On 12/7/2010 5:43 PM, Red wrote:
On Dec 7, 4:21 pm, wrote:
On Dec 7, 5:14 pm, wrote:

On Tue, 7 Dec 2010 10:30:24 -0800 (PST),
wrote:

I call it toilet tide, but what is it when the level in the toilet
drops an inch or so? It is the atmospheric pressure, wind blowing
across the vent tube creating a little more vacuum, clogged vent, low
water in the back, or something else? It's no big deal, just curious.

Hank

It is virtually always vent related. You may have enough wind in the
vent to "rock" the water out or you may have bad venting allowing
water retreating from another source to suck the water out.

First to all, I don't have any animals.

Second, I can dump a half gallon of water into the toilet and the
level stays up. The water level in the tank has been consistant. There
is a minor wind of maybe 10 mph. The house is about 5 years old, but I
guess there could still some obstruction but the other 2 toilets seem
ok.

Hank~~~ wants to elevate to a higher level :-)

Mine have always done that with a strong intermittent wind blowing. I
think it's pressure related - the wind blowing across the vent pipe
sucks the air from the pipe, causing lower pressure in the pipe than
in the house. The water tries to move to the lower pressure. Then
the air rushes back into the vent pipe, causing the water to return to
it's normal level. The result is minor wave action.

Most likely. Figure it out. Atmospheric pressure is approximately 14
psi, enough to lift a column of water 32 feet. If my math is correct as
little as 0.05 psi pressure differential could move the water over an inch.