Wearable pumps are wonderfully freeing right up until a part wears out and you are standing in the kitchen wondering why your output dropped by half. Willow pumps rely on a handful of small silicone and plastic pieces that quietly do all the heavy lifting, and knowing what they are (and when to swap them) makes the difference between a pump that performs and one that frustrates you. Here is a practical guide to Willow accessories, sizing, and upkeep.
The 90-Day Rule for Willow Parts
Willow recommends replacing the working parts of your pump roughly every 90 days, or sooner if you notice discomfort, reduced output, or visible wear. It is a simple rhythm to remember: once a season, refresh your parts.
- Flextubes (Willow 360): every 90 days, since these carry milk from breast to bag or container
- Diaphragms and valves (Willow Go): every 90 days, as they create and hold the suction
- Milk containers: every 90 days, or sooner if you see cracks or clouding
- Flanges and sizing inserts: replace when worn, and re-check your size as your body changes
- Chargers and cases: replace only when damaged
You can find replacement parts for both Willow models in the Storkpump Willow accessories collection.
Willow Go and Willow 360 Parts Are Not Interchangeable
This trips up a lot of moms, so it is worth saying plainly before you order anything. Willow Go and Willow 360 are built on two different systems, and their accessories do not swap. Each pump has its own flanges, its own containers, and its own internal parts designed for that specific fit and function.
The Willow 360 uses patented Flextubes that carry milk into either a spill-proof milk bag or a reusable container, which is what allows it to be worn in any position without leaking. The Willow Go uses a container-and-diaphragm system with a longer flange tunnel, which many moms with elastic nipples find more comfortable.
Before you add anything to your cart, confirm which model you have. If you are still deciding between them, or comparing wearables against traditional pumps, the Storkpump breast pump collection lays out the covered options side by side.
Flanges, Inserts, and Getting Your Fit Right
Fit matters more with a wearable pump than with a traditional one, because the cup sits inside your bra and shifts as you move. Willow flanges come in 21mm, 24mm, and 27mm, and silicone sizing inserts extend the usable range down into the mid teens for moms who measure smaller. That range exists because most moms are not a standard size, and the size that came in your box may not be your size.
Signs your flange is wrong include pinching at the base of the nipple, a white or blanched appearance after pumping, rubbing along the sides of the tunnel, or milk that stops flowing partway through a session. Sizing down with an insert often solves all of it at once. Measure your nipple diameter (not the areola) with the Storkpump Flange Sizing Guide before ordering, and re-measure every few months, since nipple size commonly changes in the first year of pumping.
Containers, Bags, and Backup Sets
Willow reusable containers come in 5 ounce and 7 ounce capacities, so moms with bigger output can go the full session without stopping to empty. Willow 360 users also have the option of spill-proof milk bags that let you pump directly into storage, which cuts out a transfer step and reduces the chance of spilled milk.
A backup set of containers and parts is the single most useful accessory purchase for a wearable pump user. It means you can pump again before the first set has finished drying, which matters enormously if you pump at work or overnight. Nothing derails a schedule faster than clean parts that are still wet at 3 a.m., and staying on schedule is what protects your supply.
Why Keeping Up With Parts Protects Your Supply
Your body makes milk in response to how completely and how frequently your breasts are drained. A worn diaphragm or a stretched Flextube quietly weakens that signal, so sessions take longer and empty less, and over weeks that can nudge your supply downward. Fresh parts are one of the cheapest, most effective forms of supply insurance there is.
Clean, intact parts also keep milk safe, which the CDC emphasizes as especially important for newborns, premature babies, and babies with weakened immune systems. Helping moms stay ahead of that maintenance is part of why we make accessories easy to find and easy to reorder at Storkpump.
Frequently Asked Questions About Willow Accessories
How often should I replace my Willow pump parts?
Willow recommends about every 90 days for the parts that create suction and carry milk, including Flextubes, diaphragms, valves, and containers. Replace sooner if you notice discomfort, a drop in output, cloudiness, or any visible cracking. Marking your calendar quarterly makes it easy to stay on track.
Can I use Willow Go parts with my Willow 360?
No. The two pumps use entirely separate accessory systems, and parts from one will not fit or function properly on the other. Check your pump model before ordering so you get the right components the first time.
What size Willow flange do I need?
Willow flanges come in 21mm, 24mm, and 27mm, with silicone sizing inserts available for moms who measure smaller. Your size is based on your nipple diameter, not your breast size or your bra size. Measure with the Storkpump sizing guide before your first session, and re-measure periodically as your body changes.
Are Willow accessories covered by insurance?
Coverage for replacement parts and accessories varies by plan, and many plans allow some resupply on a schedule. Willow pumps themselves are often available as an upgrade item, where insurance covers a base amount and you cover the difference. Browse upgrade-eligible pumps here, or check the Storkpump FAQ for details on how verification works.
How many backup sets should I own?
One spare set is enough for most moms pumping a few times a day, and two is a good idea if you pump at work or exclusively pump. The goal is never having to skip or delay a session because your only set is in the drying rack.
Stock Up Before You Need To
The best time to order replacement parts is a few weeks before the 90-day mark, not the morning your suction disappears. Browse the Willow accessories available through Storkpump to restock flanges, containers, and internal parts. For more on choosing between wearable and traditional pumps, or making the two work together, visit the Storkpump Learning Center.
Sources
- Centers for Disease Control and Prevention. About breastfeeding. https://www.cdc.gov/breastfeeding/php/about/index.html
- Academy of Breastfeeding Medicine Protocol Committee. ABM clinical protocols. https://www.bfmed.org/protocols
- Journal of Human Lactation. https://journals.sagepub.com/home/jhl
- Office on Women's Health, U.S. Department of Health and Human Services. Breastfeeding. https://www.womenshealth.gov/breastfeeding
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