventional
apparatus can never perform like a vacuum tanker.
4. Is there a maximum fill rate/pressure? There is really no restriction of
pressure or fill rate. We have filled our vacuum tankers from hydrants
that operate in excess of 230 psi. The tank is properly vented to handle
this. This is in contrast to a conventional polypropylene tank, which is
restricted to 100 psi or 1,000 gpm. Failure to abide by this can and will
void the polypropylene tank warranty.
5. Is the vacuum tanker limited to filling in deep holes of water?
Nothing could be further from the truth. It actually excels in filling from
shallow water sources. This makes water sources available that were
previously unusable. Unlike a conventional fire pump, the vacuum
tanker will not lose prime if it sucks air. Having the ability to use the
closest water source can make the difference between success and
failure on the rural fireground.
6. Can the vacuum tanker nurse a pumper? While I am not a fan of nurse
tanker operations, the capability does exist to nurse a pumper from the
vacuum system, which can provide approximately 15 psi of pressure to
nurse the intake of a pumper. This works well in supplying a pumper
in low-flow situations such as vehicle fires, nuisance fires, and some
wildland operations. The disadvantage to this is that if the pumper
starts pumping hard, it may collapse the hose you are using to nurse.
A more effective method to nurse is to take a piece of hard suction
and connect from the vacuum tanker to the intake of the pumper,
eliminating the chance of sucking the hose together. This arrangement
can support fire flows approaching 1,500 gpm. I am a believer in setting
a dump tank, but this style can be used to support a high-volume blitz
attack while a hoselay is initiated from the hydrant.
7. Can a vacuum tanker be made into a Class A pumper? Yes. A number
of Class A pumper/vac tankers have been built.
8. What if the vacuum pump fails? The vacuum system has proven to be
very dependable, and the likelihood of a failure is very slim; but, like
any mechanical system, things happen. In the event of a failure, you
still have a tank on a truck, meaning you still have the same capability
of any conventional tanker on the road. You can fill from a pressurized
source (hydrant, fill site pumper).
9. How high can the vacuum tanker lift water? Just like a centrifugal fire
pump, this is dictated by the laws of physics. Thirty-foot vertical lifts
have been achieved, but this can vary with elevation. The advantage is
that the vacuum tanker will get the water every time. For a pumper to
access water from high vertical lifts, everything has to be nearly perfect.
In a horizontal suction hoselay, the vacuum tanker is only limited by the
hose it carries.
10.Does it meet NFPA? Properly constructed vacuum tankers meet or
exceed NFPA requirements for tankers.