This is an add-on to the “quick and easy chlorinator”(QAEC) that I posted. Basically, it harnesses the gravity drop a bit more effectively, allowing the chlorination to be more accurate and reliable, all the while keeping everything pretty cheap, and, I think, reliable and low maintenance. You might also want to add a level sensor to the solution tank, so the PLC knows when the tank is empty. You can get these cool capacitive sensors also known as “capacitive limit switches” that can sense through the wall of the chlorine tank, without any concern that the material might get attacked by the chlorine.
Basically, the different levels in involved here are important. First, suppose it is empty. The water slowly flows into chamber 1. When this reaches a level higher than the output tube attached to the chamber, water starts to drip into chamber 2. The purple line represents the feedback tube for the QAEC. The bluish line represents the chlorine solution output line. As the water level starts to rise in chamber 2, chlorine solution is dripped into chamber 1 at just the right rate (which depends on the diameter of the feedback tube and concentration of the solution).
When the water level in chamber 2 reaches the float valve shown, the valve opens. Water starts to flow out of chamber 1 fast. It gets above the highest level in the outflow tube, and then water starts to siphon out from that point onwards. It continues to siphon out until the water level in chamber 2 is below the end of the outflow tube’s inlet.
In other words, its like a toilet flushing.
The float valve mechanism even, is sort of optional.
You could make it so that when water reaches a level higher than the highest level in the outflow tube, the tubes are the right diameter so that the water starts to siphon out, like a flushing toilet. But the tubes can’t be too wide, or the water might run down the tubes along the wall rather than siphoning. That would be total malfunction…. hm. I’m not entirely sure how to be sure that could never happen, but the float valve could help. I don’t know exactly how the physics go here – what determines whether the water flows down the side of the tube or goes down in a sort of plug of water, allowing siphon action?
I think it is a matter of the adhesion of the water to the wall, the hydrophilicity or hydrophobicity of the material it’s made from, vs. the water’s surface tension.
In that case, a teflon tube should work fine to ensure the plug-flow. Alternatively, you could use a valve that dumped the water really fast, or you could have a simple mechanism to tip the chamber 1 over to dump the water into chamber 2 when the water level was high enough.
Another way to do the rising and falling that doesn’t depend on siphoning, would be a float valve like in the toilet tank. This is a valve seat with a float attached to it. When it is surrounded by air the valve is closed. As it is submersed in water, the weight of the water keeps it closed, but there is a force acting to try to open it, from the float. When the valve does open (by operating the flush handle), the pressure difference holding it shut is gone, and the flapper valve stays open because of the float’s buoyancy, until the tank is empty. You just need a way to open the valve when the water gets high enough, this could be done with a 2 level float valve, which sort of snaps up when the force on it is high enough, and snaps back down again when the water level drops.
Chamber 3 just mixes the water a bit and interfaces the outflow tube to the beginning of the contact tank. The volume of the contact tank must be larger than the volume of water that comes out at each flush, and also large enough to store the water for long enough to do the disinfecting, given the flow rate.
If it stops working, you will know, though, because you can smell the chlorine in the water. You could see the solution dripping into chamber 1 as it operates, too. The worst case would probably be that it operated intermittently, merely under chlorinating the water, but I think that’s pretty unlikely. Also this could be detected using chlorine test strips, which are probably a good idea to have around anyway.