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Tender Size vs. Drop Tank Size
Hi Folks - looking for some opinions out there on the size of the drop tanks used for tenders (tankers) and the amount of gallons that they carry.
Our dept. currently has two - 3500 gallon tankers and each tender is equipped with a 2000 gallon drop tank. We've had some "lively" discussions regarding purchasing drop tanks that equal the amount that is held in the tender.
The thought is that the tenders can pull on scene deploy their drop tanks unload completely and head out to reload. Which at times depending on where we are at in our area could take 15 to 25 minutes. The departments that we typically utilize for mutual aid run about the same size tenders but also have smaller drop tanks.
Opinions ? Big tenders - small drop tanks (easier to move) vs. Big tenders with large drop tanks ?
Replies to This Discussion
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Permalink Reply by Paul Spencer on
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In order to answer the question one needs to know what the Departments priorities are. There are clear reasons to choose one over the other, but they are based on what the end goal is. If the highest gpm water delivery was the priority then keeping the tender moving is critical. The volume of water delivered divided by the total circuit time equals the gpm provided by the vehicle. If the vehicle is sitting around waiting then the circuit time is increasing and delivered gpm is falling.
If on the other hand there isn’t enough room on the average fire ground or enough personnel to deploy a larger heavier drop tank then your tender shuttle turns into a nurse tending operation and the circuit time is very high. Some departments carry multiple smaller tanks and deploy them as necessary and connect them together in any number of ways.
I personally think that the tender needs to be operational with the initial attack personnel that are responding with the alarm assignment. Two people should be able to set up the drop tank and drop the first load of water before the attack engine runs out of water. If you are looking at a new bigger tank then try setting one up a couple of times before you buy it.
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Permalink Reply by Eric Gregory on
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I guess the biggest question is, does your current setup meet your needs? Can you set it up with the manpower you have on scene without completely stopping other operations to draw manpower? Do you run out of water on a regular basis?
What about utilizing both of the drop tanks you already have with a connector between them. You can rig up something that connects them drain to drain line and have 4000 gallons worth of tank space. The downside of this option is if your ground isn't 100 percent level then one of your tanks now has the drain up slope and we all know how much that can suck when it comes time to break it down.
The other option would be to look into building or buying a jet siphon and a pvc horse shoe to transfer water between the two tanks. The end result is the some 4000 gallons of on the ground water storage on scene.
You can even just use a PVC horseshoe without the jet siphon fill it with water, submerge one end in each tank and the water levels should equalize between the two.
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Permalink Reply by Don Catenacci on
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I don't understand the concept of not having enough drop tank capacity with the first tender to allow it to dump it's first load entirely. Speed is made up by how rapidly we can load and dump the water in the tank.
The only other way to get the capacity is to have multiple smaller tanks.
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Permalink Reply by Oldman on
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I personally feel that the dump tank matching the capacity of the tanker/tender is the way to go, but it might depend on a number of factors.
How often do you train on deploying dump tanks? How fast are you able to have them set up and have water flowing? And as has already been asked, do you run out of water before a truck returns?
My department has a 4000 gal tanker (ok, tender if you must) with a 4000 gal dump tank. We do timed trials several times a year with 1 engine with a 4 man crew, and the tanker with a driver only. From arrival of the apparatus, deployment of the tank, to the tanker leaving for another load, we are consistent at about 4 minutes. 2 men deploy the tank. As soon as the tank is open, the tanker/tender starts dumping, while the hard suction connection is made and pump primed and flowing water.
However, we are in an area which precludes us using dump tanks at most of our fires, so we nurse from the 4000 gal, and have smaller more maneuverable tankers fill the big one. Sort of a rolling dump tank. But we know, when we can use the dump tank, we can get them set up fast and with minimum manpower. What works for us, however, may not work for everyone else.
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Permalink Reply by AFD1424 on
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We rely on tanker shuttles for everything in our area no hydrants. In the department I was previously in we ran 4 - 2200 gallon tenders w/2000 gallon drop tanks. Jet syphoned to tie them all togather and it worked well.
With this department our issue is manpower. We have about 15 active guys on our dept. The tenders have cable assist winch for loading and unloading and the 3500 gallon tanks weight approx. 160 lbs. Two people can easliy move them, one person can do it if need be. The concern is when the second tanker will arrive from either our dept or one of our mutual aid depts. We may have a day when there is only one tender for the first 10 mins. I do not think we have ever been stuck without water for a considerable amount of time but just looking at things more efficiant.
We train on water movement a couple of times a year and are getting our JRFF's trained at being water bosses. To help us.
I'm personally for the larger tanks, the thought of dropping a larger tank, completely emptying the tender and having it on its way to refill in less than 5 to 7 minutes to me is ideal. I'm afraid of the bottle neck that creates while waiting to empty. To me it is just not running efficiant with the equipment that we have been given.
