I watch on a regular basis, enjoy the shows and the tips but...the episode which aired on March 23, 2019 which involved the new low flush toilets and how they are designed and tested, well, crappy is how I would describe the impression it left on me.
The first thing I will say is I'm not that supportive on low flush toilets. I agree there needs to be conservation and limiting waste but I believe the low volume of water is going to create other problems down the line. I don't think the 1.2 gallon flush is sufficient to push wastes down my sewer line to the city main sewer and then be sufficient to move those solids still further down the main sewer to the treatment plant.
This is where I have my problem with the Toilet testing episode. The test done was flushing round poly balls and seeing if they reach the 40 foot mark. Well, I could hear the balls rolling down the pipe so obviously they would roll past 40 feet. The balls would have rolled all the way if no water was involved. Change those poly balls to poly cubes or sponges and see how far they flush down the same pipe. Flush down 3 feet of toilet paper bundled around some peanutbutter and see if it makes it to the 40 foot mark. I seriously can't remember the last time I pooped out perfectly round "..." what ever you want to call it.
I kind of laughed when the designer of the toilet demonstrated the saussage casing test. He said something to the effect of (don't quote me on this) "the requirement is flushing 9 pieces but we test with 12". Of course just flushing through the toilet went fine but lets see how close those saussages rolled down the 40 foot mark on the 4 inch pipe.
The key factor is the water has to push the solids down the pipe. Solids are not going to go freely down any sloped pipe and water will always flow taking the path of least resistance which means a heavy solid will sit there while the water flows around it. What happens to the solid that didn't make it all the way down the pipe? It now becomes a blockage to the next flow of solids because it has rested in place and solidified. According to physics, a body at rest wishes to remain at rest, something like me on the couch Saturday morning watching Ask This Old House.
So if one thinks of what happens further down the pipe or main sewer line you have to ask the question is the reduced water flow going to cause blockages down the line? I also have to aske if they have to add water to the sludge at the sewer treatment plant to work the process there properly?
What should be considered more deeply in the design of the toilet is how the flushing action breaks apart the solids so that we have a sludge flowing down the pipe verses a solid that needs to be pushed down the pipe.
Ok I have ranted enough. Any comments?