Yes HP 56 ink cartridges can be refilled. Let me remind you though it is a long process.
There are many companies online that offer refillable ink cartridges. office supply stores such as Staples and Office Max also offer refillable ink cartridges.
I really don't like using refillable ink cartridges as they have a tendency to damage your printer. From what I've seen online HP and Epson both offer refillable ink jet cartridges.
One study done for Hewlett-Packard found that refillable printer cartridges produced fewer printed pages and were more likely to malfunction than HP cartridges. The study was not independent, and many people still use refillable printer ink cartridges. Their reliability may be enough for you if your printing needs are basic, and reliability would depend on the brand of refillable cartridge, so you might try them and see if they are reliable enough for your needs.
There are variations of hp printer ink cartridges. There are 688 hp printer ink cartridges available on the HP website. For more information go to http://welcome.hp.com/country/us/en/welcome.html.
One can go to the official HP website for HP 3310 ink cartridges. In addition, one can go to eBay or Amazon for HP 3310 ink cartridges online for one's printer.
The HP PhotoSmart 7150 printer uses the following 3 ink cartridges: #56 Black, aka C6657AN #57, Tri color, aka C6657AN #58, Photo, aka C6658AN
Generic HP ink cartridges are cheaper than HP brand cartridges. They are about $50 cheaper, brand name items are normally more expensive. HP brand cartridges normally cost about $100.
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HP Photosmart printers use the line of HP 564 ink. Any of the Photosmart printers can be fitted with a HP 564 Black Ink Cartridge, HP 564 Photo Ink Cartridge, HP 564 Cyan Ink Cartridge, HP 564 Magenta Ink Cartridge, HP 564 Yellow Ink Cartridge, HP 564XL Black Ink Cartridge, HP 564XL Photo Ink Cartridge, HP 564XL Cyan Ink Cartridge, HP 564XL Magenta Ink Cartridge, or a HP 564XL Yellow Ink Cartridge.
One can purchase HP 15 ink cartridges at a website called Amazon. Another store that one can purchase HP 15 ink at is Staples. Best Buy is also a good place to find these ink cartridges.
Usually the best ink cartridge to use with an HP printer is an actual HP ink cartridge. However, many office supply stores and online retailers will offer a variety of re-manufactured and/ or refillable ink cartridges compatible with most brands of printers including HP.
One can purchase HP ink No 15 cartridges by going to stationery stores. Ink from HP can also be bought from HP sites. Some online stores such as Amazon and eBay sell this ink as well.