Water is key to any firefighting operation. Being able to secure an adequate water supply is critical a critical skill for all fire departments. One of the most challenging scenarios to secure a water supply in is when there is no municipal water supply, or it is lacking in volume and flow.
When fires occur in these areas, the only alternative is to shuttle water from the nearest municipal supply or a static body of water. To get the highest flow possible, departments must train on shuttle setup and equipment to analyze where improvements can be made.Water supplies should be evaluated based on the largest fire hazard in the area using the source
A smoothly operating high-flow water shuttle takes pre-planning and training. A goal of training is to find the bottlenecks (constraints) in the system limiting flow. The theory of constraints is an approach to process optimization use to identify bottlenecks, then eliminate the bottleneck or adjust the process to meet the speed of the bottleneck.
The only way to improve the process output, in this case fireground flow rate, is by improving bottlenecks. Improving non-bottlenecks does not improve the process output. Training provides the opportunity to identify and correct bottlenecks. The following examines some common constraints of a water shuttle.
Identifying A Water Source
The time to identify a water source for a fill site is not when the alarm bell goes off. Water supplies identified for fill sites must be able to provide the target fill rate of 1000 gpm. Natural bodies of water must be evaluated during different times of the year This is based on the restrictions placed on ploy tanks of 100psig inlet pressure and 1000gpm inlet flow. It is possible to fill none poly tanks at faster rate if designed for it, but there are less chance for mistakes if the fill rate is standardized at 1000gpm.
Along with flow, adequate volume must be available at the fill site. Water supplies should be evaluated based on the largest fire hazard in the area using the source.
Another way to evaluate the minimum volume is the ISO standard. A shuttle must be able to maintain a flow of 250gpm for two hours. This requires a water source to have a minimum volume of 30,000 gallons. Natural bodies of water must be evaluated during different times of the year to make sure the minimum volume remains adequate.
Know Your Flow Rates
Normally, using a municipal hydrant system is a good choice for a fill site as it has significant water supply to support a fill site operation. A large or extended fire has the potential to deplete smaller water systems. Some hydrants easily flow over 1000gpm yet other hydrants in the same system may flows less than 1000gpm It is important to know the system capacity when using a municipal supply for tanker operations. Flow from the hydrant can be another constraint at the fill site.
Some hydrants easily flow over 1000gpm yet other hydrants in the same system may flows less than 1000gpm. Knowing the flow rate of hydrants used for a fill site is a critical component of fill site pre-planning.
| Dry hydrants are the most efficient way to access static water supplies |
Static Sources And Dry Hydrants
Static sources can provide a good water supply for filling tankers if the volume is adequate and there is access. Access to a static water supply can be done in several ways, pre-planning will allow the most effective and efficient means to be used when water is needed. The most efficient way to access static water supplies is by installing a dry hydrant from the water source to an area an engine can easily access.Dry hydrants minimize the equipment, time, and personnel needed to start drafting operations at the fill site
Dry hydrants minimize the equipment, time, and personnel needed to start drafting operations at the fill site. If a dry hydrant is not installed, a strainer must be connected an adequate amount of suction hose to reach the water. Most engines carry two 10-foot sections of suction hose, this limits the distance between the engine and water source without collecting additional suction hose from other apparatus.
The amount of suction carried on engines was tied to the limitation of motorized primers. These primers had the potential for the motor to burn out if operated for the extended period to prime more than 20 feet of 6” suction line. With the advent of air driven primers, it is possible to prime significantly more than 20 feet of 6” suction without equipment failure.
| If the volume is adequate, static sources can provide a good water supply for filling tankers |
Dump Tank And Pumps
The fill rate must be reduced to allow the portable pumps to keep level of the dump tank during tanker filling Portable pumps can access water supplies that are out of reach of standard engines. Setting up a water supply with portable pumps requires a significant amount of equipment and personnel. To get the desired 1000gpm fill rate, an open relay to supply an engine is normally constructed.
The dump tank(s) used for the open relay and the engine’s tank must have sufficient capacity to fill the largest tanker in the shuttle at 1000gpm. If this is not the case, the fill rate must be reduced to allow the portable pumps to keep level of the dump tank during tanker filling or add more pumps to increase the supply to the open relay.
Moving The Fill Area
If tanker traffic flow is smoother in an adjacent area, the fill area should be moved The physical layout of the fill site can become a bottleneck. It must be large enough to allow two tanker to be positioned for filling. Traffic cones are used to mark the spot where each tanker must stop for the fill lines to reach. If the area is overly congested with the engine and tankers, the area for filling the tankers must be moved.
