Time for another of the great "less filling, tastes great" debates within the fire service: Should a department run a dry or a wet pump during cold-weather operations?
To get to the bottom of this, I went to the mountain so to speak and talked to the good folks at Waterous, who've been building fire apparatus pumps since 1886.
The simple answer from the pump pros is that all water should be drained from the pump, intake and discharge lines, and accessories like gauges. The simplest answer, however, might not be the best answer for your department, so keep reading.
If your department elects to run a dry pump during cold-weather conditions, you must drain the pump completely. The cavity of a typical centrifugal pump contains 25 to 30 gallons of water; the intake and discharge lines and drain lines account for additional water. The main drain valve — the main pump drain — on most fire apparatus pumps is usually a ½-inch valve, so it takes more than a few minutes to completely drain the pump.
Start the draining process by ensuring that the tank-to-pump and tank-fill valves are both closed and the main drain valve is completely open. One good reason to conduct a pump-draining exercise for all of your pumping apparatus before the first cold weather arrives is that the tank-to-pump and tank-fill valves are notorious for developing leaks.
If either of these valves is leaking, the pump will not stay drained regardless of how thoroughly you drain it. Early discovery gives you time to get the proper repairs completed before you start running calls in sub-freezing temperatures.
To enhance the draining process, uncap and open all intake and discharge lines going in and out of the pump. Also, open any drain lines that serve pump gauges if your pump.
Develop a step-by-step checklist for all the pertinent valves that need to be opened (for draining) and later closed (before the apparatus rolls on the next call) for each piece of apparatus in your fleet.
Don't just list broad items like, "Drain all intake line." Instead, list all valves individually so that those doing the draining know to open all the valves and then close those same valves.
Hot running water
The modern pumps found on fire apparatus have numerous discharge and intake gauges, gauge lines, individual drain lines, pressure lines and other components with small orifices that have a tendency to retain water. These smaller components can freeze when they've not been properly disconnected and drained.
Draining these pump components, however, is labor intensive (Read: Pain in the "bazooka") and seldom gets done.
One remedy for this potential problem is to have a pump house heater installed to help to keep gauges and lines above the pump from freezing. The pump house is the enclosed area surrounding the fire pump and its accessories.
Pump house heaters are an auxiliary component consisting of a heater cores and fans. The heaters are usually written into the apparatus specifications and are commonly found on apparatus in cold-weather climates.
The main purpose of the pump house heater is to provide limited freeze protection to the gauges, gauge lines and other small components that are located in the upper area of the pump house. They do little to protect the fire pump or the lines or valves beneath the fire pump.
Another good measure is to have a metal under-body pump house enclosure, such as belly pans, heat shields, etc. These enclosures are designed to close off the underside of the fire pump, thereby reducing cold airflow from reaching the pump from below. The enclosure is installed below the vehicle exhaust stream to capture heat and keep it around the lower part of the pump and protect those components from freezing.
First rule of pump club
The first rule for wet pumps in sub-freezing weather: Engage the pump and circulate water because moving water doesn't freeze. Your fire apparatus operators need to be skilled and practiced in circulating water between the booster tank and the pump whenever they are not actively flowing water out of the pump to supply hose lines, deck guns, etc.
The process looks like this:
- Fully open the tank-to-pump valve.
- Partially open the tank-fill valve to allow adequate circulation — approximately 1/8 to 1/4 from fully closed.
- Continually monitor the pump temperature by feeling the intake fitting with a bare hand to ensure the pump isn't overheating.
An electronic monitor that gauges the pump's water temperature is a feature that's increasingly being added to fire apparatus pumps as a means to prevent overheating. The apparatus operator should be cognizant of this feature if their pump is so equipped.
An illuminated warning light indicates that the water temperature within the fire pump and apparatus booster tank is overheating and the pump must be disengaged or fresh water must be introduced into the pump. Failure to do so can result in severe damage to the fire pump and its components.
I came across a really neat training video on this topic that was produced by the Boone County (Mo.) Fire Department. They include temperature ranges for various actions for their personnel to take to protect the pumps.
- Between 32 and 16 degrees F.: No variance from normal operating procedures except for recirculating water in pumps while on scene.
- Between 15 and 0 degrees F.: Required recirculation of water in pumps while on scene.
- 0 degrees F and colder: All pumps drained according to protocol while in quarters. All staged responding units maintain dry pump status. All units positioned for pumping or potential pumping fill the pumps and recirculate water between tank and pump when not actively discharging water.
- For pumpers, remove all caps and plugs after arriving on scene. Water can leak by valve seals and then freeze into a 2 ½-inch diameter block of ice, rendering the valve inoperable.
Once hose lines are charged, they should never be completely shut off. Hose lines can freeze within minutes. Inform all firefighters to allow their nozzles to continue to flow some water, especially after the emergency is through.
For the smaller pumping apparatus like Type III engines or brush trucks, place an open hose line nozzle into the water tank and start the pump engine, if so equipped. The pump operator should watch the pump gauges carefully because they may begin to freeze.
Some operators feel that changing the water pressure allows the gauge bellows to move and water in the gauge lines will also move which may delay freezing.
Also, don't forget to drain front intakes on pumpers and aerials. Aerials must have their waterways drained after they are charged.
Failure to drain the waterway after the flow of water stops can result in them freezing very quickly — think about how bridges freeze before roadways because of the cold air reaching surfaces above and below. Attempting to lower an aerial with a frozen waterway is surefire recipe for serious damage to the waterway and an equally serious repair bill.