Spectra S2 Assembly: Ultimate Guide In Putting Your Breast Pump Together

Spectra S2 Assembly: A Step-By-Step Guide

Whether you are looking at purchasing a breast pump, or already have yours, my handy guide will show you how to assemble the Spectra S2. My step-by-step pictures will help you get your pump together quickly and easily!

Spectra S2 assembly is very simple. Let’s walk through it together!

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List of parts that come with the S2

Click the image to see more details on Amazon

First, let’s take inventory of everything that comes with the S2 breast pump. Your kit likely includes a bag, power adapter, four 5 ounce bottles, 2 backflow protectors (two sets of: two clear hard plastic pieces and one white silicone membrane), two duckbill valves (triangular white silicone parts that create the vacuum seal), 2 tubes, two 24mm flanges (the “shields” that go onto your breasts), two 28mm flanges, and a cooler. 

Some kits do not include the tote bag or cooler, depending on what version you select.

Cleaning the S2 Parts

First, you will need to wash the bottles, all the pieces of the backflow protectors, the valves, and the flanges. You may want to wash both sets of flanges to determine which one fits you better. Do not wash the tubing.  Spectra recommends:

For the accessories (which are clear or pink) — breast shield/flange, upper and lower case of backflow protector, bottle, bottle ring, bottle cover, and disk: (your model may or may not have all of these accessories) 

1. Use a pot large enough to fit all your parts—if the pot is too small, parts discoloration and/or distortion may occur.

2. Fill with water so that when your parts are added the water is at least 4” above the parts.

3. Place lid on the top and bring to boil.

4. Once the water reaches boiling point, turn off the heat and place accessories in boiling water—the water will continue to boil.

5. Remove accessories after 3-5 minutes.

6. Silicone Accessories–duckbill valves, backflow protector membranes, and bottle nipples: Run them through the boiling water for less than 2 minutes.

That’s pretty straightforward!

If you prefer, you can sterilize your parts in the microwave or dishwasher. 

Microwaving your parts can result in distortion and/or discoloration of the parts. Discoloration is cosmetic and does not affect the chemical composition of the parts.

Microwave bags can be used if the proper amount of water is added. Follow the instructions of the bag manufacturer.

Or, if you want to use a steam bag to sterilize your S2 parts, check out the Medela Quick Clean Micro-Steam bag (click to view on Amazon)! Simply put the parts in the bag with some water and microwave them. The steam will sterilize the parts!

Click the image to see more details on Amazon

And Spectra explains that you can put your parts in the dishwasher!

If using a dishwasher, place items on wash cycle on the top rack and air dry. Do not use heat dry.

Drying all the pieces and parts

Next, no matter how you wash your parts, you will need to dry them. I like to set my pump parts and bottles up to dry on this cute drying rack from Amazon that looks like fake grass.

drying rack for breast pump parts
Why yes, I am good at Tetris. Why do you ask?

Now that everything is clean, we can get on to the Spectra S2 assembly, starting with the backflow protectors. 

Spectra S2 Backflow Protector Assembly

Spectra S2 backflow protector assembly looks tricky but is actually super simple. 

spectra s2 backflow protector assembly
Left: small backflow protector piece. Middle: white silicone backflow protector membrane. Right: large backflow protector piece (note the small tab at the bottom)

First, you can see the backflow protector has three pieces- two are the clear, hard plastic cases and one is a white silicone membrane. The two clear pieces are slightly different. One has a tab on the outside to help you disassemble the backflow protector, and is a little wider in diameter. The other doesn’t have the tab, and is smaller.

s2 backflow protector assembly 2
First, put the small part of the backflow protector on the membrane

Start with the smaller diameter clear piece and the white silicone membrane.

s2 backflow protector assembly step 3
Check that the white silicone is pulled tight around the outside of the small plastic backflow adapter piece

Fit the membrane around the outer edge of the clear plastic. You may need to push or tug it into place so it is fully sealed. Got that? This was the hardest part!

s2 backflow protector assembly step 4
Then put the large piece of the backflow adapter on the other side

Now put the other clear plastic part on the back side. It should snap right into place.

s2 backflow protector assembly step 5
Insert the small end into the tubing

Just stick the smaller end of the backflow protector onto the tubing. Only one end will fit into the tubing. The other end will go into the back of the flange later.

And you’re ready to go! Though you may want to assemble the other backflow protector now too if you are planning to pump both sides at once.

How to Assemble the Spectra S2: Putting it All Together

spectra s2 tubing
Fit the tubing into the vacuum ports

Now that you’ve assembled the backflow protectors, you’re nearly done! Insert the other end of the tubing over the vacuum pump outlet. If you plan to pump both sides, remove the cover from the other pump outlet and hook up the other tube too.

Next, plug the power cord into the wall… and now your Spectra S2 assembly is complete! 

To assemble the bottles, first put the silicone duckbill valve onto the bottom of the flange.

If you’re ready to pump now, you can assemble your bottles as well. First, put the white duck bill valve onto the bottom of the flange. Then screw the flange onto your bottle. Last, insert the other end of the backflow protector into the back of the flange. Finally, you’re ready to pump! 

Spectra S2 Tips

Check out my post with 35 Spectra S2 tips for the full details. Here’s the short version:

  • When you start pumping with the S2, press the button with the two squiggly lines. The two squiggly lines will appear on the LED screen. This puts the pump in expression mode to encourage letdown and get milk flowing. Once milk starts flowing, press the button again to put the pump into normal mode.
  • Keep a spare set of membranes, valves, and tubing on hand because something may break or you won’t have time to wash items between pumping sessions.. And replace them every 3 months or so because these parts can wear out over time. This causes the pump to work less effectively, meaning you get less milk. Replacement parts from Spectra are readily available on Amazon!
  • The Spectra S2 has a little “cup holder” on the back. You can use it to wrangle the backflow adapters, or fit a bottle into it.
Check out the handy cupholder on the back of the S2!

Related post: Check out activities that will keep you from getting bored during pumping or breastfeeding


Sanitizing and putting together the Spectra S2 is super straightforward! I hope this step-by-step guide helped you! I had never seen a breast pump before I had my baby, so this was all very intimidating. But it is actually pretty straightforward!

Best wishes on your pumping journey!

Related post: Tips On What To Do With An Old Breast Pump

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