HP 62 CISS Printing Problems: How to Fix Ink Starvation, Pressure Imbalance, and Siphoning

Question

I followed the "Turn Any Printer Into an Ink Tank Printer" process and connected a continuous ink supply system, or CISS, to HP 62 cartridges. However, the printer could not create enough suction to pull ink from the external tanks, so the printed pages were incomplete.

When I disconnected the tubing from the cartridge, the cartridge printed normally again. I tried positioning the external tanks at different heights to balance the pressure, but nothing worked consistently. The printer either produced incomplete prints or ink drained through the printhead and created a mess.

I also sealed the cartridges so they were airtight and could draw only ink rather than air. Was making the cartridges airtight a mistake?

Answer

Based on your description, the problem is most likely related to the pressure balance, ventilation, and ink-flow resistance within the CISS rather than a lack of suction from the printer alone. The fact that the HP 62 cartridge prints normally after you disconnect the tubing is a valuable diagnostic clue. It indicates that the cartridge and printhead can still fire ink, but the external ink system is interfering with the cartridge's normal internal pressure regulation.

Should an HP 62 Cartridge Be Completely Airtight?

Making the cartridge completely airtight can create problems.

An ink cartridge must maintain a controlled pressure balance. It cannot simply be sealed so tightly that no air can enter anywhere. As ink leaves the cartridge during printing, something must compensate for the lost volume. In a standard cartridge, this is usually handled through a carefully designed venting system and an internal sponge or pressure-regulating structure.

When a CISS tube is connected, the external tank and tubing become part of that pressure system. If the cartridge is completely sealed and the CISS cannot supply ink quickly enough, a vacuum develops inside the cartridge. The printer may initially print, but the ink flow will gradually weaken. This can cause:

• Missing lines in the nozzle pattern

• Faded or incomplete prints

• One or more colors dropping out

• Printing that starts normally and then becomes blank

• Temporary recovery after the tubing is disconnected

Therefore, sealing the cartridge against uncontrolled air leaks is important, but sealing it so completely that the system cannot equalize pressure may prevent ink from flowing.

The objective is not to make the entire cartridge absolutely airtight. Instead, the connection between the cartridge and tubing must be sealed against leaks while the CISS tank uses its intended air vent to regulate pressure.

Why Disconnecting the Tube Restores Printing

When you remove the tube, the cartridge returns closer to its original operating condition. The internal sponge can deliver the ink already stored inside the cartridge without having to overcome the resistance created by the tubing and external tank.

This suggests that one or more of the following problems may be occurring:

• The tubing contains air bubbles.

• The tubing is too long, narrow, kinked, or restricted.

• The ink tank vent is closed.

• The cartridge connection is blocked by sealant or adhesive.

• The external tank is positioned too low.

• The external tank is positioned too high and causes siphoning.

• The cartridge's internal sponge is oversaturated or compressed.

• The tubing connection enters an unsuitable part of the cartridge.

• The cartridge cannot regulate pressure properly after modification.

A thermal inkjet cartridge such as the HP 62 is designed primarily to operate as a self-contained cartridge. It was not originally engineered to pull ink continuously through a long tube. Even a small amount of flow resistance can interrupt printing.

Why Raising the Tanks Causes Ink to Drain Through the Printhead

If the external tanks are positioned too high, gravity creates positive pressure. Instead of allowing the cartridge to draw ink only when needed, the elevated tank pushes ink into the cartridge.

Once the internal sponge becomes saturated, the excess ink must escape somewhere. It may leak through the printhead nozzles, pool beneath the cartridge, contaminate the carriage, or drip into the printer.

This is known as siphoning or gravity feeding. Typical signs include:

• Ink dripping from the printhead

• Ink accumulating under the cartridge carriage

• Colors mixing inside the service station

• Heavy smearing on the paper

• Ink continuing to flow while the printer is turned off

• The external tank level falling without printing

Lowering the tank can stop the siphoning, but placing it too low creates excessive negative pressure. The cartridge then struggles to pull ink upward, resulting in ink starvation.

