faucet water igniting
>> What's the cause of those youtube videos of people
>> igniting their water mains, if it isn't fracking?
>A pre-existing geological condition.
Maybe...in some cases the water table used for drinking water wells is not saturated with methane or other gasses (the vertical separation may be thousands of feet). When a fracking operation drills through a "cap" to get to the shale to be fracked, they surround the pipe (which will carry the gas) with a cement protective ring. Without this ring, methane from below the cap "creeps" up the side of the pipe until it reaches the water table. It then enters the water - because the water is an easier "escape route" than continuing up the side of the pipe.
A well-designed (i.e.thick enough and high quality cement) casing around the pipe prevents the gas seepage from happening. Bad or failed casings allow clean water to become saturated with gas - these are the flaming faucets that appear on YouTube.
How many cement casings fail? Some say that records from the frackers themselves indicate that 5% or so fail before completion of the drilling. Who knows? And how many will fail in a year? Or 2? Or after a very minor quake?
What are the real figures? Perhaps the fracking industry will someday reveal that to us.
Until then, we will just have to trust them.
Of course, if methane suddenly starts to come out of your faucet (when it never did before) you may not feel so trusting.
[warning: some technical details were simplified in order to prevent this post from being deadly boring]