Why Canon Spongeless Refillable Cartridges Do Not Keep Leaking After Pressure Cleaning

Question

I watched your video about making Canon spongeless refillable cartridges, including models such as PG-240, CL-241, PG-245, and CL-246. When you apply pressure into the cartridge to unclog the printhead, why does the ink not continue pushing out afterward?

I tried something similar with an old Canon CL-561 cartridge. After removing the original cover, I poured DI water into the three color tanks and left it overnight. The water leaked out, so I am wondering why the ink would not leak out the same way when using the refillable setup.

Answer

When pressure is applied to a cartridge to unclog the printhead, that pressure is only temporary. It forces ink or cleaning fluid through the tiny nozzle openings to help push out dried ink, air pockets, or debris. Once you stop applying pressure, the force that was pushing the liquid forward is removed. At that point, several things help stop the ink from continuing to flow: the internal pressure balance, nozzle resistance, surface tension, ink viscosity, and, most importantly in the BCH spongeless design, the regulated cover system.

The BCH cover is not simply a flat lid or an open cap that holds ink inside the cartridge. It is designed with pressure control in mind. The cover helps regulate the air exchange inside the cartridge so the ink can feed when the printhead needs it, but it does not allow the cartridge to behave like an open container that freely drains. In other words, the cartridge needs a controlled balance between air entering and ink leaving. If too much air enters too freely, the cartridge can drip or siphon. If not enough air enters, the cartridge can starve and stop feeding. The regulated cover helps maintain that balance.

This is why the cartridge does not keep pushing ink out after you use pressure to unclog the head. During the pressure step, you are overriding the cartridge's normal feeding behavior by manually forcing liquid through the nozzles. Once that pressure is gone, the system returns to its balanced state. The tiny printhead nozzles are not large open holes; they are extremely small openings. Ink does not simply pour through them unless there is enough pressure, gravity imbalance, siphoning, or air exchange to keep the flow going.

Your experiment with DI water also makes sense. DI water is much thinner than ink. It has lower viscosity, so it can pass through small openings and gaps much more easily. Ink is thicker and is formulated to behave differently inside the cartridge and printhead. It also has different surface tension properties, which help it stay controlled inside the ink chamber and nozzle plate.

Also, when you removed the original cover from the Canon CL-561 cartridge and poured DI water directly into the three tanks, the cartridge was no longer in its normal sealed or pressure-balanced condition. At that point, it was closer to an open container. Without the proper sealed cover and pressure regulation, the water could leak out overnight through the printhead, seams, vents, or any path where gravity and air exchange allowed it to drain. That does not accurately represent how the cartridge behaves when the BCH regulated cover is properly installed and sealed.

The key point is that a spongeless refillable cartridge must not be treated like an open ink tank. It still needs controlled pressure. In sponge-based cartridges, the sponge helps hold the ink in place and slows the movement of liquid. In a spongeless cartridge, the design must replace that sponge function with proper chamber structure, sealing, and air regulation. If the cover is not sealed correctly, if the venting is uncontrolled, or if the cartridge has a damaged printhead or gasket area, then leaking can still happen. But when the BCH cover is installed correctly, it helps prevent uncontrolled draining while still allowing ink to feed during printing.

If a cartridge leaks after conversion, I would check the following areas:

First, make sure the BCH cover is seated evenly and sealed correctly. Any small gap can allow air to enter too freely, which can create a siphon effect and cause leaking.

Second, check whether the printhead nozzle area is damaged. If the nozzle plate or internal filter area has been physically damaged, the cartridge may not hold ink normally.

Third, avoid testing with plain DI water and assuming the result will match ink behavior. DI water is useful for cleaning and flushing, but because it is thinner than ink, it is more likely to leak through places where ink may not leak as quickly.

Fourth, make sure the cartridge is not overfilled. Too much ink can reduce the internal air space needed for pressure balance. A cartridge needs both ink and controlled air space to work correctly.

Fifth, make sure the cartridge is stored in the correct position. If it is left with the printhead facing downward for a long period, especially if it has been overfilled or recently pressurized, it may drip.

Sixth, after applying pressure to unclog the printhead, stop and let the cartridge stabilize. Wipe the printhead area, place it on a non-absorbent surface briefly, and check whether it continues to drip. A few drops immediately after pressure cleaning can be normal because liquid remains on or near the nozzle plate. Continuous dripping is not normal and usually points to an air leak, poor seal, overfilling, or damage.

So, in short, the reason the ink does not keep leaking with the BCH cover is that the cover is designed to regulate pressure. The pressure cleaning step temporarily forces liquid through the printhead, but once the pressure is removed, the regulator, ink viscosity, surface tension, and nozzle resistance work together to stop continuous flow. In your DI water test, the cartridge was open, unregulated, and filled with a much thinner liquid, so leaking overnight would be expected.

Addressing printer issues can be a complicated affair because many of these problems require hands-on inspection and testing. Because of that, we are not able to provide remote troubleshooting, suggestions, or repair support for every printer or cartridge issue. However, we do offer in-person evaluation and repair through our local diagnostic facility, which you can find here: BCH Technologies Printer Repair Service [https://bchtechnologies.com/printer-repair-service]. Due to high demand, we operate on a first-come, first-served basis, so it may take a few weeks before your printer can be dropped off or evaluated. Our services are structured to repair either a complete printer or specific parts, with instructions provided on how to proceed. We also understand that our repair rates may not be the most economical option for every situation, so we strongly encourage self-help through online research whenever possible. A good starting point is YouTube, especially our channel homepage at BCH Technologies on YouTube [https://youtube.com/@bchtechnologies]. You can use the search icon next to "About" on the right-hand side of the channel menu bar to look for specific repair topics. I receive dozens of questions every day asking for videos on specific subjects, and after creating videos for the past nine years, it is difficult to remember every single one. YouTube's search function is usually the fastest way to locate the most relevant video, and it may also recommend helpful videos from other channels.

Thanks again for your thoughtful question and for supporting our videos. Questions like this are very helpful because they allow us to explain not only what to do, but why the cartridge behaves the way it does.