This is facilitated by using LDH to make the fill site remote from the fill engine. Even if the site is large enough to allow the tankers to be filled near the engine, the flow of traffic may be less than optimal. If tanker traffic flow is smoother in an adjacent area, the fill area should be moved. When designating the tanker filling areas traffic flow is a major consideration. The site should be such that no maneuvering is needed, but if it is required the tankers do so when empty.
| The physical layout of the fill site must be large enough to allow two tankers to be positioned for filling |
Tankers At The Fill Site
Ideally tankers are filled with two 2 ½” or 3” lines. Some new tankers are equipped with LDH fill connection. If the plumbing downstream of the connection is large enough to support the fill rate neither of these connections will restrict fill rates.The plumbing between the hose connection and the tank is a potential for bottleneck of the goal of 1000gpm
The plumbing between the hose connection and the tank is a potential for bottleneck of the goal of 1000gpm. Tankers with a single non-LDH fill connection will struggle to meet the target fill rate. This bottleneck may be difficult to overcome without major redesign of the tanker.
Two Ways Lines
There are two ways lines at the fill site are normally laid out: running 2 ½” or 3” lines from the individual discharges of the engine or running the 2 ½” or 3” lines from a water thief manifold fed by LDH from the engine. Both have advantages and disadvantages. Using individual discharges will require more hose to reach both fill stations.
The location of the discharge may require the operator to be standing next to pressurized line. The opening and closing of the discharges will place added wear on the engine’s valves. Using two 2 ½” discharges will allow the desired fill rate of 1000gpm without overloading the capacity of each discharge.
| Two 2 ½” discharges will allow the desired fill rate of 1000gpm where individual discharges would require more hoses |
If the LDH is supplied from a 2 ½” discharge with an adapter, it is highly likely the goal of 1000gpm may not be met A water thief fed with LDH provides the option to place the fill lane and the water supply a distance apart. The water thief lets an LDH line be added to fill tankers equipped with LDH fills. The biggest disadvantage is the ability to achieve 1000gpm depending on how the LDH is fed. Engines with true LDH discharges will not have an issue supplying the LDH at 1000gpm.
On the other hand, if the LDH is supplied from a 2 ½” discharge with an adapter, it is highly likely the goal of 1000gpm may not be met. This situation can be improved by using a siemese or trimese to feed the LDH for multiple 2 ½” discharges on the engine. Many factors go into selecting the best fill site configuration for a department, it is critical to train and test in order to determine what is most effective and efficient for your department.
| Manifold systems being set up and operated |
Choose The Right Place For A Dump Site
The dump site is the equivalent to a fire hydrant, except it takes a larger footprint and can be placed where it will provide the best benefit to the fire ground. This might mean setting the dump site a distance from the fire ground and supplying the attack engine using LDH.Tankers must be able to maintain a steady flow through dump site without unneeded maneuvering
It is more important placing the dump site where the best flow of tankers can be obtained. Tankers must be able to maintain a steady flow through dump site without unneeded maneuvering. Setting up a dump site in an intersection provides additional room to keep things moving at the dump site.
Dump tanks impact the overall flow of the shuttle in several ways including footprint and capacity. Real estate is a precious commodity at a dumpsite. It may be necessary to place the dump site a distance from the fireground to have enough room to set up tanks and provide a smooth flow of traffic. The larger the tank capacity, the larger the footprint.
Sometimes the tank can be wider than the road, for example a 3000-gallon tank is 14’x14’. This presents a problem when trying to setup on a narrow country road or a congested city street. A solution to this is using the single lane style tank that is 8’x14’ for 2100-gallons and fits nicely in front of or behind the supply engine. Larger tanks also leave more water in the bottom once the limits of the low-level strainer is reached.
| Tankers maintaining a steady flow through the dump site without unneeded maneuvering |
Single Or Multiple Dump Tanks?
Using multiple dump tanks increases the flow at the fireground, but requires transferring the water from the secondary to the primary tank There must be enough space at the dump site to add dump tanks should additional capacity be needed. If there is no place for tankers to dump, tankers will back up waiting for room in the tank. The easiest way to maintain flow is adding an additional dump tank.
Not only must the area have room to add additional tanks once available, the tanks must be spaced out to allow two tankers to dump at the same time. This will increase the flow of the shuttle by keeping tankers moving and putting more water at the dump site. The space also provides a safe area for fire fighter working at the dump site.
Using multiple dump tanks is needed to increase the flow at the fireground, but it requires some method of transferring the water from the secondary tanks to the primary tank. This has the potential to create several bottlenecks. For efficiency, water should always be transferred from the secondary tank to the primary tank.
| Ladders can be used as a bridge over the middle tank to run the transfer hose over to the primary tank |
When there is another tank between the secondary and primary tank there is the temptation to flow water into the middle tank before going to the primary tank. This is extremely inefficient. A ladder can be used as a bridge over the middle tank to run the transfer hose over. This allow the secondary tanks to have roughly the same available capacity when tankers dump which is important when dumping more than one tanker at a time.A ladder can be used as a bridge over the middle tank to run the transfer hose over.
