So you’ve finally received your first Blue Bottle Filter. The celebration is over, and most of the confetti has been swept up. You’re holding it in your hand admiring the simple yet inspiring logo on the top cap when you notice there’s a hole in it!? Not a mesh, not a screen, not a semi-permeable membrane, a hole!

Don’t worry, it’s not broken.

This little hole is actually a key component in our Blue Bottle Filter, so, before you call up customer service and demand a refund please give us a chance to explain!

Blue Bottle Filter Parts

First, let’s get familiar with the parts of the Blue Bottle Filter.

Top Cap

  • FDA Grade Material: 21 CFR 177.1520
  • NSF 14, 51, and 61 Ratings
  • BPA Free Plastic
Filter Medium

  • Class 1 Particulate Filter
  • Renewable Coconut Activated Carbon
  • Catalytic Surface Treatment
  • Ionized Resins
Room Temperature Vulcanization Moisture Barrier

  • NSF 51 Ratings
  • FDA Grade Material: 21 CFR 177.2600
Earth Cap

  • FDA Grade Material: 21 CFR 175-178
  • OXO- Degradable (Landfill)
  • Microframentation at 6 months
  • In-house storage approximately 24 months
  • Rapid Breakdown after 36 months

“Gluggers” – Airflow and Filters in 5 Gallon Water Bottles

Today’s top load water dispensers can be described as “gluggers”. They dump water into the reservoir below while desperately trying to pull air back through the same opening, glugging their way noisily into your home and office ambiance. This two-way flow presents quite a challenge. If you simply placed a filter in this pathway air would fill the filter media and become trapped by the microscopic network of pores and channels and render the filter useless. So, we needed to give the air another path.

Air flow in a 5 blue 5 gallon water jug

Stay Balanced: The Role of Pressure

A closer look at the dispenser system’s shows that they work based on a pressure balance. Water leaves the bottle, until the reservoir water level covers the mouth of the bottle. Once water has risen over the bottle mouth, air can no longer enter the bottle and an opposing vacuum forms in the bottle and prevents any more flow.


As discussed, water and air must both leave and enter through the same bottle opening. Opening a simple port on the bottle somewhere else wouldn’t allow the vacuum to form allowing the bottled water to flow out unchecked, spilling over the reservoir and, like the song about the meatball, onto the floor and out the door; so this means we were kind of stuck with letting air into the bottle the old fashioned way.

So we cored out the center of the filter and put a hole in the cap! Brilliant. The End.


Still here? Yea, we didn’t really think that would satisfy your curious mind so now we’ll tell you the fun cool part.

The Air-plug

By using a very dense filter, we slow the flow of water so much that the air needed inside the bottle can enter much more slowly – these two slower flows no longer need to compete for space in the literal and figurative bottle neck. No more glugging!! As the reservoir fills and the flow in both directions stops, a little bit of air stays at the top of the filter, trapped by the dense filter walls and the water pressure in the bottle. Due to the balanced pressures of the air and water, the top hole is now “plugged”!


And there you have it. The basic science behind our, and soon to be your, filter for 5 gallon water bottles: the Blue Bottle Filter.