Nurse Tendering and Why Drop Tanks Are the Way to Go

Got Big Water has been posting some formerly published articles. One was from the "FireRescue" publication by Wayne Eder on 04/01/2011 entitled "Basic Rural Water Shuttle Ops".

Although it is an older article, it still holds up today. He addresses "The Nurse Tender" stating: Many progressive and well-trained fire departments still rely on the antiquated "Nurse tender" concept, in which a water tender pulls in and pumps directly to an engine company, providing a continuous supply of water until the tender runs dry and must go refill.

There's a basic formula for water shuttle that must be addressed to help us understand the weakness of the "nurse tender" concept.

Unload or dump time (UT) = Travel Time to Fill Site (TTF) + Fill Time (FT) + Return Time (RT) = Total Fill/Dump Cycle

Using this equation, with a fill site two miles away, and basing the travel time on a conservative 35 mph, the total time to shuttle on a 2,000-gallon tender would work out as follows:

UT (pumped off in 22 minutes) + TTF (6 minutes) + FT (5 minutes) + RT (6 minutes) = 39 minutes.

If the pumping engine is using a 500-gallon tank and flowing 100 GPM, it will be empty long before the "nurse tender" returns, thus allowing the fire to spread and placing the lives of both firefighters and victims in jeopardy. THIS IS AN EXTREMELY INEFFICIENT AND DANGEROUS PROCESS THAT CAN BE CORRECTED THROUGH THE USE OF PORTABLE TANKS." For example, with Firovac's portable tanks.

"Many firefighters avoid the use of portable tanks for a variety of reasons (weight, deployment, fear of drafting, etc.) but in the rural environment, the portable tank is your best friend. In the aforementioned scenario, we can improve operations dramatically by deploying a 2,000-gallon portable tank alongside the attack engine. Our new formula would look something like this:

UT (through the dump valve in 2 minutes) + TTF (6 minutes) + FT (4.5 minutes) + RT (6 minutes) = 18.5 minutes."

THAT IS BETTER THAN HALF THE ORIGINAL SCENARIO, PLUS the pumping engine then has a reserve of water, not just the 500-gallon in the tank on the unit, which may sustain flow until the tender returns. 

How many rural departments have fill sites within two minutes of a fire? Vacuum units have a greater chance of accessing nearby static water. Many non-vacuum units drive further distances to hydrants but we will not change that time in this calculation. 

A drop tank can usually be deployed proficiently in the same amount of time it takes to pull a hose and hook to the pumping engine.

This is a no-brainer. Why are we regressing to "antiquated" technology, just so everyone "fits in"? Why should we "fit into" a cumbersome system? Are we not there to put the fire out as quickly and efficiently as possible?

Not a lot of change is needed to accomplish this. 

Hello!I believe that I have found a couple of weaknesses in your argument:First, I need to say that in my region, ALL fire companies use portable tanks rather than nurse tenders, so I am in fact going against local policy in presenting these arguments.However: in paragraphs 6 and 7 above, your math assumes that there is going to be only ONE tanker coming to the scene, and  implies that that nurse tender has not done much good for the attack before disconnecting and spending 19 minutes going for water.  In reality, the 2,500 gallons available on the engine and the 'nurse' is going to provide a LOT of fire knockdown with a well-trained crew ("pumped off in 22 minutes" + "500 gallon booster tank @ 100 gal/min" equals 27 minutes of firefighting time).  With the far smaller crews that we are running with nowadays (at least in our region), a tanker crew of 1 or 2 people can be a tremendous and possibly DECISIVE asset to the first attack, AFTER they connect the 'nurse' to the engine.  Remember: this activity is occuring early in the attack, when it will do the most good.  Hopefully, the first arriving mutual aid tanker will arrive before that 27 minutes are up, drop their portable tank at the opposite end of the engine and fill it, and depart for their 19 minute refill.  When the nurse tanker is empty, the engine shifts to the filled portable tank while the nurse disconnects and joins the tanker shuttle.IN ADDITION: Paragraph 10 neglects to take into consideration that the nurse has ALSO provided the SAME amount of 'reserve water', plus the additional personnel for attack (early on, when it will do the most good) before departing for their 19 minute run for water.  All this, of course, assumes that you have no other tankers available to help you.Considering a different set of conditions makes your time argument against nurse tankers seem more valid:For your first attack, instead of flowing 100 GPM, you are probably going to be using a 1 3/4" hoseline flowing 175 GPM.  This reduces your attack time to 14 1/2 minutes, which, using a portable tank will STILL require pulling your people out of the structure to await the tanker's return in 19 minutes.But the additional crew from the nurse tanker might provide the resource to man another 1 3/4, 175 GPM line, giving you twice the knockdown in a transitional attack, plus satisfy the "2 in + 2 out" so you can go interior.  Early, when it will go the most good.  (You had better have done some real good with that 2,500 gallons of water, because you'll be done applying it after only 7 minutes!)I guess that it is all dependant on whether you have more tankers on the way (by policy in our region, we automatically have a minimum of 3 mutual aid tankers enroute for a structure fire), and whether your first arriving engine is adequately staffed.I look forward to reading the hornet's nest that I've stirred up!!---Bradley Fisk

