Re: What causes water to gurgle in pipes?

Pipes start off full of air.  When you pour water down the drain 
(especially a lot of water....enough to fill the diameter of the pipe) 
air in the pipe gets trapped and tries to escape past the much heavier 
water to make room for the water to go down.  What your 
hear as gurgles is the sound of the sloshing water as the air rushes past 
it - it is also made to sound somewhat hollow due to the 
enclosed nature of the pipes where it is coming from. 

As to why you hear this gurgling sound from other drains in the house - 
they are all connected (either by branching pipes along the 
way down or at the sewer drain under your house).  The sound travels from 
the drain that is gurgling and through the pipes to the 
other drains.  This is just like in the movies if you have seen people 
trapped in the basement (or someplace like that) and they are 
tapping S.O.S on the pipes so someone upstairs will hear them and come to 
the rescue. 

Now, this just occurred to me, if you are referring to the gurgling of 
water up through adjacent drains, this is something a bit 
different....but not really.  Because the pipes are all connected, water 
flowing forcefully down one drain can be pushed up 
another.  However, this is all dependant on the pressure of the water 
draining.  I could see water coming up an nearby drain (one 
at or near the same elevation as the one draining), but it is not very 
likely to see water that is draining in the basement to come 
gurgling up a second floor sink.  If this were to happen, I would not 
recommend standing too close as there would be A LOT of 
pressure involved!    :-) 

I hope this answers your question for you.  If you have any further 
questions about this, please feel free to email me. 
 

     Kurt Frost 
     kfrost@sympatico.ca