Skid Steer Case Drain Line: What the Third Hydraulic Hose Does

If you've gone to hook up a winch, a high-flow drum mulcher, or another hydraulic attachment and found three hoses where your skid steer or track loader only has two, the third is a case drain line. Most skid steers and track loaders have the standard pair of hydraulic hoses - one male, one female - so that third hose raises questions. Here's what a case drain does, what happens if you leave it off, and what to do if your machine doesn't have a place to connect it.

What is the third hose on a hydraulic attachment for?

The third hose on a hydraulic attachment is a case drain. Hydraulic motors build up internal pressure that has to relieve somewhere, and the case drain line is where it goes. It's basically a relief drain: it sends hydraulic fluid back to the reservoir tank in case the motor starts to overpressurize.

That's the same job whether the attachment is a winch on a skid steer or a high-flow drum mulcher on a track loader. The standard two hoses run the attachment. The case drain is there to protect the motor while it runs.

Can you run an attachment without hooking up the case drain?

Running a hydraulic attachment without the case drain hooked up is not recommended. If the case drain isn't connected, or your machine doesn't have one, the pressure inside the motor has nowhere to go. It builds up over time, and eventually it can blow out the end seal on the motor.

Because that pressure builds over time, a missing case drain won't necessarily cause trouble the first day you run the attachment. That's what makes it easy to overlook, and it's why it's worth checking before the attachment goes to work.

Will a Raytree drum mulcher run without a case drain line?

No. The Raytree drum mulcher requires a third case drain line on the track loader; running it without one can damage the motor. If your machine doesn't have a case drain, it needs one added before you run that mulcher.

Do older skid steers have a case drain line?

Skid steers built before about 2010-2013 generally do not have a case drain line. That's when machines started including a third case drain line, so an older machine, like one from around 2007-2008, likely won't have one.

If you're running an older skid steer or track loader and looking at an attachment with three hoses, check your machine first. If you only find the standard two hoses, plan on sorting out the case drain before the attachment goes on.

Can a case drain line be added to a machine that doesn't have one?

Yes, a case drain line can be added to an older skid steer or track loader. It's essentially just a hydraulic line run back to your tank. Check with your equipment dealer to see what they recommend for adding one to your specific machine.

What should you know about case drain lines before hooking up an attachment?

The third hose is a case drain that protects the attachment's motor, so hook it up every time: running without it risks the motor, older machines may need one added, and your dealer can tell you how.

If you're not sure whether your machine has a case drain or what a particular attachment needs, ask Chupp Industrial before you hook it up.