Some members here have had some problems with sanitary products described as flushable. During my career in plumbing, I have run into many "flushable" products, and have developed some strong opinions on them. To start with, they are indeed flushable, in the sense that they will go through a toilet that's in good repair, and one that hasn't collected a lot of rough deposits. However, that is far from being the whole story.
Toilets can collect deposits over years of use. This seems be be much more common if the toilet isn't flushed every time it's used, and the uric acid can combine with hard water elements such as calcium and magnesium. These deposits can be very hard and very difficult to remove. They can be removed chemically, but the only chemicals I've seen work effectively are pretty dangerous to handle. These deposits make the passages of the toilet smaller, and also plug up the rim jets and siphon jet so that the water doesn't flow into the bowl quickly enough to give a strong flush.
If the flushable product makes it through the toilet, then there is the drainage system to consider. As has been mentioned, these products don't dissolve the way that TP will dissolve. In fact, some of them don't dissolve at all. If your drainage system is constructed correctly, and not afflicted with heavy deposits or roots, usually things work OK. If, however, there are areas of the pipe that do not have sufficient "fall" or downward grade, these items may settle out and cause trouble, particularly in cast iron pipe. I have found that once the flow of water stops, fibrous materials tend to stick to cast iron, or get caught in rough deposits. Now the trouble begins, as the flow in this area will slow, allowing more stuff to settle out, which increases the restriction, and so on until you have a stoppage. Older cast iron systems which have proper fall will often handle these items. Not always.
The ideal situation is to have a new-ish toilet that works well, and properly installed plastic waste/sewer pipe. Out here in California, ABS pipe is the most common, although we're seeing more PVC recently. My house was built circa 1970, and has a 3" ABS sewer. In the 21+ years I've lived here, I haven't had a sewer stoppage. Anything that will go through the toilet will make it to the city sewer, so "flushables" aren't a problem.
Toilets can collect deposits over years of use. This seems be be much more common if the toilet isn't flushed every time it's used, and the uric acid can combine with hard water elements such as calcium and magnesium. These deposits can be very hard and very difficult to remove. They can be removed chemically, but the only chemicals I've seen work effectively are pretty dangerous to handle. These deposits make the passages of the toilet smaller, and also plug up the rim jets and siphon jet so that the water doesn't flow into the bowl quickly enough to give a strong flush.
If the flushable product makes it through the toilet, then there is the drainage system to consider. As has been mentioned, these products don't dissolve the way that TP will dissolve. In fact, some of them don't dissolve at all. If your drainage system is constructed correctly, and not afflicted with heavy deposits or roots, usually things work OK. If, however, there are areas of the pipe that do not have sufficient "fall" or downward grade, these items may settle out and cause trouble, particularly in cast iron pipe. I have found that once the flow of water stops, fibrous materials tend to stick to cast iron, or get caught in rough deposits. Now the trouble begins, as the flow in this area will slow, allowing more stuff to settle out, which increases the restriction, and so on until you have a stoppage. Older cast iron systems which have proper fall will often handle these items. Not always.
The ideal situation is to have a new-ish toilet that works well, and properly installed plastic waste/sewer pipe. Out here in California, ABS pipe is the most common, although we're seeing more PVC recently. My house was built circa 1970, and has a 3" ABS sewer. In the 21+ years I've lived here, I haven't had a sewer stoppage. Anything that will go through the toilet will make it to the city sewer, so "flushables" aren't a problem.
