Loosely parphrasing the overlooked admendent, the Tenth amdendment, anything not specifically granted in the Constitution is reserved for the people or the states. So to the earlier question about what part of the Constitiution is being violated, it’s the 10th admendment. Other than that overworked and beat to a pulp “regulating commerce” clause show me where Congress has been granted the power to regulate my toliet flushing.
Oft-used or not, the Commerce power is still a pretty good hook for most legislation enacted by Congress. I would also think that sewage issues can effect the quality of the nation’s “navigable waterways.” That’s assuming, of course, that the current understanding of the federal government as having no “general police power” is correct, by no means a clear prospect.
And of course, there are no concerns at all of this kind if a state or local government wants to regulate toilet capacity.
Um, excuse me, but can someone please cite the USCode or the CFR for either statute or regulation passed by the federal government that bans the sale of high-flow toilets? I don’t think this is something done at the federal level folks, but I could be wrong. Provide a cite and text, and we can be sure. 
DSY, I searched the USC under the Titles for Conservation, Commerce and Trade, Public Buildings, Property and Works, The Public Health and Welfare, and even Navigation and Navigable Waters, and could find nothing at all related to toilet flow rates. Ditto for OSHA/CFR.
Couldn’t find anything under the ORC for the State of Ohio, either.
You couldn’t find it, pl, because you were unwilling to get into the toilet. From http://www.americanstandard-us.com/scripts ,
I subsequently found that the ’92 Act is known as PL 102-486.
So who can share the best way to look through the US Code on-line?
Livin’ on Tums, Vitamin E and Rogaine
Oh, and I just can’t resist sharing this additional gem from the folks at American Standard
So you really do learn something new every day.
And also from your site:
So we must require all federal political candidates to state for the record whether they support repealing PL 102-486, ie, the how do they stand on the low-flow toilet issue. Let’s see Bush, Gore, Bradley et al respond to that one.
Wow! Talk about things you never knew you never knew!
http://law2.house.gov/usc.htm#search
Use that location for US Code searches, then expect to spend a LOT of time snapping up red herring. 
What you will find is that toilet flows are regulated under Title 42 USC Section 6295. This section is located under the title on Public Health and Welfare, Chapter 77: Energy Conservation, Subchapter III: Improving Energy Efficiency, Part A: Energy Conservation Program for Consumer Products Other Than Vehicles. And BOY do they do some regulating! Everything from lights to bathroom fixtures to appliances, etc.
I guess I thought that all this law did was force manufacturers to label appliances and the like as to energy efficiency, but the labelling standards (Section 6294) are only a very small part of Part A of Subchapter III. Originally made law in 1975 (PL 94-163, the Energy Policy and Conservation Act), it has been amended numerous times, most recently in 1992 under the now infamous 1992 PL 102-486.
What, then, does this fall under for Congressional power to act? Presumably, all this falls under the long infamous ability of Congress “To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes;” under Article I, Section 8 (the Interstate Commerce Clause).
Your tax dollars and votes at work, folks!