Rural departments can use dumpsites to maximize water delivery in water-on-wheels (WOW) operations (see “Dumpsite Dynamics,” February issue). Once set up, a dumpsite operation requires some method of transferring water from one porta-tank to another. The three basic options for transferring water between porta-tanks are tank connectors, inchworms and jet siphons.
Performance and data should drive the selection of the most effective option for a given situation, but that’s not always the case. Many departments design their operation based on one of these options and never question how well it really works. The mere suggestion that there might be a better way usually leads to a heated discussion driven by emotions rather than facts. This same type of debate may also occur when it comes to which type and/or size of porta-tank is best.
As I’ve said before, I really don’t care how departments get water from the source to the fire-as long as their systems provide the required delivery rate. If a department needs 1,000 gpm and can deliver it with buckets, that’s fine. However, if the required delivery rate can’t be achieved, the department must search for a better system.
Following is a rundown of water-transfer options.
Figures 2 and 3 show how porta-tank connectors are used. While the idea of this type of water transfer device is sound, one has to ask some questions:
Although some departments use tank connectors, I’m not a big fan of them. They become too cumbersome when more than two tanks are used. And to sustain high flows, three or more porta-tanks are needed.
Another method for transferring water from one porta-tank to another is what has become known as the “inchworm.” Generally, inchworms are constructed of 4″ or 6″ plastic U-shaped pipe. They are used as natural siphons to allow water to flow from the higher level tank to the lower level tank. The inchworm must first be filled with water as shown in Figure 4.
Once the inchworm is filled, the ends are capped and it’s lifted and inserted into the two porta-tanks. When the caps are removed, the water will flow from the tank with the higher level of water to the tank with the lower level (the tank from which the pumper is drafting) as shown in Figure 5.
Although the inchworm can move water from the high side to the low side, before employing it, ask yourself whether the inchworm can transfer the water at the delivery rate required. I’ll discuss that in a later column.
The jet siphon is another tool for transferring water between porta-tanks. As one can imagine, there are many configurations of jet siphons. However, they all make use of the Venturi Principle. A homemade jet siphon is shown in Figure 7. This siphon consists of a 1″ pipe fed by a 1 àƒƒà‚ƒàƒ‚à‚ƒàƒƒà‚‚àƒ‚à‚ƒàƒƒà‚ƒàƒ‚à‚‚àƒƒà‚‚àƒ‚à‚‚àƒƒà‚ƒàƒ‚à‚ƒàƒƒà‚‚àƒ‚à‚‚àƒƒà‚ƒàƒ‚à‚‚àƒƒà‚‚àƒ‚à‚«” hose connection. Three running-board mounts (4 àƒƒà‚ƒàƒ‚à‚ƒàƒƒà‚‚àƒ‚à‚ƒàƒƒà‚ƒàƒ‚à‚‚àƒƒà‚‚àƒ‚à‚‚àƒƒà‚ƒàƒ‚à‚ƒàƒƒà‚‚àƒ‚à‚‚àƒƒà‚ƒàƒ‚à‚‚àƒƒà‚‚àƒ‚à‚«”, 5″ and 6″) provided with 1àƒƒà‚ƒàƒ‚à‚ƒàƒƒà‚‚àƒ‚à‚ƒàƒƒà‚ƒàƒ‚à‚‚àƒƒà‚‚àƒ‚à‚‚àƒƒà‚ƒàƒ‚à‚ƒàƒƒà‚‚àƒ‚à‚‚àƒƒà‚ƒàƒ‚à‚‚àƒƒà‚‚àƒ‚à‚¬” pipe collars and welded metal spokes are carried on the 1″ pipe. These allow the jet to be used on any diameter of suction hose by removing the adapters not required.
Although the jet siphon requires 100-150 gpm to operate, once in the water and pressurized, it can transfer water at a much higher rate (1,000+ gpm) than the inchworm.
Incidents that require 1,000-gpm delivery rates from a water-on-wheels operation for an extended period of time call for dumpsites. To maximize delivery and reliability, multiple porta-tanks must be set up and equipped with effective water transfer devices. Of the three types of devices, jet siphons are generally the most efficient.
In the next installment, we’ll talk more about water transfer devices and how they can be tested and utilized.