Question: Is Replacing Duckbill Valves Just a Gimmick?
Is Replacing Duckbill Valves Just a Gimmick?
I’ve been exclusively pumping for 6.5 months and have recently watched a video that showed that you need to replace your duckbill valves. The video showed you can test if the old parts are bad by putting water in them and setting if water drips out. I got some new basics though and the new ones leak water. Are the parts just bad or is replacing the duckbills just a gimmick?
UPDATE I just tried the suction trick where you suck on the valve to see if any air comes through. It doesn’t come through with both the new and old ones. I’m feeling very confused.
I also run them through the dishwasher every night.
I just switched out my old parts for new valves and suction circles. I’m getting less milk now. I don’t understand what I’m doing wrong, and now I threw out the old parts.
DuckBillValveFactory.com Answer:
Valve expert from DuckbillValveFactory here. Let me cut straight to the chase: No, replacing duckbill valves is NOT a gimmick — but the way people test them and interpret the results often is. Your confusion is completely understandable, and your experience (new valves leak water, pass the suction test, yet give you less milk) actually reveals several important engineering principles that most online advice gets wrong.
Why your water test is misleading
A duckbill valve is a dynamic check valve, not a static seal. Its job is to:
Open under forward pressure (pump suction → milk flows out)
Close under reverse pressure (pump releases → no backflow)
When you pour water into the top of a duckbill valve (from the open end opposite the bill), you’re testing something the valve was never designed to do. Water dripping through from that direction can happen for several reasons that have nothing to do with wear:
Surface tension & wetting – A brand‑new, perfectly functional duckbill may let water drip if the silicone is clean and the lips aren’t fully wetted. Once milk fat coats the inside, surface tension actually helps the seal.
Orientation – Duckbills are designed to seal against pressure coming from the rounded base side. Pouring water into the bill side is essentially backflow direction – a good valve should leak a little there (it’s not a perfect check valve in reverse at low pressure).
Manufacturing flash – New valves sometimes have microscopic molding residue that prevents perfect lip contact until they’ve been used a few times.
The correct test for a worn duckbill is not water dripping – it’s visual inspection and cracking pressure feel. Hold the valve up to light. Can you see a gap between the lips when it’s relaxed? If yes, replace. Pinch the lips together gently – they should spring back. If they stay deformed or feel gummy, replace.
Why your suction test (sucking air) is better, but still not perfect
Sucking on the valve to see if air comes through tests whether the lips seal under negative pressure (vacuum). Both your old and new valves passed – that means both seal well when you apply suction. This is good news. It suggests your old valves were not catastrophically failed. But here’s the catch:
A valve can pass the suction test and still hurt your output if its cracking pressure has changed.
Cracking pressure is the minimum vacuum needed to open the lips. Worn valves typically have lower cracking pressure (easier to open). New valves, especially from different brands or batches, often have higher cracking pressure (stiffer). Your pump has a fixed vacuum strength. If the new valves require more vacuum to open than your pump provides at your comfortable setting, they may not open fully or consistently – leading to less milk even though they seal perfectly when closed.
Why you’re getting less milk with new parts – the likely explanation
You switched to new duckbill valves AND new “suction circles” (I assume these are the backflow protector membranes). Two possibilities:
Higher cracking pressure on the new duckbills – This is the most common cause. Old, worn valves become soft and floppy. They open at very low vacuum, allowing milk to flow easily. New, stiff valves may need a stronger vacuum. Solution: Try increasing your pump’s vacuum level slightly for a few sessions. If output improves, that confirms the issue. Over 1–2 weeks of use, silicone softens slightly (mechanical break‑in), and output often returns to normal.
Incompatibility or defect – Not all duckbill valves are equal. If you bought off‑brand (e.g., generic Amazon vs. official Legendairy/Medela/Spectra), the dimensional tolerances may be off. A valve that is 0.5 mm longer or has a thicker lip can drastically change performance. Solution: Compare the new and old side‑by‑side. Pinch each – does the new one feel noticeably stiffer? If yes, that’s your answer.
The dishwasher problem
You mentioned running parts through the dishwasher every night. This is significant from a materials engineering standpoint. Commercial dishwasher detergents are highly alkaline (pH 10–12) and combined with high heat (65–75°C / 150–170°F), they accelerate silicone degradation. Over 6.5 months, your old valves likely became softer and more compliant – not necessarily “worn out” in a leaky sense, but chemically softened. That’s why they worked well for you. The new valves, never dishwashed, are at their original stiffness. The dishwasher changed your old valves’ material properties, not just their sealing.
So, is replacement a gimmick?
No – but blindly replacing with any random “compatible” valve and expecting better output is a gimmick. Here’s what actually matters:
Replace when you see visible lip gap, deformation, or tears.
Replace if you notice a sudden unexplained drop in output that doesn’t resolve after checking other variables (flange fit, pump battery, etc.).
Always break in new valves – run them through 2–3 pump sessions (or cycle your pump empty for 5 minutes) before judging performance.
Stick with OEM or proven third‑party brands (Maymom, Nenesupply, Pumpin; Pals) that publish durometer specs.
Stop dishwashing silicone parts daily – hand wash with mild soap and air dry. If you must use a dishwasher, put parts in a closed container or a top‑rack basket away from detergent tablets.
What to do now
You threw out the old parts – that’s unfortunate, but not a disaster. Here’s your recovery plan:
Keep using the new valves for 3–5 more days. Your output may come back up as they break in.
Slightly increase your vacuum level if your pump allows it (e.g., from level 5 to 6 or 7).
If output remains low after a week, buy a small pack of official brand valves (Legendairy, Medela, Spectra – whatever matches your cups). Test one of those against your current new ones. If the official ones work better, your Amazon generics are the problem.
Hand wash from now on – warm water, mild dish soap, soak, rinse, air dry. No dishwasher, no brushes inside the valve.
Bottom line: Your old valves weren’t “bad” – they were softened by dishwashing and pumping. The new ones are stiffer, which temporarily reduced your output. This doesn’t mean replacement is a gimmick; it means you need to match the valve;s mechanical properties to your pump and your body. Give the new ones a few days, adjust your vacuum, and you’ll likely be fine.