Pipette Filler, 3 way

Quick Answer: The Pipette Filler, 3 way is a rubber suction bulb with three built-in valves, usually marked A, S and E, that fits onto the top of a glass pipette. A 3 way pipette filler draws liquid up and lets it out under finger control, so pipetting never needs the mouth.

The Three Valves and What Each Does

Each valve is a small ball or seat inside the rubber that opens when the bulb is pinched at that point. Valve A, at the top, lets air out: squeeze A and the bulb together to empty the bulb. Valve S, just above the pipette stem, is for suction: pinch it and liquid rises into the pipette as the bulb re-expands. Valve E, on the short side arm, empties: pinch it and air enters, letting the liquid run down to the mark or out into the receiving flask.

This fine control is what distinguishes it from a plain pipette bulb, which gives suction but has no way to hold or release the liquid gradually. Compared with a thumbwheel pipette pump, the three-valve filler fits a wider range of pipette sizes with one device, though the fit is less positive on very small pipettes. It suits the graduated and bulb (volumetric) pipettes used in titration practicals.

The one rule that protects the filler is to keep liquid out of the bulb. Drawing liquid above the top of the pipette floods the valves, and acids or alkalis inside the rubber shorten its life and can spray out on the next squeeze.

Where It Is Used

• Measuring aliquots with a bulb pipette in acid-base and redox titrations
• Dispensing graduated volumes of reagent in school and college practicals
• Pipetting corrosive, toxic or strong-smelling liquids that must never be mouth-pipetted
• Preparing dilution series in biology and food-testing practicals

Specifications

Care & Handling

• Insert the pipette only a short way into the lower stem, twisting gently; pushing it deep can crack the glass or split the rubber.
• Stop suction before the liquid reaches the top of the pipette.
• If liquid does enter the bulb, flush it with water through the valves and let it dry fully before reuse.
• Store fillers without pipettes attached, away from sunlight and solvent fumes.

Why Choose LabEquip

Three-valve fillers are bought in class sets by schools and colleges enforcing a no-mouth-pipetting rule, usually one per bench or titration station. LabEquip includes them in General Lab Products; tell us the pipette sizes you use via the contact page.

Frequently Asked Questions

What do the letters A, S and E stand for?

A is for air, used to expel air from the bulb before suction. S is for suction, used to draw liquid into the pipette. E is for empty, used to let the liquid flow out.

How do I fill a pipette with a 3 way filler?

Fit the filler to the pipette, press A and squeeze the bulb flat, then release A. Dip the pipette tip below the liquid and press S gently until the liquid rises just above the mark. Adjust down to the mark with E, then release the rest into the flask with E.

Why does the liquid level drift down after filling?

Usually the pipette is loose in the stem, so air leaks in, or a valve is worn and no longer seals. Push the pipette in slightly further with a twist, and replace the filler if a valve keeps leaking.

Can it be used with plastic pipettes?

Yes, as long as the pipette top is a suitable diameter to seal in the lower stem. Very narrow or very wide pipettes may need a different filler or an adapter.

What happens if liquid is sucked into the bulb?

The valves can stick and the rubber is exposed to the reagent. Rinse by drawing water up and expelling it through the valves several times, then let the filler dry before its next use. Corrosive liquids can shorten its life.

Is a 3 way filler more accurate than a pipette pump?

Accuracy comes from the pipette and from reading the meniscus correctly. The filler’s job is to give steady control; a thumbwheel pump offers finer adjustment, while a three-valve bulb covers more pipette sizes.

Last Updated: September 2026