Every part of your breast pump that touches breast milk should be sterilized. That includes the flanges (breast shields), valves, valve membranes, connectors, backflow protectors, and milk collection bottles or containers. Parts that never contact milk, like the tubing and the motor unit, do not need sterilizing.
Parts That Need Sterilizing
The simplest rule: if breast milk flows through it or pools in it, sterilize it. For most pumps, that means these components:
- Flanges (breast shields): The cone-shaped cups that fit over your nipple and areola. Milk passes directly through them every session.
- Valves and valve membranes: Small silicone pieces that open and close to create suction. Milk contacts them constantly during pumping.
- Connectors: The pieces that link the flange to the bottle or bag. Milk flows through them on its way to the collection container.
- Backflow protectors: Found in closed-system pumps (like Spectra or Elvie), these sit between the connector and the tubing to prevent milk from reaching the motor. Because they can contact milk or milk vapor, they should be cleaned and sterilized along with everything else.
- Bottles or collection containers: Where expressed milk collects and sits until you transfer or store it.
If your pump came with any additional pieces that sit in the milk pathway, include those too. Your pump’s manual will have an exploded diagram showing exactly which parts disassemble for cleaning.
Parts You Should Never Submerge or Sterilize
The motor unit (the electrical box that holds the motor and batteries) should never go into water, a sterilizer, or a microwave. Wipe it down with a clean paper towel or soft cloth after each use. That’s it.
Tubing does not need cleaning or sterilizing unless breast milk actually gets inside it. In a closed-system pump, the backflow protector prevents that from happening under normal conditions. If you do wash your tubing for any reason, hang it to air dry completely before reattaching it. If you notice small water droplets (condensation) inside the tubing after a session, run the pump for a few minutes with the tubing attached to blow the moisture out.
How Often to Sterilize
The CDC recommends sanitizing all milk-contact parts at least once a day. This daily sterilization is especially important if your baby is younger than 2 months, was born prematurely, or has a weakened immune system due to illness or medical treatment. For older, healthy babies, daily sterilization may not be necessary as long as you’re thoroughly cleaning parts with soap and water after every single pumping session.
Even if your baby is healthy and older, every part still needs a full wash with hot soapy water and a dedicated brush after each use. Sterilization is the extra step on top of that cleaning.
Why Sterilization Matters
Breast pump parts that aren’t properly cleaned can harbor dangerous bacteria. The CDC has documented a fatal case in a premature infant linked directly to contaminated breast pump equipment used at home. Genetic sequencing confirmed the bacteria recovered from the infant matched the strain found on the family’s pump parts.
The bacterium involved, Cronobacter sakazakii, causes severe bloodstream infections and meningitis in young infants. Nearly 40% of infants who develop meningitis from this organism die, and many survivors experience lasting neurological damage. Very young and premature babies face the highest risk because their immune systems and digestive tracts are still developing. Thorough cleaning and regular sterilization are straightforward ways to reduce this risk.
Sterilization Methods That Work
You have several options, and all are effective when done correctly:
- Boiling: Place disassembled parts in a pot of water, bring to a rolling boil, and keep them submerged for five minutes. Use tongs to remove them and place on a clean surface to air dry.
- Steam sterilizer bags or countertop units: Microwave steam bags and electric steam sterilizers are widely available and designed specifically for baby feeding equipment. Follow the manufacturer’s time instructions.
- Chemical sterilization tablets: Sodium hypochlorite tablets (sold under brands like Milton) dissolve in cold water and sterilize parts through soaking. Prior cleaning is essential because milk residue can reduce their effectiveness. Research on these tablets has found no demonstrated risk of intestinal irritation or developmental harm when used at recommended dilutions, though thorough draining before use is important.
Whichever method you choose, always wash parts with soap and water first. Sterilization works on clean surfaces, not on dried milk residue.
Drying and Storage After Sterilizing
After sterilizing, place parts on a clean, unused dish towel or paper towel and let them air dry completely. Don’t rub them dry with a cloth towel, which can transfer germs back onto freshly sterilized surfaces. Once dry, store parts in a clean, protected container or sealed bag until your next pumping session. Reassembling parts while still damp and sealing them in a bag creates a moist environment where bacteria can regrow.
When to Replace Parts Entirely
Sterilization keeps parts safe, but heat and repeated use degrade silicone over time. Worn parts don’t just harbor bacteria more easily; they also reduce suction, which means less milk output. Here’s a general replacement schedule:
- Valve membranes: Every 2 to 4 weeks if you pump three or more times daily. Every 2 months for less frequent pumping.
- Duck valves (duckbills): Monthly if you pump three or more times daily, or every 2 to 3 months otherwise. Replace immediately if they look torn, warped, or discolored, or if they no longer snap shut.
- Flanges: Every 6 months, or right away if you spot cracks or tears.
- Backflow protectors: When they lose their stretch, become discolored, or show any tearing or warping.
One tip for extending valve life: some manufacturers, including Spectra, recommend hand-washing valves with hot soapy water and a brush rather than running them through the dishwasher, which can accelerate wear. You can still sterilize them with boiling or steam, but the high-heat dry cycle in a dishwasher tends to be harder on thin silicone.