The Straight Poop

A reader asked recently about dual-flush retrofits for existing toilets. These are devices that give you choice of a half flush for pee and a whole flush for the poo. She wanted to know what I thought she should do; Replace old toilets or install the retrofits. She pointed out that retrofits were cheaper and she wouldn't be adding more old fixtures to the land fill. Point well taken about the toilets in the landfill, but I still had to recommended that she replace high water using toilets with new ultra-low flow toilets or High Efficiency Toilets. I came to this conclusion after reading a cautionary memo from John Koeller, the guru of toilet testing. He warns that these devices must be approached with much caution. (Sounds scary doesn't it?) More about him later.

John says that even though manufacturers claim astronomical water savings for these dual flush retrofits, there have been no real-world studies that support these savings. His concerns are:

1. Changing in the full flush characteristics of the toilet fixture can adversely affect flush performance. This will lead to double flushing to get the waste down.
2. The reduced flush is particularly vulnerable to unsatisfactory performance. If it doesn't appear that the liquid has disappeared, addition flushes will ultimately occur.
3. Most of the flush valves are adjustable and allow the owner to adjust the flush way above the original flow rate.
4. Installation requires the owner to disassemble the tank from the bowl, remove the flush valve and replace and adjust the new valve. All kinds of potential for problems there. Replacement will also void the warranty.

Picky stuff? Well John Koeller knows his poop - literally. People were upset about having to reflush the 1.6 gallon flush toilets that they were required to install. John responded to the problem by conducting the MaP test, Maximum Performance test of popular models of toilets. This test resulted in a list of toilets guaranteed to do the job in one flush.

Did you know that the maximum average fecal size of an adult male is 250g? John used this data to create a soybean test medium to be extruded through a tube resulting in a cylindrical specimen 4 inches long. This is plopped from a scientifically specified height into the toilet being tested. A prescribed amount of toilet paper is added and flushed. It better all go down or else the toilet won't make the cut. This is fascinating research. I've met John in person and he really seems like a normal guy.

So. . .take it from the expert. You spend a lot of time flushing that fixture. It makes sense to choose the option that is stands up to "real world" demands.