Cold Weather Operations

If you are looking at this article, we can only assume you are one of the many individuals who are seeking information on whether they should run a “dry’ or a “wet” pump during cold weather operations.

This article covers the Waterous recommendation along with several other “pros” and “cons” related to running the pump “dry” or “wet” in cold weather environments.

The Waterous’ recommendation for cold weather operation of Waterous Fire Pumps is simple: “If the pump is exposed to freezing temperatures, drain all water from pump, lines and accessories”. Is it really that simple? Read on…


If the fire department elects to run a “dry” pump during cold weather conditions it is necessary to drain the pump completely. To properly drain the main cavity of the fire pump, the tank to pump and tank fill valves need to be closed and the main pump drain opened and remain opened until the water is drained out.

If the tank to pump and/or tank fill valve(s) are leaking, the pump will not remain drained. Leaving the drain valve open while the apparatus is parked will keep the pump dry, but will also allow the booster tank to drain down, requiring someone to periodically monitor the water level in the booster tank between uses. In addition, leaving the drain valve in the open position while it is subjected to freezing conditions may cause it to freeze in the open position, which could render the pump inoperable.


A “dry pump” is not necessarily dry. Discharge and intake (compound) gauges, gauge lines, individual drain lines, pressure lines and other components with small orifices will have a tendency to retain water. Unless they are disconnected and allowed to drain they may retain water, resulting in freezing and subsequent damage to the components. Since disconnecting and draining of the lines is labor intensive, this practice is seldom if ever done. This promotes the need for pump house heaters and under body pump house enclosures when operating in climates where freezing conditions are a concern.



  • Minimal chance the pump is going to freeze.
  • Opportunity to ensure that the tank to pump and tank fill valves are sealing properly.
  • Ideal for situations where extended response distances to and from the incident and/or increased speeds (highways, freeways, etc.) are obtained. With no water in the main cavity of the fire pump and its accessories little if any damage will occur.


  • Requires periodic opening of the main pump drain to ensure the main pump cavity isn’t partially full of water. A partially full pump will freeze rapidly and will initially cause damage to the impeller shrouds and vanes. This damage is unable to be seen until the fire pump requires disassembly. Other signs of damage may be vibrations and/or metallic sounds coming from the pump, water externally leaking from the main fire pump body and/or body halves, water leaking from components attached to the fire pump or a failed annual pump service test.
  • If the main pump drain is left open and the tank to pump and/or tank fill valve(s) are leaking, the apparatus booster tank may be low or empty. This condition requires constant monitoring and filling of the booster tank. Also, an open drain can freeze in the open position.
  • If the pump is left “dry” for extended durations without the fire pump being operated, an excessive build up of calcium and/or rust deposits will accumulate inside the main fire pump cavity. The amount of build up is further compounded by the water quality for the department. Once the fire pump is engaged and water is circulated the excessive build up is broken loose and may create problems with the discharge relief valve system (plugged strainer screen), scoring to the discharge valve seats, damage to the individual discharge valve drains, damage and scoring to the priming valve and other accessories that utilize o-rings and/or seals on mating surfaces. It is important to operate the fire pump periodically to minimize the chances of this condition occurring.
  • Priming of the fire pump may be required.