What Ink Does the Epson EcoTank ET-3950 Use?

Quick answer: the Epson EcoTank ET-3950 uses Epson 502 ink bottles — not cartridges. Four bottles, one per tank, and there is no XL tier, because a bottle simply fills a tank rather than being a fixed-capacity cartridge.

The wrong answer people land on is Epson 522. That family belongs to the ET-2800, ET-4800, ET-4810 and ET-2903. The bottles are keyed differently under Epson's EcoFit system, so a 522 will not fit an ET-3950 — and while you are checking, note that the two families also use different maintenance boxes. The ET-3950 takes a T04D100; the 522 machines take a C9344.

Epson EcoTank ET-3950 ink at a glance

Those figures come from Epson's own specification sheet for the ET-3950. You will see lower numbers quoted elsewhere — 7,500 black and 6,000 color — because those are the older published figures for the same 502 bottles, and they still circulate on retailer listings. The 8,500 and 6,500 numbers are the ones Epson publishes for this printer.

A separate figure not to confuse with either: Epson says the bottles included in the box deliver up to 6,600 black and 5,500 color. That is lower because the initial fill charges the ink delivery system. Both are Epson's numbers; they measure different things.

What it actually costs to run

Castle Ink's compatible 502 four-pack is $38.95. Against Epson's 8,500-page rating for the black bottle, that works out at roughly 0.3 cents per black page once you apportion the black bottle's share of the pack. A cartridge-based all-in-one in the same class runs 10 to 15 cents.

In plain terms: 8,500 pages of black text costs about $15 in ink here. The same 8,500 pages on an entry-level cartridge printer runs well past $850. That single comparison is the entire argument for a tank printer, and you can run it against your own volumes with the ink cost calculator.

Castle Ink recommendation

Castle Ink stocks a compatible Epson 502 four-pack (BCMY) for $38.95, guaranteed for a year. One pack fills all four tanks.

Two things to watch when shopping elsewhere. Sublimation bottles are routinely titled "502 / 512 / 522" together — they fit the ports but are a heat-transfer ink chemistry that does not belong in a document printer. And plenty of sellers title 502 items as "ink cartridge". This printer takes bottles; there is no 502 cartridge to find.

How to refill the tanks properly

1. Wait until the printer says a tank is low. Do not top up early — once ink is mixed you cannot judge the level.
2. Open the tank cover and unlock the cap for the color you are filling.
3. Hold the bottle upright in the port. Epson's design meters the flow and stops when full, so there is no need to squeeze.
4. Fill all the way to the top line, then close the cap firmly and complete the level reset on the LCD.

Never let a tank run below its lower line — Epson warns that printing below it can damage the printer — and never mix colors between ports.

About the Epson EcoTank ET-3950

Print, scan and copy — no fax — with automatic two-sided printing, a 30-sheet ADF and a 250-sheet paper cassette. Rated at 18 ISO ppm black and 9 ppm color, dropping to about 7 and 5 with duplex enabled.

The display is a 2.4-inch color LCD, not a touchscreen. Connectivity is better than the cheaper EcoTanks: Wi-Fi 5 on both 2.4 and 5 GHz, Wi-Fi Direct, plus 10/100 Ethernet and USB.

One point of precision on the ADF: Epson specifies it as "1-sided to 2-sided scanning", which means it feeds single-sided originals to produce two-sided output. It is not a duplex-scanning ADF, and some listings imply otherwise.

The maintenance box is a T04D100, around $11, and Epson explicitly labels it user-replaceable — a real advantage over the cheaper ET-2800 class, where the waste pads are not owner-serviceable.

The ET-3930 and ET-3940 are its direct siblings on the same ink; the ET-3930 has no ADF.

Common problems on this model

Faint or missing colors after the printer sits idle

The dominant EcoTank complaint, and it is dried nozzles rather than an ink problem. Epson's escalation, in order: Nozzle Check, then Print Head Cleaning, then Power Cleaning only if gaps remain — Power Cleaning uses a great deal of ink and should be a last resort. Finish with a print head alignment. Printing one color page a fortnight prevents most of it; see whether ink dries out.

Blank or very faint pages

Check the tanks visually through the window — the printer estimates levels by counting usage rather than sensing them, so the display can be wrong after a refill. Then run a nozzle check.

Will not join Wi-Fi

Print the Network Connection Report from the panel. Epson gives numbered error codes, E-1 through E-13, each with its own remedy — that is far more useful than generic advice. Our printer Wi-Fi setup guide covers the Epson path.

Paper feed problems

Usually roller cleaning, stack height or guide alignment. See our paper jam guide.

FAQ

What ink does the Epson EcoTank ET-3950 use?

Epson 502 ink bottles in black, cyan, magenta and yellow.

Does the ET-3950 use Epson 522?

No. 522 fits the ET-2800, ET-4800, ET-4810 and ET-2903. The bottles are keyed differently and will not fit.

Is there an Epson 502XL?

No. There is one bottle size. Epson markets 502 as ultra-high capacity, which is branding on the base product rather than a tier above it.

Which other printers use Epson 502?

A long list, including the ET-3930, ET-3940, ET-3943, ET-3958, ET-2850, ET-2980, ET-3760, ET-3843, ET-3850, ET-4850, ET-4950 and ET-15000.

Does the ET-3950 fax?

No. It prints, scans and copies. Fax in this generation sits on the ET-4850 and ET-4950.

Can I use compatible 502 ink without voiding the warranty?

Yes. US law prevents a manufacturer voiding your warranty purely for using third-party supplies — see the legal answer.

Shop Epson 502 ink now

Grab the 502 four-pack. Different printer? Find yours on our Find Ink by Printer page, or see how your model ranks on running cost in the monthly CastleScore rankings.