Appropriate Use Of Jet Siphons
Jet siphons are commonly used to transfer water into the primary tank from secondary tanks. Along with transferring water between tanks, it is possible to us multiple intakes form the pump going to secondary tanks.
Multiple dump tanks require multiple jet-siphons to transfer water to the primary tanks. Each jet siphon requires water from the engine to drive it. Jet siphons can take up to 300gpm each to transfer water at rates over 750gpm.
| Jet siphons require water from the engine to drive it and can take up to 300gpm each to transfer water |
Dump sites are tight, while we may want to bring in a second engine to transfer water it just will not fit most of the time The water used to drive the jet-siphons takes away from the pump capacity available to supply the fire ground. With a 1250gpm engine at the dumpsite, using a single jet siphon has the potential to reduce the available capacity of the pump to 950gpm. One way to address this problem is by testing jet siphons to determine the most efficient ones in inventory.
The other way is by using a secondary pump to transfer water. Dump sites are tight, while we may want to bring in a second engine to transfer water it just will not fit most of the time. This is when small grass trucks and portable pumps come into play. Both options take up much less room than a full-size engine. Most small pumps have the capacity to drive jet-siphon. It is important to train with this setup to insure the pump can adequately drive the jet-siphons.
Use The Strainer Correctly
One thing many people fail to recognize as a bottleneck is the low-level strainer. The strainer that has been on the truck for decades is viewed as being fine, it has always worked. In reality, old low-level strainers were designed and optimized at a time when 750 and 1000gpm pumps were the norm, not the 1250gpm and up pumps in use today.
| |
| An old strainer with a front intake can restrict the pump capacity to less than 50% |
Couple an old strainer with a front intake as we had at a recent drill, and the pump was restricted to less than 50% capacity Couple an old strainer with a front intake as we had at a recent drill, and the pump was restricted to less than 50% capacity. Fortunately, there a new design strainer was available which allowed the pump to reach 80% capacity. While flow is important when evaluating a low-level strainer, how low the water can be pulled before taking in air is also a primary consideration.
A strainer that flows over 1500gpm but leaves 12” of water in the bottom of the tank will eventually cause a bottleneck in the shuttle. There needs to be a balance between maximum flow and maximum extraction capability when evaluating strainers.
| Old low-level strainers were designed and optimized at a time when 750 and 1000gpm pumps were the norm |
Supply Engine At The Dump Site
The engine with the largest pump must be the supply engine at the dump site Depending on the design, the engine can be the bottleneck to the flow available to fireground. The engine with the largest pump must be the supply engine at the dump site. Even though the largest pump is used, the available flow can be reduced depending on which intake is used.
For mid-mount pumps, the side intake provides the highest flow as the water goes directly into the pump. It is common for engines with mid-mount pumps to have front and/or rear intakes. Using these inlets at the dump site allows the engine to be in line with the dump tanks to create a lower profile but this come at a cost.
| It is common for engines with mid-mount pumps to have front intakes |
Another solution is using a 90-degree elbow from the side intake to go to the front or rear of the engineThese inlets will provide less than the rated capacity of the pump due to additional losses in the plumbing. Front intakes can restrict the capacity around 50% while the rear intakes can cause a restriction of 25% or more. A solution to this is bending the suction hose from the side to the front or rear, but this will use an entire section of hose just for the bend.
Another solution is using a 90-degree elbow from the side intake to go to the front or rear of the engine. Elbows with a large radius provide minimal impact to the capacity of the pump and does not waste a section of suction for the bend.
| Rear intakes can cause a restriction of 25% or more and a solution to this is bending the suction hose from the side |
Stationary Tankers Can Be A Problem
A line of tankers waiting to dump points to the dumpsite as the bottleneckA stationary tanker is an indication of a bottleneck in the system. Where the tankers are standing still points to the location of the bottleneck. If they are waiting to get filled, the bottleneck is the fill site. A line of tankers waiting to dump points to the dumpsite as the bottleneck.
This might mean establishing a second fill site or adding a tank at the dumpsite. Running out of water at the dump site means there is a bottleneck somewhere, if tankers are moving there are not enough for the length of the shuttle route. High-flow shuttles requires continuous evaluation to key water flowing smoothly and make adjustments when needed.
As your tanker shuttle is examined in detail other bottlenecks may present themselves. The ones presented here are the more common ones departments have experienced. In order to identify and fix bottleneck, shuttle training on a regular basis is a must. Once a year is the minimum.
The more you can train with all the departments that would be involved in your water shuttle the better. Tools to help plan and determine the flow rate of your water shuttle can be found at Ohio Fire Chiefs Water Supply Technical Advisory Committee.