This is why the tank height must be adjusted very carefully. In most CISS installations, the functional ink level inside the external tank should remain approximately level with the printhead or slightly below it. However, the correct position depends on the tank design, tubing length, cartridge structure, and whether the tank includes a pressure-balancing chamber.

The bottom of the tank is not always the correct reference point. The actual ink surface and the tank's pressure chamber determine the effective pressure.

Check the Air Vent on the External Tank

Many CISS tanks have two openings:

• A larger filling port

• A smaller air vent

During operation, the filling port is normally closed, while the smaller vent is opened or fitted with an air filter. If both openings are closed, ink leaving the tank creates a vacuum, and the cartridge eventually stops receiving ink.

If the vent is too large, improperly configured, or connected to the wrong chamber, the tank may deliver too much pressure and cause leaking.

Confirm that:

• The correct air vent is open during printing.

• The filling port is securely closed.

• Any supplied air filter is installed in the vent opening.

• The tank is standing upright.

• The tank chambers are filled according to the manufacturer's instructions.

• Ink has not entered and blocked the air filter.

Some CISS tanks use a smaller pressure-balancing chamber. Tilting the tank or filling the wrong chamber too high can defeat the pressure-control design.

Remove Air From the Tubing Before Testing

Large air gaps in the tubing can interrupt ink delivery. Although a small bubble may not always stop a properly designed system, a long air pocket can compress and expand instead of transmitting ink consistently.

The tubing should be fully primed before the system is expected to maintain cartridge ink levels. Priming generally involves drawing ink through the line until the tubing is filled and the major air gaps are removed.

Do not rely on the printer to pull a completely empty ink line from the external tank. HP 62 cartridges and their internal sponges may not generate enough stable negative pressure to prime a long tube.

You can review our article about preparing continuous ink supply tanks here: How to Prime CIS Tanks [https://bchtechnologies.com/blogs/news/how-to-prime-cis-tanks].

When priming, avoid pulling so aggressively that the cartridge sponge becomes flooded. The goal is to bring ink to the cartridge connection without forcing excessive ink through the printhead.

Inspect the Tubing and Cartridge Fitting

The tubing route can also create resistance. Check the entire ink path for:

• Sharp bends

• Pinched sections

• Tubing trapped beneath the printer cover

• Loose fittings that draw air

• Dried ink inside the connector

• Sealant obstructing the drilled opening

• Tubing that is too rigid or too narrow

• A connector pressed too deeply into the cartridge sponge

If a fitting is inserted too far, it may compress the sponge and restrict ink movement. If it is not inserted far enough, it may draw air around the fitting.

The seal should prevent air from leaking around the tube, but the ink passage itself must remain fully open.

The HP 62 Internal Sponge Must Remain Balanced

HP 62 cartridges contain absorbent material that stores ink and controls its delivery to the printhead. A CISS must keep that sponge moist without flooding it.

If the sponge becomes too dry, the cartridge cannot transfer ink to the nozzles reliably. If it becomes oversaturated, ink can leak from the printhead.

This creates a narrow operating range:

• Too little pressure causes ink starvation.

• Too much pressure causes flooding.

• A blocked vent creates a vacuum.

• An open leak allows air into the cartridge.

• Excessive tank height creates siphoning.

• Insufficient tank height increases pulling resistance.

Because of this, sponge-based cartridges can be more difficult to convert successfully than cartridges designed with a dedicated ink inlet and pressure regulator.

Test One Cartridge at a Time

If the CISS contains multiple colors, test each modified cartridge individually when possible. One leaking line or poorly sealed fitting can affect the behavior of the entire tubing arrangement.

Begin with the following checks:

1. Confirm that the cartridge prints correctly without the CISS tubing.

2. Prime the tubing until it contains ink without large air pockets.

3. Position the external tank approximately level with or slightly below the cartridge printhead.

4. Open the correct tank vent and close the filling port.

5. Reconnect the tubing without compressing the cartridge sponge.

6. Print a nozzle test or a small color pattern.

7. Watch the tubing for bubbles moving toward the cartridge.

8. Inspect the printhead for dripping after printing stops.

If the cartridge prints properly for a short period and then fades, the system is probably developing excessive negative pressure or drawing air.

