Anatomy of an HP Twin Chamber Cartridge

Today we’ll be going over the first part of a series I did a while ago about how to refill an HP Twin Chamber cartridge. A Twin Chamber cartridge is divided into two chambers, as the name might suggest. The rear chamber is designed to serve as an ink reservoir. The front section is full of sponges, which regulate the amount of ink flowing to the outlet on the bottom of the cartridge. A plastic wall separates these two chambers. XL cartridges will have a hole at the bottom of that wall allowing ink to flow from the reservoir to the sponges as needed.

Non-XL cartridges still have the reservoir but no hole in the wall, so the rear chamber is basically useless. HP intends for the rear chamber on a regular or startup cartridge to never be used. Still, if you can somehow form a hole in that wall’s bottom, you can convert any cartridge into an XL cartridge.

If you look at the top of the cartridge, you’ll notice a T-shaped air intake that leads to a long, winding air channel. This air channel then connects to an air hole, allowing the cartridge to “breathe” when used.

On top of the rear chamber is a refill hole. HP uses this hole for XL cartridges to inject ink into the cartridge, then seals it with a plastic ball. Despite not intending the rear chamber to be used on a startup or regular cartridge, they still have this refill hole. That being said, we only tend to refill the front chamber on non-XL cartridges.