If you are not the water supply officer but find your self looking at a pump panel and a lot of hose on either end of your truck, you have as much work ahead of you as the water supply officer. A straightforward hose relay operation is going to start at a hydrant with subsequent trucks laying line from each other until they reach the fire. If the chief in charge of the first due has done his homework, hopefully the structure he is protecting has a preplan involved with it and the water supply officer will give you all the information you need to implement the preplan. At 3 a.m., it will be really easy if the object is to flow 1,000 gpm via six lengths of LDH between each truck with a residual pressure of 25 psi. That means each truck’s discharge will read approximately 67 psi (round up to 70). Unfortunately for the pump operator stuck in the middle of the relay, this is about as much excitement as you’re going to experience unless you can see the fire’s orange glow in the sky. Essential to remember before we discuss hose relays any further is that you never pump LDH at greater than 185 psi.
Several relay valves exist on the market. Your municipality might standardize on one type-which is lucky for you if you don’t have occasion to work with other municipalities. Whatever valve your department or your company uses, you must be familiar with its operation.
Be familiar with whatever adapters you are going to need to put this relay valve in service. Remember that the supply side of the relay valve is the “hydrant.” If you remember that, the confusion involved with connecting to a relay in the middle of the line won’t be as great.
There are times, though, where a truck will lay in from a hydrant and come to find a relay valve sitting in the street connected to a line laid from that point. At 3 a.m., this will foul up even the most seasoned pump operator. Again, remember that the line you just laid is the “hydrant.” Connect the line you laid to the supply side of the valve and you’ll be fine.
Pumping within the relay
It is important to note that in a relay, you are only responsible for supplying the specified volume of water to the truck ahead of you. Know what trucks are behind and ahead of you so you can call them if anything goes wrong. Obviously it also helps to know who is supplying you with water. The attack truck at the end of the relay is the only truck that has to worry about what water appliances are connected to it and at what pressures each needs to be operated. Once you get a relay up and running, you do not have to do anything else unless something goes wrong or until the very end.
Do not do anything until you’re told. Thousands of dollars in equipment stand to be damaged if you do something without being told. In a relay operation, the flow starts at the bottom and ends at the top. At the end, the trucks all shut down in reverse order. You’ll see a fluctuation at your pump panel as the first truck shuts down all its hoselines. This is normal and means you’ll soon be told to throttle down and place your transmission in neutral.
If your chief officers are going to go to the trouble of preplanning for hose relays in your first due, you will probably have to conduct a drill or two to ensure you are going to get the amount of water you expect. These drills are labor intensive and can shut down roadways if you want to do them right. They are highly beneficial though to both new and seasoned pump operators, as well as to potential water supply commanders. Choose a structure that would require a great deal of water to extinguish and go from there. The pumping wizards will love trying to figure out the pressures required to compensate for hills, etc.; apparatus operators will get some practice laying hose; and, most importantly, the powers that be in your first due will find out if they need to tweak their preplans to accommodate unforeseen difficulties in establishing water supply.
Water supply operations are not a glorious part of the job. Quite frankly, they stink-especially if you’re in the middle of the relay. A water supply operation is time consuming to set up, and if you’re not prepared to initiate one, the time involved increases and property is lost. It is critical to practice establishing a water supply as well as commanding one if you are to effectively and successfully establish one.
Chris Mc Loone is FireEngineering.com’s Web Editor. An 11 year veteran of the fire service, he holds the position of First Assistant Engineer for Weldon Fire Company in Glenside, PA. He can be reached at [email protected].