Closed System Breast Pump: What It Means and How to Choose
A closed system breast pump has a barrier between the part that collects milk and the motor side of the pump. The barrier is designed to stop milk, moisture and droplets reaching the tubing and mechanism. An open system has no such barrier, so milk can travel into those parts. This guide explains the difference, what a closed system does and does not do, how to clean one, and what to check before you buy.
TL;DR
- A closed system pump has a barrier (a membrane or backflow protector) that is designed to keep milk out of the tubing and motor.
- An open system has no barrier and is for one user only. A closed system is not automatically safe to share.
- Every user needs their own milk collection kit, whatever the system type.
- A closed system does not replace cleaning, sterilising or a well-fitting flange.
- Check the manufacturer’s instructions and product page for the system type before you buy, especially if the pump is pre-owned.
Table of Contents
- What a closed system breast pump is
- Closed system vs open system
- What a closed system does and does not protect against
- Buying or borrowing a pre-owned pump
- How to clean a closed system pump
- System type is not the same as fit
- Questions to ask before you buy any pump
- Perspective
- Wearable pumps and the day-to-day
- Shop Wren pumps and parts
- FAQ
- Sources
What a closed system breast pump is
A closed system pump has a membrane that stops milk droplets getting into the pump, according to NCT’s guidance on expressing and breast pump types. NHS guidance from Birth in Grampian describes the same idea: the barrier prevents milk contacting the tubing or the pump mechanism.
In practice, an electric pump has three zones:
- The collection side. The breast shield (also called the flange), valves and the bottle or bag that holds milk. Milk touches these parts.
- The barrier. A membrane, diaphragm or backflow protector, depending on the model.
- The motor side. The motor and, on many pumps, the tubing that carries suction.
With a closed system, milk should stay in zone 1. The aim is that zone 3 stays dry and free from milk residue.
Names vary between brands. You may see “backflow protector”, “diaphragm”, “membrane” or “hygienic barrier”. They describe the same job. If a product page does not say which type the pump is, the instruction manual should.
Closed system vs open system
An open pump has no barrier stopping milk entering the tubing or mechanism, and Birth in Grampian notes that it is for single-user use only. A closed system keeps milk away from those parts, but the same guidance points out that some closed pumps are still designed for one user.
| Feature | Closed system | Open system |
|---|---|---|
| Barrier between milk and motor | Yes | No |
| Milk can reach tubing or motor | Designed to be prevented | Possible |
| Suitable for sharing the pump body | Only if the manufacturer says so | No, single user only |
| Needs its own collection kit per user | Yes | Yes |
| Cleaning of tubing | Usually only wiping, if milk has not touched it | May need more attention if milk has entered |
The table shows why people search for this term. Most parents are not trying to learn pump engineering. They want to know three things: will milk get into the motor, can the pump be used for another baby, and how much cleaning does it need. The sections below answer each.
What a closed system does and does not protect against
Hong Kong’s Family Health Service says closed systems can decrease the risk of contamination and cross-infection, while open systems may retain milk in the pump and are suitable only for personal use. That is the real benefit: less chance of milk, and anything growing in it, collecting in parts you cannot easily see or wash.
A closed system does not:
- Remove the need to clean the collection kit. Any part that touches milk still needs washing and sterilising.
- Make a pump shareable by default. Sharing depends on the manufacturer’s instructions. UK infection-prevention guidance from the Healthcare Infection Society and Infection Prevention Society says each mother should have her own milk-collection kit, and that kits should not pass between mothers unless sterilised in a Sterile Services Department between users.
- Fix a poor fit. Flange size and suction comfort are separate from system type (more on this below).
Think of the barrier as one layer of protection, not the whole routine.
Buying or borrowing a pre-owned pump
Pre-owned pumps are the situation where system type matters most. NCT advises checking the instructions and, if you are buying a pre-owned pump or plan to use one for another baby, checking whether it uses a closed system.
A sensible checklist:
- Find the model and read the manufacturer’s instructions. They say whether the pump body may be used by more than one person.
- Confirm the system type. If the instructions do not say, treat the pump as single-user.
- Replace the whole milk collection kit. The Hong Kong guidance states that a shared closed-system pump should still be used with each user’s own clean accessories, including breast shields and tubing.
- Check that replacement parts are available. The same guidance suggests choosing durable, replaceable parts. Our page on breast pump spare parts explains what typically wears and when to replace it.
- Inspect the pump for damage. Cracks, loose housings or a damp motor side are reasons to walk away.
If you are buying new, the question is simpler: pick a pump whose instructions are clear about its system type and about which parts you replace.
How to clean a closed system pump
Cleaning is shorter than for open pumps in one respect: if milk has not touched the tubing, it generally needs wiping, not washing. It is not shorter in the parts that matter.
The Scottish perinatal network’s parents’ guide to electric breast pumps sets out a routine you can follow:
- Wash your hands and separate the pump-set parts.
- Rinse the breast shield and connector.
- Wash them thoroughly in warm soapy water, then rinse again.
- Dry with a fresh paper towel.
- Store the parts separated, in a clean covered container.
The same guide says tubing, and the cap on the Symphony pump it describes, do not need washing when they have not contacted milk. They should be wiped with detergent wipes before use. The pump itself should be wiped with detergent wipes or household detergent before and after each use.
For sterilising, the NHS says the pump, bottles, valves and funnel should be clean and sterile before use, and that the pump and its parts should be washed and sterilised after expressing.
The UK joint infection-prevention guidance adds why this matters: kits should be completely dismantled and decontaminated after every use, because parts that stay wet can support hazardous bacterial growth.
