Maximize a Fire Hydrant's Lifetime
Proper hydrant care - from installation to maintenance - will ensure years of operation. Most important, a well-maintained hydrant will be ready and reliable when it's needed.
Fire hydrants are a critical component of a city’s infrastructure. Although hydrants spend most of their time idle, firefighters depend on their operation to save lives and property. Water operators can extend the life of hydrants through correct installation, regular maintenance, and proper repair procedures.
Hydrants should be properly buried to the marked “bury” line on the lower barrel, just below where the lower barrel connects to the upper barrel. Proper bury depth is important because if a hydrant is struck, it’s more likely to break safely. Extensions or risers are available to ensure proper bury depth. Extension kits can run in 6-inch increments, from 6 inches and up.
Traffic flange and break coupling placement are important, especially when using an extension. The traffic flange protects vehicle operators in the event of collision with a hydrant, as the hydrant will break and fall at the flange location rather than staying upright and increasing the force of impact.
Most fire hydrants are made with iron, steel, brass, and stainless-steel parts. With proper care, a fire hydrant can last a long time. However, because hydrants use so much brass, especially in the connections, proper tools are needed to maintain parts’ durability and longevity. Tools such as pipe wrenches can cause hydrant damage that hydrant-specific tools won’t.
Hydrants should be flushed at least twice each year and should be fully open when flushed. The main valve is made of rubber and seals against a brass seat. Partially open hydrants will pull the valve off the seat just far enough that rocks, stones, and other debris can be caught in the opening, leading to a loose or damaged seal and a leaking fire hydrant. This can result in the main valve having to be replaced or repaired. Over-opening and over-closing also should be avoided, as either action can damage the stem.
Most hydrant bonnets are labeled with the direction of opening the operating nut; if not, the operator manual will have this information. Note that turning the operating nut doesn’t turn the stem inside; instead, the threads in the operating nut push the stem straight down as the operating nut turns, pushing the main valve farther into the waterway.
The act of flushing a hydrant will maintain lubrication of the stem and operating mechanism. As the operating nut separates from the stem, a hole in the operating nut will be exposed, allowing lubrication to enter a cavity inside the operating nut. When the hydrant is closed again, the hole in the operating nut is also sealed off, pushing lubrication from inside the cavity out of the two top holes of the operating nut. The lubrication used on the fire hydrant should be a food-grade oil or grease. Once the hydrant is fully closed after flushing, reverse the direction to release tension off the stem assembly.
Newer hydrants often come with an identification tag to help operators and workers identify the hydrant model and its specific technology, including the model number; steamer, hose, shoe, and connection information; bury depth; year; and paint code. The tag may also provide access to a troubleshooting guide, which can be helpful in the field.
Replacing a Damaged Valve
In cases where a hydrant valve must be replaced because of debris damage, a specific series of steps should be followed to ensure safe, proper replacement. It’s also recommended that safety chains be placed on the hydrant to ensure the caps don’t cause injury from accumulated pressure. The main valve opening size is usually stamped on the upper barrel. The two most common sizes are 4.5 and 5.25 inches.
Once the correct valve size is determined, replacement can be done in the following steps:
- Shut off the water to the hydrant.
- Open the hydrant main valve to confirm the water is shut off.
- Depressurize the hydrant by loosening a cap
- Remove the nuts and bolts on the bonnet and remove the hold-down nut.
- After removing the hold-down nut, check the integrity of the O-ring seals.
- Turn the operating nut to the open position, which will raise the thrust collar. Some hydrants may have a stop nut that will need to be removed.
- Remove the bonnet. When removing the bonnet, take care not to damage any O-ring seals.
- Using a seat wrench, catch the tabs on the main valve assembly and rotate. Breaking the main valve assembly free may require significant pressure; specialty tools can help in this case. Some wrenches allow hookup to a vehicle for more torque.
- Once loosened, pull the stem from the top of the hydrant, which will lift and remove the main valve assembly.
- Remove the valve plate nut (if present) and any gaskets that protect the stem threads from the washer to access the lower valve plate. (In some hydrant models, the valve plate and plate nut are a single piece.)
- Remove the lower valve plate to expose the valve.
- Replace the valve and seat ring O-rings. There are typically two seat ring O-rings: upper and lower.
- Replace the lower valve plate, gaskets, and valve nut. Tighten to the recommended torque.
- Lower the assembly back down slowly into the hydrant. Once lowered, to align the threads with the floating drain ring, turn the stem backward two full turns. A click will sound when the threads are lined up.
It's important for a municipality to know which hydrants have been repaired/inspected or need to be repaired/inspected. Record keeping is an intergral part of any maintenance and inspection program and benefits from more detail than less. It's also important that any issue discovered during an inspection is repaired in a timely fashion. Any fire hydrant deemed inoperable should be clack bagged or tagged to prevent accidental use and replaced or repaired as soon as possible.
Optimizing a Utility's Investment
A good-quality hydrant can be in operation for many years past its warranty if it’s part of a regular maintenance and repair program. Having the right tools and parts on hand will help operators ensure the program is effective. Some manufacturers offer training and support, along with how-to videos, which can be helpful for new employees. For more information, check out AWWA’s Manual of Water Supply Practices M17, Fire Hydrants: Installation, Field Testing, and Maintenance (www.awwa. org/M17).
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