Why Is Ink Draining Into the Waste Tank After Installing a New Capping Station on Your Epson Printer?

Question:

I installed a new capping station on my Epson printer, and initially everything worked well. But after just a few prints, the black ink stopped printing—and then I noticed that all the ink had drained into the waste tank while the printer was turned off. What would cause this? Is it possible that the new capping station isn't sealing correctly?

Answer:

💧 Why Your Ink Might Be Draining Into the Waste Tank

Let’s start with the most likely causes based on your description. If ink is freely draining into the waste tank—especially while the printer is off—there are typically two potential culprits:

✅ 1. Ink System Siphoning (Most Common Cause)

Even if your capping station installation seemed perfect, the actual cause of ink draining into the waste line is more often due to siphoning within a closed-loop fluid system. Here's what that means:

• If you're doing wet capping (i.e., filling the capping station with cleaning solution or water), and

• Your waste tank is lower than your ink tanks, and

• Your ink system is fully connected (forming a sealed path from tank to printhead to waste line),

…then gravity and siphon action can pull ink into the waste tank even when the printer is off.

This isn’t a fault in the capping station itself—it’s a fluid dynamics issue. Essentially, you’ve accidentally built a siphon.

✅ 2. Ink Tank Position and System Type

Depending on what type of ink tank setup you're using, the risk of siphoning changes:

If you're using a barometric tank (gravity-fed):

• Make sure the tank level is not too high relative to the printhead.

• If the tanks are too elevated, ink will flow downward naturally—especially if dampers are weak or worn out.

➡️ We have a guide that explains how to properly prime and level barometric CIS tanks here:
How to Prime CIS Tanks – BCH Blog [https://bchtechnologies.com/blogs/news/how-to-prime-cis-tanks]

If you're using a non-barometric system with dampers:

• Ink siphoning is less likely unless dampers have failed or the tanks are significantly above the printhead level.

🔍 Could It Be the Capping Station?

It's still worth verifying whether your new capping station is sealing correctly. A leak in the capping station could result in failed cleanings or poor suction—but usually not full ink drainage. However, here's how to test for a proper seal:

🧪 Capping Station Seal Test:

1. Install a pressure gauge to the waste tube.

2. Draw air from the waste line using a syringe or pump.

3. A properly sealed capping station should register >10 kPa of vacuum pressure.

You can find our full pressure testing kit here:
Pressure Gauge Kit for Epson L1800/1390-based DTF Printers
[https://bchtechnologies.com/products/pressure-gauge-kit-for-epson-l1800-1390-based-dtf-printer-diagnose-optimize-your-printhead-performance]

If the pressure reading is too low, the cap might not be sealing properly, which can cause clogging or cleaning failures—but it wouldn't usually cause full ink drainage unless combined with the siphoning conditions mentioned earlier.

🛠️ How to Prevent This Moving Forward

• Avoid filling the capping station with fluid unless you're doing a soak with the waste line clamped.

• Keep the waste tank level above or equal to your ink tanks when the printer is off.

• Use proper dampers and ensure they’re sealing correctly.

• Verify ink tank placement to avoid excessive gravitational pull.

• If you're doing overnight soaks, consider disconnecting the waste tube temporarily or clamping it shut.

Dealing with printer problems like this can be tricky because they often require hands-on testing and observation. For this reason, we're not able to offer remote repair or diagnostics. However, we do offer an in-person evaluation and repair service at our local diagnostic center [https://bchtechnologies.com/printer-repair-service]. Please note that due to demand, appointments are scheduled on a first-come, first-served basis, and wait times may be a few weeks. While our service is thorough, we understand it may not be the most affordable solution, which is why we strongly encourage DIY troubleshooting through resources like our YouTube channel [https://youtube.com/@bchtechnologies]. Use the search icon under the "About" tab to find specific topics—we’ve posted hundreds of videos over the past nine years, and many answer questions just like yours.

Thanks again for your message, and for trusting BCH Technologies with your printing setup. We’re always here to help however we can, and we hope you’re back to printing smoothly soon!