Half a croissant, on a plate, with a sign in front of it saying '50c'
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Flush-valve-less toilet tank

No valve--no possibility of leaks.
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A toilet tank (cistern) would be constructed without a valve at the bottom. Rather, the casting would be constructed so as to include a channel down the center which would be somewhat like the overflow pipe, except larger. The side of this channel would have a hole just above the normal waterline in which a large tube would be inserted that would extend from near the bottom of the tank outside the channel, to below the bottom of the hollow part of the tank, inside the channel. The hole around the tube should allow a very small amount of water to flow.

The tank fill mechanism would be of the usual type, adjusted to stop filling slightly below the hole in the pipe.

To flush the toilet, the flush mechanism would push a displacer down into the water. If done reasonably quickly, this would cause the water level to rise to fill the tube and start a siphon which would reasonably quickly drain the tank. Once the tank was empty, the siphon would stop and the fill valve would then refill the tank.

In the event that the flush lever were to get stuck, the fill valve would simply stop filling the tank when the water level reached its normal spot. No more water would then be spent until the lever was released, the water level went down, and the tank refilled. At that point, operating the lever again would re-trigger the siphon.

supercat, Apr 02 2004

How siphon-action toilets work. http://home.howstuffworks.com/toilet.htm
[ato_de, Oct 04 2004]

[link]






       I can't see anything obviously wrong with this idea. Could you explain the part // The hole around the tube should allow a very small amount of water to flow.//?
The displacer would need to move enough water to move the air pocket around the large tube, so that the highest point of the air is below the water level in the tank. Could this be done by pressurising the tank (reducing it's volume), instead of moving the water directly?
Of course, the overflow would need to be modified to let you do it this way.
Having said that, I think the float valve leaks more often.
Ling, Apr 02 2004
  

       //Of course, the overflow would need to be modified to let you do it this way. Having said that, I think the float valve leaks more often.//   

       Pressurizing the tank would seem difficult compared to displacing the requisite amount of water which could be done via large float-like thingie.   

       As for the part about the hole around the tube, I probably over-complicated things there. Try this simplified version for size:   

       The tank is cast with an integral oval-shaped "pipe" [called the overflow pipe] which would be about 2.5" ID and have about 0.75" 'extra' width. This pipe would extend from the inside of the tank, between the normal and super-maximal waterlines, to the exit. Inside this pipe, roughly against an edge of it, would sit a U-shaped piece of plastic tube or pipe (called the siphon tube) with about a 2.5" OD. The siphon tube would extend as noted earlier from the bottom of the tank to a spot in the overflow pipe below the bottom of the tank.   

       Sitting somewhat loosely around the siphon tube would be the "doohickey". This would be an oval-shaped object with an off-center hole through which the siphon tube would pass, and with a small integral pipe (about 4" long and 0.5" OD) passing through it along side the big hole. This short pipe would serve as a 'backup overflow' and also provide a spot for the bowl-fill water hose to go.   

       The design of the doohickey would be such that if the water level in the tank rises quickly, but stays below the top of the backup overflow, then only a little water would be able to flow past it (most would be forced through the siphon tube). If the water level rises slowly, however, it would be able to flow through the doohickey without triggering the siphon flush. If the water level rises above the top of the backup overflow, water could flow down there to avoid spilling out over the edges of the tank.   

       BTW, while the fill valve on a toilet is probably more likely to have severe problems than the flush valve, the flush valve, depending upon the exact design, may be more prone to have minor leaks.
supercat, Apr 02 2004
  

       Heh... and that's the simplified version?
How about: "It's an overflow pipe"?
If you can work out how to retro-fit, then there are plenty of toilets out there that are waiting for a new flusher valve.
Yes, some valves get little bits stuck in them, 'cause they sit at the bottom of the tank.
How about a drawing?
Ling, Apr 02 2004
  

       Sound much more complicated, and therefore more prone to breaking, than a normal toilet. What you are proposing takes a lot more mechanics and force to operate. The flapper valve used to flush is easy to replace if it leaks and would be way cheaper than replacing a bunch of hardware if your design breaks down.
Nitehawk, Apr 02 2004
  

       //Also a syphon just won't do the flushing job unless you have a very very long drop for gravity to do it's work.//
How do you think the water from your toilet tank gets to the pan with a conventional flushing mechanism?
angel, Apr 02 2004
  

       + I like a system with fewer moving parts.   

       The force needed to displace the water is an issue, but I think it could be solved adequately. Here's one possible solution off the top of my head.   

       Have the flush handle attached to a well balanced bucket (maybe shaped more like a trough so it can have more volume without being very tall) that gets filled up when the toilet is filled. Pressing the handle tips the bucket over, dumping it's contents into the tank, starting the siphon as described. As soon as the bucket is empty, it is light enough for the attached counterweight to bring it back to its stable postion for refilling.
scad mientist, Apr 02 2004
  

       Your doohicky sounds like an interesting solution to prevent automatic flushing when there is a slow leak in the filler valve, but I don't think that would actually be a necessary.   

       If the siphon tube is designed properly, a leak will just raise the level slowly and the water will spill through the siphon tube. Assuming the bottom of the siphon tube is slightly above the water level in the toilet, the water will just run down the inside of the siphone tube and air will flow down the refil tube and up the center of the siphone tube. But when the water level rises suddenly, the siphone tube will be flooded rapidly, so air can't bubble back fast enough to break the siphon, causing the toilet to flush.
scad mientist, Apr 02 2004
  

       Looks like the flushing system has come full circle: if we have a big enough bucket, there is no need for a siphon.
In some parts of Asia, they do exactly that. They dip a large plastic dish into a tank of water, and then throw the water down the bowl...
It can only go wrong if you miss the bowl.
Ling, Apr 03 2004
  

       Baked in the UK... pretty much every toilet here flushes using a siphon action. The flush handle lifts a large diameter (say, 10cm) diaphram which doubles as a one way valve (up only) from the bottom of the tank. This lifts water into an inverted U-shape, the apex of which is above the tank's water line, and out through the pipe connected to the other end of the U. When the handle is released, the diaphram (which has distorted upward letting the water rush past) is weighted so it can drop back down to the bottom. Some toilets also use it as a valve to save the amount of water used (generally the whole tank is used every flush). This means the toilet never suffers from flush leakage, but means that if the tank is not full enough the mechanism cannot lift enough water to start the siphon action, resulting in a rather frustrating 'cough, gurgle' as the handle moves pretty freely. Once the tank has filled, the handle is harder to move (you're lifting a litre or so of water) but very satifying to operate. :-)   

       Before I went to other countries with flush toilets I assumed this was how they all operated.
Jim'll Break It, Apr 03 2004
  

       Jim thanx for that i am also English and was wondering what they where on about.
engineer1, Apr 03 2004
  

       Is that how the pull-chain tanks work? I'd never looked inside one because they were always taller than me, but I'd thought they had something like the flush-valve mechanism seen on U.S. toilets today.   

       Certainly the pull-chain tanks at my grandmother's house never wanted for flushing power. The toilets were replaced some years ago because they must have used some absurdly huge amount of water per flush, but when the chain was pulled those things would unleash a tempest in the bowl.
supercat, Apr 03 2004
  

       [supercat] maybe it's the increased height from the tank to the bowl too.   

       Gosh - never thought annoying parents by dismantling toilet cisterns while bored as a kid would become useful in later life, but I guess that's the engineer in me...
Jim'll Break It, Apr 04 2004
  
      
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