by Bill Kleiman

This post is for those who spray water on prescribed fires.

On our piston pump units we often use the above JD-9 Green Guard nozzle. We like it because it is easy to hold, especially while driving in a UTV. This nozzle is expensive at over $200. I first unscrew and remove a 3/4 to 1/2 inch reducer fitting that comes on the gun. I am touching that reducer. With the reducer removed the half inch hose fitting thread direct to the nozzle.

If you have one of these look at how it is attached to the hose. Here I am touching a swivel built into that hose fitting. When you buy hose ask for swivel fittings at both ends of the hose. They help with reeling up hose. At the nozzle end of the hose the swivel helps reduce how much you struggle with the hose.

In this case above the hose did not come with a swivel, but an even better swivel was added in the brass half inch fitting. It swivels easier but the fitting is expensive at over $30.

The Hypro D30 piston pumps we use produce a little under 3-4 gallons per minute at high pressures of 150-350 psi. We use the extra large tip on the right. You have to ask for this tip when purchasing the nozzle.

PISTON PUMPS VS CENTRIFUGAL PUMPS

The half inch hose and JD-9 nozzle are for piston pumps, or sometimes they are called piston/diaphragm pumps. These pumps produce low flow but high pressure. They are unique in that they only produce one flow rate no matter how big or long the hose is. With the Hypro D30 piston pump model a 300 foot hose produces 3-4 gpm of flow, the same as a 50 foot hose. The pressure at the nozzle is also the same on both hose lengths. The benefit of these pumps is you can use long light weight half-inch heat resistant hose which are great for un-reeling hose to get water where you want it.

The piston pumps are also stingy with water. This model only does 3-4 gallons per minute max. If you took the nozzle off entirely it would flow at 10 gpm at a very low pressure.

Compare this to a centrifugal pump. Centrifugal pumps can produce very high flows but the pressure is quite low with a 5 hp motor, say 30 to 70 psi. I won’t try to explain the physics of centrifugal pumps but the following points are important and often overlooked. With centrifugal a half inch diameter hose will produce a ton of friction to the water and diminish the flow and pressure that hose can carry. So these pumps tend to come with 3/4 inch or 1 inch hose diameters. This means your hose is heavy, and your reel likely fits a lot less length of hose than the piston pump units. If you do try a half inch hose with these centrifugal pumps keep it short on a separate line from the reel, often called a whip line.

The centrifugal pump is the standard in wildfire operations. A high flow is no problem if you are on a creek pumping water that does not run out. Or perhaps you are pumping from a very large fire truck tank where you can can pump 10 to 50 gallons per minute at modest pressure for a long time. On a UTV you will run out of water quick.

Prairie burners like the piston pumps for low flow, high pressure, and small droplet sizes. They do need freeze protection for overnight storage.

How to freeze protect a piston pump: Drain tank, spray empty, add maybe a gallon of pink antifreeze and pump the pink through the nozzle into the tank. If the night is not too far below freezing you can dilute the pink a bit. Some reuse the pink by spraying it into a jug. The pink stuff freezes at times but does not expand and break parts. An unheated shed can offer some freeze protection. The freezing overnight will occur in the hose reel, fittings, then the pump and last the tank.