Like many of you, I heard you shouldn’t wash caving rope with a pressure washer because dirt could be forced into the core and abrade the fibers. Bruce Smith at On Rope 1 says this is a myth and challenges us to try it.

I accept. I pulled out an ODR (old, dirty rope)—PMI Max-Wear circa 1992. This rope has seen lots of mud and occasional cleanings. It was last used two weeks before testing.

This rope had a damaged spot (more on that later), so, I cut out a little extra for this test.
The 6′ sample rope has been divided into three sections. One section I will clean with a conventional rope washer, with brush bristles inside. Another section will be cleaned with the pressure washer. The last section will not be cleaned—a control, if you will.

The brush bristle rope washer used for this test.

This is the pressure washer I used. It’s a residential grade Karcher that spews 1500 psi.

Cleaning action!

I ended up getting the sprayer a lot closer to the rope than this pic shows. Actually, I put the sprayer right on the rope. I even tried to cut the rope with the spray. I was unable to do any noticeable damage. Disappointing. I wanted to cut with water. So, I grabbed some webbing and some parachute cord (aka, p-cord, 550 cord). No noticeable damage with them either.

Here’s what the sample rope looks like after cleaning. The pressure washer definitely got it cleaner than the brush washer.

But, where did the dirt go? Did the pressure washer push the dirt into the rope fibers and core?

Time for some surgery. I cut open all three sections to expose the core and the inside of the sheath.

The unwashed section.

The inside of the sheath of the unwashed section.

The core of the unwashed section. Note, the tiny specs on the core are actually dust from my table. I didn’t clean it well enough before the pics.

The brush washer section.

Close up of the inside of the sheath that was cleaned with the brush washer.

Close up of the core of the section cleaned with the brush washer.

The pressure washer section.

The inside of the sheath of the pressure washer section.

The core of the pressure washer section.

Conclusion
None of the samples showed any signs of dirt, mud, silt or any other foreign substance inside the rope. Nothing had made it past the sheath after the pressure washing or even after 17 years of caving. Pressure washing did not drive any dirt into the core of the rope. Of course, PMI caving rope has a tightly wound and thick sheath which undoubtedly helps keep dirt out. I should try this with some looser sheathed rope…

Pressure washing is a great way to get a rope really clean, but it is labor intensive. It took about twice as long to clean with the pressure washer compared to the brush washer.

The small coil was pressure washed. The large coil was washed with the brush style washer.