Thank you for your comments, Mr. Fisk.  They are very perceptive and have several good points which I would like to respond to in different sections.  In Wayne Eder's article entitled "Basic Rural Water Shuttle Ops", which we referenced earlier, presented a true picture of "The Nurse Tender".

Section 1.  Why are we applying water at only 100 gal/min when we have 1,000-1,500 GPM pumpers?  Is it because we are not sure when another tanker will come or is it that we have been taught for years  that:  "A portion of the training of rural fire departments is taken up with engraving on the mind of the membership the need for the conservation of the meager water supply that is available in many areas." (Source NFPA 1231.1 publication of yesteryear).

After all we NEVER want to run out of water.  We often think we are applying more water than we really are.  We think we are applying it at the pumper's capacity but we cannot supply the water to meet the pumpers capacity and frankly, you are correct, not much more than 100 GPM.  So we have to ask ourselves, are we just prolonging the fire.  Larry Davis use to say "There are 2 times when you can extinguish a fire with a tea cup, when it first starts and when it has a final ember."  With todays construction materials a 100 GPM application is not acceptable.  

What can we do to improve?

Section 2.  I agree with your statement "in paragraph 6 & 7 above, (in the article) the math does appear that there is only ONE tanker coming to the scene thereby showing that the nurse tender has not done much good for the attack before disconnecting and spending 19 minutes going for water."  I think that is one of the points of the article.  How much knock down can we do at 100gpm application?  We apparently adjust our flow rate to the water we have, not to the fire suppression requirement. 

There are departments who do not "shift to the filled portable tank" but continue with the nurse scenario hoping another tanker will come before the initial nurse tanker returns. Even if another tanker comes with more water, when it leaves there is no water reserve for the engine as you pointed out.

IF the department would shift to drop tanks, the water supply would definately improve as you have shown in the remainder of your response and the article shows in the #2 scenario.

Section 3.

One more positive step to supplying water is with vacuum apparatus.  Not only does it discharge water into portable tanks completely at 1500-2000 GPM, it self loads at 1000-1500 GPM depending on water source.  Because it does not need to prime, it can load from almost any static water source (see pictures on this web site).  Therefore, finding a closer water source could change the calculations tremendously.

Example: Van, West Virginia supplied mutual aid to a neighboring department.  Non-vacuum units were driving 4-5 miles to a hydrant.  Knowing West Virginia's terrain, Chief Howell asked for access to the river.  Although he was told he couldn/t get water from there (because no one else could) Van used approximately 60feet of hose to the river with 20 feet of vertical lift and supplied water from approximately 1,000 feet away. An equation would look something like this: UT (1 minute) + TTF (2 minutes) + FT (2 minutes) = RT (2 minutes)= 7 minutes. This is BETTER than half the time of using a drop tank instead of nursing (second scenario in article 18.5 minutes) and 5.5 times BETTER than nursing only (1st scenario in article 39 minutes).  They alone delivered 140,000 gallons to the fire.