If ink begins dripping immediately, the tank is probably too high, the cartridge is oversaturated, or the system lacks adequate pressure regulation.

Avoid Repeated Cleaning Cycles

Repeated printhead-cleaning cycles may temporarily pull more ink into the cartridge, but they can also make the situation worse. Cleaning cycles consume a significant amount of ink and may rapidly flood the cartridge if the tank is already applying positive pressure.

Use a nozzle test or a small print pattern between adjustments. This provides a clearer indication of whether the pressure balance has improved without unnecessarily filling the waste-ink system.

A Damper or Flow-Control Device May Be Necessary

Some CISS conversions require a damper, check valve, or other pressure-control component between the external tank and cartridge. These parts can reduce sudden pressure changes and help prevent ink from flowing freely through the printhead.

However, adding a restriction can also make ink starvation worse if the cartridge already struggles to draw ink. Therefore, any damper must be compatible with the ink viscosity, tube diameter, and cartridge design.

A simple external tank connected directly to an HP 62 cartridge may not remain stable under all conditions. The system can work temporarily but become inconsistent as the tank level changes, the room temperature changes, or air enters the tubing.

Environmental Conditions Can Affect the System

Temperature and elevation can influence a CISS because they change air pressure and ink viscosity. Warm ink flows more easily and may increase leaking. Cold ink moves more slowly and may contribute to starvation.

Direct sunlight or heat near the external tanks can cause the air inside the tank to expand, pushing ink toward the cartridge. Keep the tanks at a stable room temperature and avoid placing them above a heater, in direct sunlight, or beside warm printer electronics.

Most Likely Explanation in This Case

Your description suggests that the cartridge itself still works, but the CISS is not maintaining neutral pressure.

When the tank is low, the cartridge cannot overcome the combined resistance of the tubing, fitting, and ink column. When you raise the tank, gravity overcomes that resistance but creates too much positive pressure, causing ink to drain through the printhead.

Making the cartridge completely airtight may intensify the starvation problem because the cartridge cannot compensate for the ink leaving its internal sponge. At the same time, simply opening the cartridge to the atmosphere would allow air to enter and could also disrupt the ink supply.

The cartridge-to-tube connection should be airtight, but the entire ink system still needs controlled ventilation through the external tank's designed vent. The tubing must be primed, the cartridge sponge must not be flooded, and the external tank must be positioned within a narrow height range.

Unfortunately, some HP 62 cartridges may remain unreliable when converted to a CISS because their original pressure-control system was not designed for continuous external feeding. In those cases, a refillable cartridge with an engineered ink inlet and pressure-control system may be more dependable than modifying the original cartridge.

Addressing printer issues can be complicated because many problems require direct inspection, testing, and hands-on adjustments. For this reason, we cannot provide individualized remote troubleshooting or ongoing repair support.

We do offer in-person printer evaluation and repair through our local diagnostic and printer repair facility [https://bchtechnologies.com/printer-repair-service]. Due to high demand, service is provided on a first-come, first-served basis, and it may take several weeks before an appointment or drop-off opening becomes available. Our service options cover complete printers as well as certain individual parts, with instructions explaining how to proceed. However, we recognize that professional repair may not be the most economical choice for every situation.

Therefore, we strongly encourage self-guided research whenever practical. You can begin with YouTube or visit the BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies]. To locate videos about a specific printer, cartridge, conversion, or error, use the search icon beside the "About" section on the channel menu.

We receive dozens of questions each day asking whether we have a video about a particular subject. Because we have published repair and technical videos for more than nine years, it is difficult to remember every video individually. Using YouTube's channel search feature is usually the fastest way to locate relevant information. YouTube may also recommend useful videos from other creators that address similar CISS pressure and ink-flow problems.

Thank you again for contacting BCH Technologies and for sharing such a detailed description of your testing. Your observations about the cartridge printing normally after the tube was removed were especially helpful in identifying the likely pressure-balance problem. We sincerely appreciate your support and hope this information gives you a clearer direction for evaluating the CISS installation.