Most cartridge problems we hear about are not defects. They come from one skipped step during filling. Here is the method we recommend for every PepPen, and why each step matters.
What you need
- A 3 mL glass cartridge
- One vent needle (included in every PepPens kit)
- One pen needle
- Your PepPen
That’s it. No special tools or equipment.
Step 1: Put the vent needle in first
Insert a vent needle through the rubber seal at the top of the cartridge before you add anything. This gives air a way out.
Why it matters: a sealed cartridge has nowhere for air to go. If you add solution without a vent, pressure builds inside and pushes the stopper straight out the bottom. Your solution goes with it. This is the number one reason people think a cartridge “leaked.”
Step 2: Add your solution alongside the vent needle
With the vent needle still in place, add your solution through the seal next to it. Fill no more than 3 mL. Then remove the vent needle.
Step 3: Load the cartridge into your pen
Place the filled cartridge into the cartridge holder and reassemble the pen. On the V1 and V2 Pro, the cartridge twists in and locks. On the V2 and V3, it drops into the open end of the holder.
Step 4: Clear the air before first use
Attach your first pen needle. Dial back about 0.10 to 0.20 mL, point the pen up, and press until the air is out and liquid appears at the tip. Use smaller increments near the end so you don’t waste solution.
Why it matters: trapped air compresses instead of moving liquid. That means the pen keeps dripping after you stop pressing, and you won’t get the full amount you dialed. Ten seconds here fixes it.
Troubleshooting
Liquid leaking from the bottom of the cartridge? The stopper was pushed out by pressure, almost always because the vent needle was missing or removed too early. Use a fresh cartridge and follow Step 1.
Pen keeps dripping after you press? There’s still air in the cartridge. Repeat Step 4.
Stopper looks crooked? Make sure it is fully seated before filling. A stopper that isn’t seated can let liquid past it.
Watch it done
Our short videos walk through each step: Components of the V2 Pen, Filling Your Cartridge, and Preparing Your Pen. You’ll find them on our FAQ page.
Need cartridges or vent needles? Shop 3 mL Glass Cartridges and the Starter Kit. For a printable walkthrough, see our Quick Start Guide.
All PepPens products are sold for research use only.
