Water in Hydraulics: A Silent System Killer

[MikePhua]

The Hidden Enemy
Few things worry an experienced equipment operator more than finding water in a hydraulic system. Unlike a visible oil leak or a worn-out hose, water contamination hides inside lines, pumps, and valves—quietly destroying them from within. It dilutes the oil’s lubricating power, causes corrosion, and forms sticky sludge that clogs filters and orifices.
Where Does It Come From?
Water can sneak into hydraulic oil in surprising ways. Condensation inside tanks overnight is a big culprit—especially in machines that sit idle in damp climates. In Northern Canada, for example, a contractor once told how their old log loader’s tank would “sweat” so much during spring thaw that an inch of water settled at the bottom by morning.
Bad seals on filler caps, cracked breather vents, or sloppy maintenance with open hatches in the rain are other sources. Even fresh oil from a poorly sealed drum can carry hidden moisture.
What Happens Next
Once inside, water does three nasty things:

• It promotes rust on pump components, valve spools, and cylinder bores.
  
• It lowers the oil’s lubricity, leading to metal-on-metal contact.
  
• It encourages the formation of sticky emulsions that plug filters and gum up tight passages.
  

An old mining crew in West Virginia once traced sluggish loader hydraulics back to milky oil thickened by water. Replacing the oil and flushing the system saved the day—after they’d replaced a pump that the contamination had already wrecked.
How to Spot the Signs
Milky or cloudy oil is the tell-tale sign. If oil on a dipstick looks like chocolate milk or a latte, it’s carrying water. Tiny bubbles, foamy residue, or filters clogging too soon are also warnings.
In modern shops, an oil analysis can pick up water content long before you see any symptoms. Many big fleets pull samples every few months—saving thousands by fixing small leaks or replacing bad breathers early.
What to Do About It
Prevention is king:

• Store oil indoors and sealed tight.
  
• Check breather caps and tank covers for cracks.
  
• Drain water traps and sumps regularly, especially on machines working in wet conditions.
  

If water is found, it must be removed quickly. For small amounts, running the machine warm with the tank open (in a dry place) sometimes lets moisture evaporate. For larger contamination, draining, flushing, and filter replacement are the only safe options.
One rail contractor in the UK famously rigged up a homemade vacuum dehydrator for their aging tamper fleet. They ran oil through heated coils and a vacuum chamber to pull out dissolved water—keeping ancient machines alive until budget arrived for replacements.
A Reminder from the Field
In 2019, an airport ground crew in Alaska accidentally left a fill cap open during a storm. Water poured into the hydraulic tank of a snow blower. Days later, the frozen slush cracked a line, sprayed oil across the runway, and caused a major flight delay—an expensive lesson in the true cost of moisture.
Summary
Water in hydraulics is an invisible threat that strikes silently but hits hard. Good storage habits, careful inspections, and quick response are the best defense. In a world where one drop of water can ruin a $20,000 pump, a little vigilance goes a long way.