Thanks for everyones input thus far...
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Permalink Reply by Russ Marks on
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If size and personal is an issue, consider Tender 1 drop the tank and fill, nd nurse the leftover 1500 gal, Tender 2 drop and fill and transfer remaining to Tender 1 to nurse, Tender 2 hit the road, when the tanks allow, Tender 1 dump and hit the road. How often do you need more than 7000 gals. the majority of our fires are controled with the first alarm 3 engines and 2 tenders, rarley is a refill needed.
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Then you don't fight barn fires.
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Nope we don't. sometimes we do have the 5000 sq ft exec home with 3 car garage and 100 acres of vegitation around it. But for the avge home of 2000 sq ft we start with big flows to get knock down with first water on scene. Our biggest challege is June thru Nov and deal with large veg fires and for that you must stay mobile.
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Permalink Reply by Mike Gemberling on
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So many different situations and therefor so many methods. We were just on a small grass/light fuel fire in very rough terrain with nowhere to drop a tank. We rolled our 3500 pumper tanker and wedged it on the side of main road (gravel single lane). Then rolled our 1500 gallon tenders to nurse it one after the other. We have two. One of our main engines was at the lake landing a mile away filling the tenders. Our type 4 and type 6 engines then could fill on the main road off the tanker and go back to the fire quickly. There was no way to get anything bigger than our type 4 up there. Worked great and never ran out of water. One of the USFS engine bosses commented on how smooth and well we supply LOTS of water.
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We have a few barns left in our territory, but our biggest concern areas for protection are a school, church and two large gas stations. We do not have any hydrants. If any of those would start on fire and we needed to bring in a local ladder we most likely would not be able to keep up the needed water supply. Our tenders are vacuum tenders, so it fills quickly once all of the pieces are in place. Thanks for all of your comments....
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Permalink Reply by Ben Waller on
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After reading all of the replies to this point, there is a way to address this that I have not seen posted here.
However, before I post my solution, I want to discuss a couple of the trade-offs inherent in mobile water supply. As Paul Spencer says, one factor is keeping the tankers/tenders moving. That means the most efficient use of the tankers/tenders is to be able to dump the entire capacity of the tank into a dump tank without having to wait around at the scene.
The trade-off is that if you have large tankers (more than 2,000 gallon capacity) the dump tanks tend to be very large. That creates its own set of problems - the larger dump tanks are very heavy and bulky, they require additional manpower to remove from the rig and set up, and most departments don't have that kind of manpower, especially riding on the tankers. The larger dump tanks are also more difficult to store on the rigs, as they require more space. If the dump tank can't be stored low on the rig, it also increases the chances of firefighter injury, as mounting heavy, bulky objects high on the rig makes things more difficult for those who have to remove them.
The answer - carry TWO dump tanks on the larger tankers/tenders. Back in the 1980's, I was a member of a volly department that obtained an ISO-rated water supply system based on a tanker shuttle. We had three 1,200/1,600 gal- tankers, a 2,000 gal tanker, and a 3,000 gal. tanker. We had an 18,000 gal dump tank on the smaller rigs and a 2,200 dump tank on the 2,000 gal tanker. That dump tank was as large as we felt our crews could handle safely and effectively. When we added the 3,000 tanker, we built it to carry a 2,200 dump tank on one side and a 1,800 tank on the other. When dumping, the big tanker dropped both tanks and filled the smaller one half-full, then moved up and filled the larger one (closer to the pumping engine) all the way. We used jet syphons backed up with gravity sypons to move water from the most distant dump tank to the one being used for drafting. It was common for us to supply flows over 1,000 GPM from the tanker shuttle, running over a mile each way to the closest supply source.
We also kept the dump tanks small enough to make handling them reasonable and safe.
We used some other tanker modifications to make this happen, but the ability to dump each vehicle's water without stopping was one of the key elements in this successful program - one which that department still uses more than 25 years later.
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Permalink Reply by Chief Dino on
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I have to agree with Paul and Ben, the ability to keep tankers moving from fill to dump site is crucial. Ben's suggestion of multiple smaller tanks may work. At my Dept, both of our engines have on board tanks of 1000 and 2000 gal and our tankers are 2000 and 3000 gallons. Our 3000 gallon tanker is a converted milk tanker and there is no real efficient way to carry a folding tank. Both 2000 gal tankers have folding tanks of 2000 gal. We practice dropping tanks and dumping at least annually, but in reality ground terrain usually precludes us from setting up drop tanks. Could you squeeze another 2000 gal tank into the mix somewhere, that could be unloaded and set up safely and with minimum personnel?
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