# Soda fountain noises

**URL:** <https://boards.straightdope.com/t/soda-fountain-noises/707909>\
**Category:** Factual Questions\
**Created:** [December 22, 2014, 2:25pm UTC](https://boards.straightdope.com/t/soda-fountain-noises/707909 "2014-12-22T14:25:06Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\
**Post date:** [December 22, 2014, 2:25pm UTC](https://boards.straightdope.com/t/soda-fountain-noises/707909/1 "2014-12-22T14:25:06Z")

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Every now and then I visit a restaurant in which the soda fountain releases a burst of gas at fairly regular intervals while dispensing soda. The sound is like the violent hiss of a truck’s air brakes (tho not nearly as loud). The noise doesn’t come from the dispensing nozzle;it seems to emanate from the array of bottles and tubes next to the soda fountain.

What’s this noise? Venting CO2? Why?

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**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\
**Post date:** [December 22, 2014, 2:46pm UTC](https://boards.straightdope.com/t/soda-fountain-noises/707909/2 "2014-12-22T14:46:08Z")

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Possibly a bad high-pressure regulator on the CO2 system. It can’t maintain the lower infusion pressure (around 80-100 psi, IIRC) from the high-pressure tank (1200-2500 psi?) without venting excess pressure. (Complete TWAG…)