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Q & A: Toilet valves

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Most recent answer: 10/22/2007
Q:
Since a toilette valve (such as Sloan Valve) does not accumulate water (due to its small size) and does not amplify pressure (no external source of power), therefor, it must just be a heavy duty spring-loaded valve that, simply, controls flush duration -- i.e., the volume and the pressure is due entirely to the water in the upstream pipes of city’s pipe system. Why then, some owners go through the expense of installing old-fashioned-type flushing systems which have many moving parts and, hence, subject to rust and breakage?
- Mehran
Lisle, Illinois
A:
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).

Tom

(published on 10/22/2007)

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