I have an older Gerber brand toilet. The black rubber seal that looks like a Mason jar lid is crumbling and turning into black goo when touched. Is it easy to replace this? What is the purpose of this part? Will an American Standard one fit on a Gerber? Is there a way to keep these from disintegrating? Any help with information on this part would be appreciated. Thanks.
Toilet valve black rubber seal disintegrating
toilet
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It seems as if you have an obstruction that may be floating around in the pipe or valve. Sometimes it obstructs sometimes it flows clear. I would start with changing the water valve. If this is the old style "gate" valve there are several things that can clog the line. I would replace it with a 1/4 turn ball valve. That will give you much better flow than a gate valve. You will need to shut down the water probably at the main. The old valve is probably soldered, but you could cut it off and use a compression type valve instead. "Sharkbite" is one such supplier. Although I have never used their compression valve, I have used their end caps and found them to work well.
If you can have someone hold a bucket under the pipe once you cut off the valve and then a second person turns on the water main to fill the bucket to purge the line of any debris. With cast iron pipes it is common to get clogs from rust build up. The rust may not pass the small opening in the old gate valve when you first purged the line.. Although you did not mention what type of pipes you have, if it's copper than you won't normally find rust obstructions..
The image attached to this answer, shows what the flush valve is.
It typically includes the overflow tube, but more specifically it's the flapper (or a device that controls the flow of water into the bowl).
Measure the tank discharge (flush) tube (the hole the flush valve (flapper) covers), to determine the size flush valve you need. The hole might be slightly larger or smaller then 2", but close enough is close enough.
Best Answer
It's unclear exactly where this seal is without pictures, but in general they are all replaceable, ease of replacement varies (sometimes you have to take the tank off the toilet to replace seals), and you had better try to find one made for your specific brand/model of toilet, as between manufacturers there are often incompatibilities. An actual plumbing supply may have a better selection of parts than a big box store.
Some replacement seals are offered in a "chlorine resistant" rubber formulation (often red) but in general, rubber at 30-50 years old does simply tend to fail from old age. If you are one of those people that puts an extra-chlorine "toilet cleaner" in your tank, you might expect to have faster aging of rubber and plastic parts as a result. Even if you do not add extra chlorine, they do not last forever.