A timely question! I just replaced all the valves in a toilet at home last weekend. What fun.
Sloan-type valves are used in the toilets in my office building,
and are in many industrial and educational settings. Most household
toilets instead have a big ceramic tank which can hold a few gallons of
water. Why the difference, you may ask? I like the idea of a simple
spring-loaded valve with lots of flow capacity too, but it won't work
in most houses because of the rest of the house's plumbing.
Most houses have rather thin water pipes connecting from the water
main to the toilets, usually around an inch in diameter. The last
little pipe going to the toilet is usually much smaller, about a
quarter of an inch in diameter or even less. Water will flow rather
slowly through the small pipes, but even if you open the inch-wide pipe
full blast (esp. on the second floor of a home or higher), the flow
rate is usually not astounding. Try it with the bathroom sink faucet.
It's usually not enough to flush stuff down a toilet -- you need a
sudden, strong burst of water or stuff in the toilet will just sit
there after you flush it.
You can get away with the single-valve, no-tank solution if the
plumbing has big pipes everywhere and good pressure (sometimes
supplemented by pumps, especially in tall buildings).
Residential toilets always have a little shut-off valve on the
water supply which is often necessary to prevent flooding in a
bathroom. If you had a big, wide pipe with lots of pressure and a
broken valve, you could be in big trouble very quickly. At least the
traditional solution usually gives you some time to turn the water off
before everything gets wet (or worse).
(republished on 07/31/06)