First-Time Filling an Epson Printer With an External CIS: Best Priming Method, Safe Startup Steps, and What to Avoid

Question: My Epson is almost ready-what's the best way to fill the ink system for the first time with an external CIS? Should I fill using the CIS, or prime first with a syringe?

My Epson printer is almost ready to go. Can you tell me the best way to fill it for the first time? I'm using an external CIS (not yours because it wasn't available), but I followed your video series and built the setup using your parts. I couldn't find videos specifically about the filling process. Do I fill through the CIS only, or should I prime first using a syringe?

Answer: 

Because you're using an external CIS that isn't ours, I can't safely tell you an exact "do this, then this" procedure for your specific brand's routing and valves. Different CIS systems vary a lot (vent design, check valves, dampers, line diameter, and whether they're intended for gravity feed or mild negative pressure). That said, I can explain the principles that make a first fill successful and what most experienced technicians try to achieve.

The goal of a first fill (no matter what CIS brand)

A good first fill does three things:

1. Gets ink into the lines and dampers without trapping air

2. Establishes stable ink flow at the printhead (not too much pressure, not too little)

3. Avoids flooding the head or starving it while it primes

Most first-fill failures come from either:

• leaving too much air in the line/damper, or

• over-pressurizing the system and flooding the cap station/head area.

CIS filling vs syringe priming: which is "best" for a first-time fill?

Option 1: Filling only through the CIS (works, but can be slow and air-prone)

If you only fill via CIS tanks and rely on gravity and clean cycles:

• it can work,

• but it often takes longer,

• and you can end up with air pockets in the line or damper that don't clear easily.

This is especially true if:

• the ink line path rises and dips,

• the dampers start completely dry,

• or the system has any check valves that restrict flow.

Option 2: Priming with a syringe (often the cleanest way to eliminate air-if done gently)

A syringe prime is commonly used because it:

• pulls ink through the line on purpose,

• removes air faster,

• and lets you confirm that ink actually reaches the damper/head side.

However, it has to be done carefully, because too much suction or pressure can:

• damage dampers,

• pull air leaks through a weak seal,

• or stress the printhead if done aggressively.

In principle:
For many first-time fills, the most reliable approach is to fill the CIS tanks, then prime the ink lines/dampers gently so the system starts with ink near the head instead of mostly air.

The safest "first-fill" concepts to follow (regardless of CIS brand)

1) Set the CIS tank height correctly

One of the biggest causes of problems is incorrect tank height relative to the printhead.

• Too high → excess positive pressure → dripping, flooding, messy cap station

• Too low → starvation, missing colors, hard-to-prime

Most CIS setups are designed to run with tanks roughly level with the printhead (not far above it). Small height changes can matter.

2) Venting matters (especially during first fill)

Many CIS tanks have:

• a fill port (sealed most of the time),

• and an air vent (opened during printing).

If venting is wrong:

• you can create a vacuum lock (no ink flow),

• or create uncontrolled flow (leaks).

3) Aim for "ink at the damper" before you do heavy cleanings

A common mistake is running repeated clean cycles while the dampers are still mostly air. That:

• wastes ink,

• heats the system,

• and can still fail to pull ink if air is trapped.

4) Use gentle priming-avoid forcing ink into the head

Whether you prime from a line, damper outlet, or waste line, the key is gentle movement:

• slow pulls,

• short holds,

• and watching for stable ink (not foamy ink).

Foam is a sign of air ingestion or turbulence-both are enemies of a smooth first fill.

5) After ink is present, let the printer rest between cleanings

Back-to-back cleanings can:

• overheat parts,

• saturate the cap station,

• and create inconsistent results.

Spacing cleaning cycles helps the system stabilize.

What to avoid during a first fill

These are common "first fill" mistakes that create bigger problems:

• Running too many clean cycles immediately (especially if the dampers are still dry)

• Using strong suction or pressure on a syringe (can collapse dampers or introduce leaks)

• Incorrect vent position (no vent = no flow; wrong venting = floods)

• Tanks set too high (constant dripping/flooding)

• Ignoring tiny leaks at fittings-tiny leaks often pull air in even if they don't leak ink out

Error codes mentioned

You didn't mention any specific printer error code numbers in your question-this is mainly a startup/priming workflow question. If you see any on-screen messages during first fill (like "ink not recognized," "cartridge error," or maintenance-related warnings), those would be important to reference exactly as displayed.

Addressing printer issues can be a complicated affair due to the hands-on nature of the problems, especially with custom CIS builds where small differences in routing, tank height, seals, and venting can change the results. So, we're not able to provide remote troubleshooting, suggestions, or support for printer repairs. We offer an in-person evaluation and repair service via our local diagnostic facility, Printer Repair Service (https://bchtechnologies.com/printer-repair-service). Given the high demand, we operate on a first-come, first-served basis, so it might take a few weeks before we can schedule a time for you to drop it off. Our services are structured to repair either a whole printer or specific parts, with clear instructions on how to proceed. However, we acknowledge that our rates aren't the most economical. Thus, we highly recommend that you resort to self-help via online research. You can start by checking out YouTube or visiting our YouTube channel's homepage, BCH Technologies on YouTube (https://youtube.com/@bchtechnologies). Look for specific videos using the search icon next to "About" on the right-hand side of the menu bar. I receive dozens of queries every day asking about videos for specific topics. Having created videos over the past nine years, it's challenging to remember every single one. Therefore, using YouTube's search function would be most efficient. Plus, YouTube might suggest relevant videos from other channels that could assist you.

Thank you again for reaching out, and congratulations on getting your Epson almost ready. First-time filling is one of the most delicate steps, so taking it slowly and focusing on eliminating air and avoiding pressure spikes will give you the best chance of a clean, stable startup.