The first hard freeze is the most expensive day of the year for a lot of spray rigs. Water left in a diaphragm pump, a fitting, or a hose reel swivel expands as it freezes, and in spring you find out the hard way: a cracked pump head, a split fitting, a reel that leaks at the joint. Winterizing takes under an hour and a few jugs of antifreeze. Replacing a pump and fittings in April costs a lot more than that.
This guide is written for the two-tank skid most of our dealers run: a gas engine driving an AR45 diaphragm pump, with a suction transfer hose, a return valve for each tank, and a hose reel to the gun. If your rig is plumbed differently, the ideas still apply, but your pump manual and your rig builder’s instructions come first.
This isn’t a guarantee or a one-size-fits-all procedure. It’s the set of guidelines our rig builder, pump makers, and experienced operators keep coming back to. Follow them carefully and you give your equipment the best shot at coming out of winter in one piece.
Step 1: Get your material out of the rig
Before anything else, empty both tanks. Any product left in the tanks, pump, or lines over the winter is exposed to freezing temperatures and sits there for months doing nothing for you.
- Use a transfer pump or your suction transfer hose to move leftover material into clean, sealed totes or barrels you can bring inside.
- Store them indoors where they stay above freezing, up off the concrete on a pallet, and away from heaters or direct sunlight.
- Label every container with what’s in it and the date, and keep the SDS with it.
- Never top off stored material with anything that has run through the system during winterizing. Antifreeze and product don’t mix.
Step 2: Flush with clean water
Put fresh water in the tanks and run it through the pump, both return lines, the hose reel, and the gun until it comes out clean. You don’t want product residue sitting on the pump’s diaphragms and valves all winter.
Step 3: Inspect the unit and do your maintenance
Winter downtime is the best time to fix things, because the rig isn’t costing you jobs while it’s apart. Before you put it away, go over it for broken or worn parts:
- Hoses: cracks, soft spots, abrasion, and leaks at the crimps.
- Fittings and clamps: drips, corrosion, or anything loose.
- Hose reel: swivel leaks and a reel that turns and locks the way it should.
- Gun and tips: worn tips, a sticky trigger, or leaks at the gun.
- Pump and engine: oil leaks, belt or coupling wear, and anything that sounded off during the season.
Order the parts now and do the repairs over the winter, so the rig is ready on the first good day in spring.
Step 4: Use the right antifreeze
Use propylene glycol RV antifreeze (the pink, non-toxic kind). A few things to watch for:
- Skip the ethanol-based RV antifreeze. Alcohol is a solvent and gives the pump no lubrication. Check the label for propylene glycol.
- Don’t use automotive antifreeze. It’s toxic, it’s a disposal headache when you flush in the spring, and distributors warn it’s hard on seals in this kind of equipment.
- Don’t dilute it. Mixing it with water raises the temperature it protects to, and you lose the margin you paid for.
- Buy enough. Between the pump, plumbing, and a full hose reel, plan on roughly 15 gallons for a two-tank rig.
Step 5: Run antifreeze through the system
This is the method our rig builder recommends for these skids. It works the same way you fill your tanks:
- Drop the suction transfer hose into a bucket of RV antifreeze.
- Open the Tank 1 return valve.
- Start the engine and squeeze the trigger until pink antifreeze comes out of the gun.
- Switch the return valve to Tank 2 so that line gets antifreeze too.
- Shut the engine off.
No transfer pump? Pour the antifreeze into one of your tanks instead and run it the same way: start the engine, squeeze the trigger until pink comes through the gun, and switch the return valves so each line gets antifreeze.
Keep the bucket topped up as you go so the pump never sucks air. When you’re done, the pump, both return lines, the hose, and the gun should all hold pink fluid. Leave it in there. Pump makers recommend storing diaphragm pumps with RV antifreeze inside them, not just drained.
Step 6: Relax the pressure
Back off the pressure regulator on the pump’s control unit and leave ball valves partly open. Valves and regulators left tight all winter can stick at startup.
Step 7: Take care of the engine and pump
- Add fuel stabilizer and run it through, or run the carburetor dry.
- Change the engine oil before storage, not after.
- The AR45 is a semi-hydraulic diaphragm pump with its own oil reservoir. Check the oil level and color. Milky or cloudy oil usually means a diaphragm is leaking, and winter is the cheapest time to fix it.
Step 8: Store it inside if you can
The surest protection is keeping the rig in a heated or temperature-controlled space. If you can do that, do it, and still run antifreeze through it as insurance in case the heat goes out.
Step 9: Tag it
Hang a tag on the rig that says “Winterized: flush before use.” It takes ten seconds and keeps anyone on your crew from loading product on top of a system full of antifreeze.
What about just blowing the lines out with air?
Compressed air is fine for clearing water out of hoses, but don’t count on it alone for the pump. Diaphragm pumps have pockets and check valves that hold water even after a good blowout. If you use air, keep the pressure low around the pump and follow it with antifreeze.
Caught by a cold snap?
If you’re still spraying and a freezing night is coming, park the rig somewhere heated. And if you think the pump may have frozen, don’t start it. Let the whole rig thaw completely first. Running a pump with ice inside it can finish off what the freeze started.
Spring startup
- Check the pump oil and the engine oil.
- Flush every line with clean water, through both return lines and the gun, until there’s no pink left.
- Check hoses, fittings, and the reel swivel for cracks or leaks before you load product.
- Bring your stored material back out, check it before loading, and you’re back in business.
Quick checklist
- Material moved into sealed totes or barrels and brought inside
- System flushed with clean water
- Unit inspected; worn or broken parts ordered or replaced
- Propylene glycol RV antifreeze run through both return lines and the gun
- Pressure regulator and valves relaxed
- Fuel stabilized, engine oil changed, pump oil checked
- Rig stored inside if possible
- Rig tagged “Winterized: flush before use”
The bottom line
There’s no magic trick here, just steps that are easy to skip when you’re tired at the end of the season. Get the material out and inside, get the water out, get antifreeze into every place water could sit, and keep the rig warm if you can. If you have questions about your Ugly Roof rig, give us a call.
