toliet running out of the blue / help please

we have a Elgar 1.6 gal/6lpt toliet tank#141-250

and it just starts running out of the blue....What do you think is causeing this ? thanks

last night it woke me up twice and I had to shake the handle or flush it to get it to quit...

When the flapper goes bad, the water from the tank is slowly leaking into the bowl and thus down the drain. Replacement is very common.

Correct. Most likely, you have a leaky flapper, which is the little device that gets pulled open when you pull the chain. It's easy to find the right one to replace it at Lowe's. It only takes a few minutes to install, and is the easiest thing to fix in your toilet. For a generic toilet, a regular Korky Plus flapper does a great job.

Easiest way to check whether the flapper is leaking is to turn off the water to the toilet at the wall, open the lid, and mark the level with a pencil. Wait 30 minutes or more. If the level of water in the tank has dropped, you have a leak. Most likely, it's the flapper. (It could be some other things, and we have had some fun here diagnosing more complicated problems, but 99 percent of the time it's the flapper.)

Here's a link to the Korky web site: http://korky.com/anatomy.html You can also call them at 1-800-528-3553 with your toilet's make and model, and they will tell you which flapper to get at Lowes or HD. Nice folks in Wisconsin. Korky stuff is made in the US. Good luck. Come back if you have any more questions.

it was the flapper . thanks