Gravity makes it fall down once the water level is low enough that it's not floating. Are you sure it is the right flapper? I've never had to use lubricant on a flapper, but a little plumber's silicon, or even soap and working it several times by hand, might help.
Yes, the tank would have to come off to replace the tube and flapper unit.
My 44 year old toilets are just middle aged. Not stylish or the most efficient, but still do the job.

If by "stays up" you mean fails to seal, check the surface it is closing onto.

It may be rough and need to be cleaned.

There is air inside the flapper stopper part. This helps hold it up while the water drains out. Once the water level in the tank goes down, the flapper falls by gravity and is held in place by the rising water.

Hi, I had the same problem would not seat, it just would float at the seal but would not close. I jumped through all the hoops nothing worked what I found was the water ran out of the tank to slowly. I poured about a quart of muratic acid down the over flow and let it set for about a half hour. Problem cured, You asked what makes a flapper close, well a few things that can be seen but suction plays a major part. I think you have a lime build up in the toilet. Acid will clear it.
Good Luck Woodbutcher

Thanks, well my flapper stands UP, all the way. Maybe my universal flapper was not so universal! It does seal when I poke it down.

so, try a different flapper, try muriatic acid, then if all else fails get a new tube and flapper that are sold as a set. (I hope they come that way).

OK, I'm game. I'm not thrilled about messing with the toilet innards but I'm more mechanically inclined than my DH.

Thank you all!
Smiles,
Rebecca

At least it is clean water.

If your flapper stays up with NO water in the tank, the problem isn't what woodbutcher said, so using the acid won't help. That is for a different problem. Suction only helps seal the flapper once it is already down, not physically push it down.

I'm just trying to help you skip doing something that you may not need to. The first step is getting the flapper to fall down. The next step is to make sure the flapper makes a proper seal.

vegasneon,

As I understand your original post... the original flapper began to stay up and you replaced the flapper with a universal model and the new flapper stays up just the same as the original flapper? Is that correct?

If that is correct then something or someone caused the original flapper to bind on its mount or its the chain and handle binding preventing it from falling. Perhaps the flapper mount was twisted on the tube. It is as simple as that. Since the new universal flapper has not solved the problem you look for the problem elsewhere.

As a side note... universal anythings usually work equally poorly in all applications so always try to find the CORRECT part for your application. You may have bought the wrong flapper. Perhaps a 1.6g flapper and you have the older style toilet? Some toilets designs must have their specific brand replacement flapper.

Sometimes the flush handles bind and sometimes the chains kink or turn on themselves keeping the flappers up.

I have never seen a flapper bind on its pivots or mount but if the water has enough hardness or sediment it could happen.

Shut off the water to the toilet. Flush the toilet to empty the tank. Remove the chain from the flapper. Move the flapper with your hand up and down. It should move FREELY with no resistance other than the weight of the flapper.

If the flapper does not move freely then you don't know what you're looking at and wouldn't recognize the problem so get someone who has a fresh set of eyes or experience to take a look.

I suspect this is an easy fix but not over the net...

Typically the flapper when raised to the maximum possible is not completely vertical, but is at an angle. The air cavity (look at the hole in the bottom when it is raised or inverted before installation) holds it up by "floating" until the water level drops. Could your flush lever be binding and holding the chain taut whenever the flush lever is released?

When you try to push the flapper down by hand, is there any friction? The answer to this would help us figure out if there is any binding in the pivots.

I just had this same issue happen, and noticed that the responses here jump all over the place.

If the flapper does not fall back down (we are not talking about seating tight), then it is either your chain length or something blocking it from falling. Too short a chain length and you pull that flapper all the way up, possibly getting it stuck. Too short and it may not stay up (allowing water to flush) long enough.

Adjust the chain length - it can be a tedious process. Also, make sure extra chain is not hanging down blocking the flapper from seating.

On my toilet, I had bought a decorative handle. The arm that was inside the tank was ridiculously long, and I noticed that when the flapper came up, the arm would catch the lip, causing it to stay open until it eventually slipped off. I cut the arm length back and now it works like a charm.

The weight on the chain sounds very possible, I had sporadic issues for so long I bought a new taller toilet. I wish I had just replaced it before I messed around with it so many times.
Thanks everyone.

I also had the toilet flapper stay in the up position. The chain was fine. Whenever the water filled the tank, the flapper lifted up. I read that gravity holds the flapper down from another comment. So, what I discovered was the water level in the toilet itself just needed to get lowered. I just used a plunger to lower the water level & the flapper closed.

Yay! My flapper stayed up too. I tried cleaning the pivot points, cleaning the chain, etc...looked at a bunch of 'help sites' to no avail but the comment about slipping a washer over the chain was brilliant....just a bit more weight on top of the flapper and it dropped exactly as it should. Thanks!

The flapper is the right model for the one piece Kohler toilet but it doesn't close. It looks like the front is too wide and catches on the side of the tank. Can I trim the edge with a scissors?

Hi had the flapper sticking up as well. Finally caught it in the act. These were adjustable flappers that have a grove on the top for the adjuster. The chain was getting caught around the grove on the top and holding the flapper up. The chain had only a slight slack when properly closed but didn't matter. Still was consistently getting caught on the grove/notch on the top. Switching out to generic/smooth non-adjustable flappers so the chain doesn't have anything to snag on.