Quick and Dirty Calculator
for Pick-Up Truck Slip-On Units

Here is a simple calculator for estimating the water tank size a pick-up truck can handle.  This is only an estimate!  It may help you choose a chassis.  It might give a starting point before doing more refined calculations.   Some things that will affect the accuracy of this calculation include:

  • the amount of stored items
  • the tank material.
  • the placement of the tank (will the load add too much weight to one of the axles?)
  • will the vehicle be used exclusively on good roads?

We have programmed in occupant weights and some storage.  We suggest you look strongly at using the lower end of the range given.  The high end of the range is possible if lightweight materials are used and storage is kept at minimum.  For the pick-up platforms storage, occupant weight, hose reels and other accessories are a big percentage of the total load placed on the vehicle.  Hence, it is hard to estimate the likely water capacity without knowing more about the unit.  We suggest you use our Slip-on Engine Calculator for a more refined estimate.

Remember to weigh the finished vehicle, fully loaded and ready for operation prior to putting it in service.  Make sure it does not exceed the manufacturers Gross Vehicle Weight Rating or the ratings for either axle.

REC's publications, Slip-On Water Tank Units and Guidelines for Designing Wildland Fire Engines provide additional information.

Estimator for Slip-On Tank Units

Enter the vehicle's GVWR as given by the lbs.
manufacturer.
Enter the weight of chassis or truck prior to lbs.
adding tank, pump and fire accessories.

Expect tank size to range from to
gallons of water.

Roscommon Equipment Center - Wildfire Equipment Research and Development