I do not know any reason a Toto would respond any different than any other low flow toilet with cast iron pipes. If the pipes are in good shape and installed with the proper slope there should be no problem. My personal Carlyle's are installed with cast iron pipes (house built in 69) and we have no problems. GREAT toilet!

: We need to replace toilets in our 1958 house. I was almost set on the Ultramax, or the Carlyle, until I read the article from Fine Homebuilding. We have the cast-iron pipes, so are these not a good idea for here? Would holding the lever down longer make the difference?