If there is a fail safe mechanism for controlling toilet tanks I have not seen it yet. Sometimes the flap for discharging sticks so after flushing the tank doesn’t fill up. Sometimes there is grit in the inlet valve so it doesn’t close. Of course this never happens when you watch it.
The solution could be a small device that is stuck to the outside of the tank and listens for the sound of trickling or rushing water. If the sound continues for more than a normal fill time it indicates a failure and a loud alarm goes off. If the alarm is ignored for more than 5 minutes a back-up valve shuts off the inlet of the tank.
There is some annoyance involved in recovery from the failure. One has to crawl out of bed and go back to quiet that obnoxious alarm or unexpectedly one has a filled bowl but an empty tank so it is impossible to flush. Murphy’s law still applies, but the worst possible scenario is less bad.-- kbecker, Mar 31 2004 How much water does a leaking toilet waste? http://www.sugarlan...for_Water_Leaks.htm"Our experience shows that most leaks occur in the toilet. A leaking toilet tank can waste up to 200 gallons of water per day and cost you 67 cents per day, $20.10 per month! " [bristolz, Oct 04 2004, last modified Oct 21 2004] Conserving Water in the Home http://cea-news.tam...es/CFAM/052998.html"A toilet with a silent leak of one cup of water a minute wastes about 2,700 gallons of water a month...."Silent leaks" are very common and are often missed. " [bristolz, Oct 04 2004, last modified Oct 21 2004] (?) This might solve your problem http://www.flologic.com/products.htmCheaper to fix the toilet, than install this auto shut-off valve [Ling, Oct 04 2004, last modified Oct 21 2004] If you can hear the tank trickling, just whack it. Otherwise, what's the problem? I certainly don't want to be woken by loud alarms in the middle of the night.
Get a plumber if it's that bad. [bristolz: we're talking about drips, not floods. See xRayTed's note below.]-- DrCurry, Mar 31 2004 I'd rather be awoken in the middle of the night if water is being wasted. I wish to be careful about the waste of resources.-- bristolz, Mar 31 2004 Interesting concept that should actually be quite simple to implement. Run the incoming water through a turbine or piston motor which turns one end of a wind-up spring. The other end of the wind-up spring is allowed to free-spin when, and only when, the flushing lever is pulled. If the water runs for too long without the flushing lever being pulled, the spring will wind all the way up and stop the motor from turning, thus restricting the water flow.-- supercat, Apr 01 2004 Toilet tanks are fail-safe. That is to say, when the mechanism fails, the resultant leaking water is sent down the drain rather than onto your floor. This is wasteful, but then so is installing a redundant fail-safe on a device that already has 99.9% uptime.
I would say that the trickling water sound already is the obnoxious alarm, and there is a manual backup valve somewhere that you can turn off when the noise becomes too much.-- xrayTed, Apr 01 2004 // I'd rather be awoken in the middle of the night if water is being wasted. I wish to be careful about the waste of resources. //
This idea doesn't seem like a sensible use of resources, unless you're losing hundreds of gallons down your drain (how much does water cost compared to sensors and alarms?).-- kropotkin, Apr 01 2004 I've heard about valves that close when there is a continuous flow (probably to stop flooding). I'll try to find a link.-- Ling, Apr 01 2004 I was in a hotel room that needed one of these. Because of a trickle leak that I couldn't stop the water would come on every few minutes to top off the tank. Since the water cutoff valve wouldn't turn by hand and I had no tools, I chose to tie the float in the tank in the 'up' position for the night.
I'd rather have a device that would cut off the water and turn on a "fail" light than sound an alarm that would get me out of bed. My commitment to saving 2 or 3 gallons of water is pretty shallow. +-- RooneDitoff, Apr 01 2004 Great link [ling]. That looks useful.-- bristolz, Apr 01 2004 //I was in a hotel room that needed one of these. ...// I was in many hotel rooms like that. At night it drives me nuts when the refill starts every few minuts. Usually I end up shutting off the water at the hand valve (if there is one). For hotels the alarm from the sensor should of course go to the receptionist too.-- kbecker, Apr 01 2004 ////I was in a hotel room that needed one of these. ...// I was in many hotel rooms like that. At night it drives me nuts when the refill starts every few minuts. Usually I end up shutting off the water at the hand valve (if there is one). For hotels the alarm from the sensor should of course go to the receptionist too.//
Actually, for hotels (or come to think of it, for all installations) there might be an easier approach: have a small microprocessor with a moisture sensor that sits in the overflow tube. Normally after a flush, water will flow through the overflow tube for a certain duration and then stop. If the flush valve is leaky, water will periodically flow through the overflow tube, but for a shorter duration than after a flush. It the fill valve is leaky, there will be a continuous very slow trickle through the overflow tube. If the overflow tube feeder hose extends below the waterline and there's no vacuum break, there will either be an alternating slow and rapid flow.
Any of these conditions should be easy to identify, and the electronics should be very simple. Because the electronics don't have to do anything when there's no water, it should be possible for the electronics to run years on a single small battery.-- supercat, Apr 01 2004 random, halfbakery