Drain stopper I just purchased a drain stopper for my kitchen sink, It does not stop the water from draining. It is not flat Could that be the problem?

If for a kitchen sink, measure the depth of the cup and diameter. Most hardware stores sell replacement stoppers.
If for a bathroom sink, look at faucet manufacturer and look online for replacement part.
For a quick fix for both / need a solution now to plug the sink, I have used in the past Saran Wrap is a pool plug rubber stopper that comes in a variety of sizes and fits both kitchen sink (larger one like size 10 or 11) or bathroom sink (size 6 or 8).
Good luck!

Are we talking about a sink drain or a floor drain? If its sink drain there is a stopper on the top and have to released from under the sink. The pipe underneath will have a 90 degree connection with a rod metal or plastic piece connected to the pull rod. Disconnect and it will free the stopper for cleaning. If a kitchen sink the piece is attached with plumbers puddy and a nut from under the sink. I would say its not worth cleaning or messing with it. If it's a floor drain. There is screws or a drop insert. Remove screws to release or simply lift out with a screw driver. Hope it helps.

there is a rod under your sink which controls the travel of the stopper it needs to be adjusted for shorter travel.

the waste disposal system for your house was installed by a person who was not competent to do the job and didn't make allowances for sufficient air pipes in the system or placed them on the wrong side of the traps
I would have an engineer inspect the installation to pin point the problem so that what you have doesn't occur and if it is installed contrary to plan and engineering requirements seek legal redress from the plumber that did the job

follow this steps and fix it. God bless you
lear a clogged (not stopped) sink or bathtub with a plunger:

1. If you have a dishwasher, pinch off the rubber dishwasher drain hose that leads to the garbage disposer using a clamp or locking pliers. If clearing a bathtub, remove the drain stopper and cover the overflow opening with a wet rag.
2. Remove the sink basket or tub stopper and clean any debris from the drain opening.
3. Fill the sink or tub with sufficient water to cover the plunger cup, usually about 2 inches. If you are working on a double sink, seal the other sink with a stopper so the plunger can create a vacuum.
4. Set the plunger on the drain opening and repeatedly pump it up and down, then pull away sharply to dislodge debris. Repeat if necessary.
5. Turn on warm or hot water to flush loosened debris from the drain.
6. If the clog remains, use an auger (see below) or an expansion nozzle (see below) to clear the drain.

Clear a clog using an auger:

1. Remove the stopper or strainer. If unable to do so, disassemble the drain trap (see below) and feed the auger directly through the pipe. Make sure you have a pail and rags nearby in case of a water spill.
2. Release the setscrew on the auger and begin feeding the cable into the open drain.
3. Once the auger tip hits the clog, set the screw and crank the auger clockwise to break up the clog.
4. Continue breaking up the clog and moving it down the drain line with the auger. Once there is no more resistance to forward motion of the auger, stop and carefully remove the auger.
5. If the clog can't be moved, continue twisting the auger to possibly snag and retract the clog.
6. Once the clog is cleared, flush the drain with boiling water.

probably hair stuck in the drain. did you remove the stopper "pop up" if no hair or blockage there or in the trap, then its further down, you will need a small snake. 1/4 inch cable works well in bath and kitchen drains.
you can purchase one at home depot.

Sounds like plumbers putty un drain flange to sink may need to be replaced or strainer may need to be tighten up a little to see if that stops the leak.

You shouldn't have to disassemble everything in order to get to the trap (elbow joint). Most pedestal sinks are designed so that you can get to the trap from the back (generally after getting down on your hands and knees and crawling around with a flashlight). Most sink stoppers that are worked from the faucet itself have a little bar that extends down the back of the sink behind the drain. It will clip with a little metal piece to a lever that sticks out the back of the drain before the trap. The lever goes through a hole in the drain and pokes into a hole in the bottom of your sink stopper. As you move the lever, you will notice that your stopper goes up and down.

Unclip the rod from the lever and you should be able to unscrew the lever from the back of the drain (don't loose the little gasket that sits inside the screw-cap as it keeps water from leaking out here). At this point, you can pull out the stopper and see what is going on. If cleaning off the stuff attached to your stopper doesn't solve the problem, you can then remove the trap to see if anything is clogging that. Hopefully, by this point, your sink clog has been identified and you just need to reassemble, making sure when you put your stopper lever back in that you actually get it into the appropriate hole in the stopper itself.

If this doesn't solve your problem, it's more serious and you probably want to call a plumber as the issue is either a clog farther along or a problem with the venting of the sink drain.

make sure that the piece going in to the drain that moves your stopper up and down is all the way in the hole on the bottom of the stopper once that is in hold the rod down so your stop is up then attach it to the piece attached to your rod this should solve your problem good luck

dishwasher drain enters sewer system tapped into waste pipe below kitchen sink
water flowing from kitchen sink passes the opening of the dishwasher pipe
If the dishwasher hose does not loop up higher than the kitchen sink before going down to the bottom of the dishwasher water may flow downhill through the dishwasher drain into the dishwasher
ensure the dishwasher drain hose is screwed to the underside of the kitchen counter, to provide a stop to water flow.
The installation instructions suggest this
but often the dishwasher is at the end of its 'stretch'
and the installer assumes looping is just to use up excess hose, and doesnt.
an extension drain hose is available at most appliance stores