Breast Pump Diaphragm Replacement: Signs You Need a New One and How to Install

Quick Answer

If your pump's suction feels weak or you notice milk leaking, it's likely time to replace the diaphragm. Check the diaphragm for tears or stretching, and swap it out every 1-2 months with regular use. Follow the steps below to install a new one and restore optimal performance.

Your breast pump's diaphragm is a small but critical part that helps create the suction needed to express milk efficiently. Over time, it can wear out, stretch, or tear, leading to decreased suction and frustration during pumping sessions. Knowing when to replace it and how to do it correctly can save you time and keep your milk supply consistent.

In this guide, we'll walk you through the common signs that your diaphragm needs replacement, provide step-by-step installation instructions, and share tips to extend the life of your pump parts.

Signs Your Diaphragm Needs Replacement

A worn diaphragm can affect pump performance without being obvious at first. If you notice reduced suction, longer pumping times, or a decrease in milk output, inspect the diaphragm for visible damage. Look for small tears, holes, or a stretched shape that no longer fits snugly.

Another clue is if you hear a clicking sound during pumping or see milk backing up into the tubing. These symptoms indicate that the diaphragm isn't sealing properly. As a general rule, replace the diaphragm every 1-2 months with regular use, or immediately if you notice any of these signs.

• Check diaphragms after each use for signs of wear.
• Keep a spare set of parts on hand for emergencies.

How to Replace Your Breast Pump Diaphragm

Replacing the diaphragm is a straightforward process that you can do in minutes. First, ensure your pump is unplugged and disassemble the parts that connect to the breast. Remove the old diaphragm by gently pulling it off the valve or flange, taking care not to damage other components.

Before installing the new diaphragm, wash your hands thoroughly. Align the new diaphragm with the valve or flange and press it firmly into place. Make sure it sits flat and seals completely. Reassemble the pump and test it to confirm suction is strong and consistent.

• Always follow the manufacturer's instructions for your specific pump model.
• If you're unsure about compatibility, check the model number before purchasing replacements.

Step-by-Step Diaphragm Replacement

1. Gather your supplies: You'll need a new diaphragm, a clean towel, and access to your pump parts. Check your pump manual for the exact part location. Keep a spare diaphragm in your pumping bag.
2. Disassemble the pump: Unplug the pump and remove the flange, bottle, and tubing. Locate the diaphragm—usually attached to the valve or flange. Take a photo before disassembly to help with reassembly.
3. Remove the old diaphragm: Gently pull the old diaphragm off. Inspect it for tears or stretching, and note any residue that might indicate a problem. Discard the old part properly.
4. Install the new diaphragm: Align the new diaphragm with the valve or flange and press it on securely. Ensure it's seated evenly and there are no gaps. Double-check the seal before reassembling.
5. Reassemble and test: Put all parts back together, plug in the pump, and run a quick suction test. If suction feels strong and even, you're ready to pump. If suction is still weak, check other parts like valves or tubing.

Products to Help with Diaphragm Replacement

• Pump Valves - 4 Pack for Signature Pro and Smartpump: These breast pump valves attach to the flange body and work with the diaphragm to ensure proper suction. Lansinoh valve replacements are compatible with Smartpumps, Signature Pro®, and Lansinoh® Manual Breast Pump. If your diaphragm is worn, the valve may also need replacing. Having a 4-pack ensures you have spares ready for both pumps.



• Thrive 2-in-1 Breast Pump Valve for PowerPump & Wearable Pump: A spare set of parts when you need them! Great to have on hand when you’re pumping away from home and need an extra set of clean parts. Or keep it on hand to replace parts that wear over time. This valve set is designed for the Thrive pump system, so you can replace the valve and diaphragm together for optimal performance.

Regularly inspecting and replacing your breast pump diaphragm keeps your pump working efficiently, which supports your pumping goals. By catching the signs early and following the simple installation steps, you can avoid interruptions and maintain consistent milk output. Remember to keep spare parts like valves and diaphragms on hand so you're always prepared.