What causes the level in the toilet bowl to radically change?
 

You flush the toilet and after the water leaves the bowl, the bowl then fills back up until the surface of the water is maybe the size of a dinner plate.

The next day you flush the toilet and the water only fills the bottom neck of the toilet so that the surface area of the water is a tiny fraction of what it was.

The tank on the back of the toilet seems to fill correctly.

One thing did occur, the pressure switch in our well pump died and I replaced it. But it was replaced with the same pressure (40/60) and everything in the house seem to be working the same, except the toilet.

THere's a second toilet in the house, and it's working fine, but it's got a pressure vessel in the tank while the one acting different uses a "kohler canister flush valve"

similar to this
http://mobileimages.lowes.com/produc...e/07759168.jpg

These work great...and are super easy to install.
https://www.amazon.com/dp/B004A9BQMS?ref=nb_sb_ss_w_as-reorder-t1_ypp_rep_k0_1_24&amp&crid=176RHY6B92JBT&amp&spre fix=plumbcraft+toilet+fill+v

A turn knob controls the water height.

have you checked to see if you have turtles in the tank? One flush they could be in the water, another sitting above the water on a log or something.

^^^ Nah...they only sit above water if the sun is out....not the moon.

A really big "load" could drag the water along behind it when you flush so it doesn't come back to the normal height.
(Think about the water level in the S bend)

Does a further flush bring the water level up to normal?

Nope. I even tried pouring water in and it drained out which seems extra weird to me.

Only the turtles with the laser beams on their heads.

And be careful when you're picking wild mushrooms for culinary purposes.

Is it possible you have a broken sewer pipe that's leaking into the ground? I really hope you don't.

This is strange. The level of water in the toilet should always be the same based on the curvature of the bowl and tube going up and over. It’s like a P-trap under a sink. It always stays the same.

Perhaps there is a crack in the toilet somewhere?

Have you looked in the crawlspace?

From time to time I'd find a low water level. Never figured out what causes it.

my (idiotic) first thought was that a vacuum has formed,

Lasers?, Not on their heads, but they shoot from their eyes. SmileWavy





http://forums.pelicanparts.com/uploa...1656200234.jpg

Water. When the toilet fills up higher, it means there is more water in the bowl.

You're welcome. The turtle question is just silly.

Yeah, apparently, all I had to do was post about it, because I just went into the bathroom and the level is back at the norm.

Not silly...turtles know what a full moon looks like.

This. It shouldn't be low. Something is up with the toilet. Check for leaks under there. Does it rock when you are sitting on it, Steve? You do pee sitting down, right?:D rotten support or movements may cause the wax ring to not seal properly. Is crawl space under the toilet accessible? Check for wet spots under there.

got a dog ?

they lower the level by drinking

I can get under and check. I don't want to but I can. I'll check tomorrow.

Not that can reach the toilet

The wax ring may be leaking?