Two of our guides cover the practical side: how often to sterilise your pump and how to clean and sterilise a Wren pump. Always follow the instructions for your own model first.
Signs a barrier needs attention
If milk or moisture appears on the motor side, stop using the pump and read the instruction manual. Some barriers are replaceable parts. Do not keep expressing on a pump you suspect is contaminated, and contact the manufacturer or retailer for guidance.
System type is not the same as fit
Choosing a closed system answers a hygiene question. It does not answer a comfort question. NHS clinicians at Birth in Grampian make this point: a well-fitting flange makes expressing comfortable and helps minimise the risk of blocked ducts. The same guidance warns that removing more milk increases milk production and may overstimulate the breasts, so more pumping is not always better.
Three habits help:
- Check the flange size. If expressing hurts or milk output seems low, fit is the first thing to look at. Our guides on spotting a wrong flange size and choosing the right flange walk through it.
- Start low. The NHS advises starting an electric pump slowly on the lowest or a comfortable suction setting, and increasing the speed only once milk starts flowing and it feels comfortable. Our piece on finding a comfortable suction strength explains how settings are usually expressed.
- Read the manual. NCT notes that electric pumps copy a baby’s sucking motion and that you should refer to the manufacturer’s instructions for your model.
If you have pain, nipple damage, a lump or signs of mastitis, speak to your midwife, health visitor, GP or an infant feeding specialist. Pump settings will not solve those.
Questions to ask before you buy any pump
A closed system is one line on a longer list. NCT suggests considering the pump type, power, portability and intended use. Use these questions:
| Question | Why it matters |
|---|---|
| How often will I express? | Occasional use suits a different pump from daily work-day expressing. |
| Where will I express? | At home, at work or while travelling changes how much portability you need. |
| Is the system closed or open? | Affects how milk can reach the motor and whether the pump body can be shared. |
| Are replacement parts easy to buy? | Valves, membranes and shields wear and need replacing. |
| Does the flange come in several sizes? | Fit affects comfort and output. |
| How is it cleaned? | Fewer parts that touch milk means a shorter routine. |
If you are not sure whether you need a pump yet, our guide Do I need a breast pump? sets out when one helps. For a wider look at electric options, see choosing an electric breast pump that fits life.
Perspective
Parents often ask us whether a closed system is the one feature to look for. We see it as one of several. The barrier matters, but so do the parts you replace, the flange that fits you, and a pump you will actually use day to day.
Our own focus is on wearable, wire-free pumps that sit inside the bra, so expressing can happen at home, at work or on the move without being tied to a wall. For many mums, a pump that fits into the day is the pump that gets used.
Our advice is practical. Read the manual, confirm the system type on the product page, size the flange properly, and keep your cleaning routine steady. Those habits protect your milk and your comfort far more than any single label.
Paul
Wearable pumps and the day-to-day
Hands-free pumps change what “fits your life” means. A wearable pump sits inside a bra, with no tubing running to a separate motor, so you can express while working, caring for your baby or travelling. That is the design purpose of our range.
Whatever the design, the same checks apply: confirm the system type in the product details and manual, use your own clean collection parts, size the flange, and follow the cleaning steps for your model. Our comparison of pump suction levels helps if you are weighing settings across models.
After birth, expressing sits alongside general breast care. Our postpartum breast care guide covers the feeding days.
Shop Wren pumps and parts
We make hands-free, wire-free electric breast pumps for mums in the UK. You can see the full range in our breast pump collection, or go straight to the hands-free double electric pump or the hands-free single electric pump. Product pages carry the specifications, so check them for the details you need.
If you already have a Wren pump, replacement parts are in our spare parts collection. For kits that bring the basics together, see breastfeeding kits and breastfeeding accessories, including milk storage bags and nipple care.
FAQ
What is the difference between a closed and an open breast pump?
A closed pump has a barrier that stops milk reaching the tubing and motor. An open pump has no barrier, so milk can enter those parts, and it is for single-user use only. Check the instruction manual for the system type of any model you are considering.
Can two mums share a closed system breast pump?
Only if the manufacturer says the pump body can be shared, because some closed pumps are designed for one user. Even then, each person needs their own clean milk collection kit, including breast shields and tubing. UK infection-prevention guidance says kits should not pass between mothers without sterilisation between users.
Do I still need to sterilise a closed system pump?
Yes. The NHS says the pump, bottles, valves and funnel should be clean and sterile before use, and washed and sterilised after expressing. The barrier reduces what reaches the motor side. It does not clean the parts that touch milk.
Does a closed system make expressing more comfortable?
No. Comfort depends mainly on flange fit and suction setting. A well-fitting flange helps reduce the risk of blocked ducts, and the NHS advises starting on a low, comfortable setting. If expressing hurts, speak to your midwife, health visitor or an infant feeding specialist.
How do I find out whether my pump is closed or open?
Read the instruction manual and the product page. Look for terms such as backflow protector, diaphragm or membrane between the collection kit and the motor. If the documents do not say, contact the manufacturer and treat the pump as single-user until you know.
Sources
- NCT: Expressing breastmilk and different kinds of breast pumps
- Birth in Grampian (NHS): What is the difference between breast pumps?
- Family Health Service, Hong Kong: What You Need to Know about Breast Pumps
- Perinatal Network Scotland: Parents’ Guide to Using an Electric Breast Pump and Milk Collection Kits
- NHS: Expressing breast milk with a pump
- Decontamination of breast pump milk collection kits and related items at home and in hospital (PMC)
