I'm switching over from tabs to bleach, and I like the idea of automating the bleach delivery. I've read through all of the posts in this section (at least all that looked relevant) and I didn't see anything quite like I'm envisioning. The setup starts as one I read about, where a bunch of inline pool drippers were used to drop the flow rate from a bleach reservoir into the drain plug on the skimmer basket. There were comments suggesting the use of a Hayward valve. All sounds good to me. The suction from the drain basket pulls directly from the bleach reservoir, and the Hayward valve meters the flow down to a very low level so the pump, etc, never sees a high concentration of bleach.
Once the pump shuts off (I run mine six hours/day) even though the flow through the Hayward is slow, unless pressures are exactly balanced water is either going to siphon into bleach container or bleach is going to siphon into the strainer basket. Since the bleach level will fall in the reservoir during normal use, pressures can never remain balanced. Valves which can handle bleach are hard do come by (read very expensive) so that pretty much lets that solution out.
So I was thinking.... I have a planted fish tank where I inject CO2 for the plants. I have a solenoid operated CO2 valve to shut off the flow at night. These are really cheap (just saw one on ebay for $17, shipped). I would install the bleach reservoir slightly higher than the skimmer drain with a T at the top of the reservoir. Connected to one side of the T is a tube running down into the reservoir. Connected to the other side of the T would be a tube run to the Hayward valve (and thence to the skimmer basket). The CO2 valve would be attached to the middle leg of the T several inches above it. When the CO2 valve is open, air can flow in breaking the suction. The bleach tube going down into the reservoir would empty back into the reservoir, of course, and as long as the reservoir is high enough water shouldn't be able to come back from the skimmer to the reservoir (it would just be a gravity thing since there would be no siphon effect). A check valve could be used as long as it could handle undiluted bleach, but I think gravity would be sufficient.
Hopefully I explained what I'm thinking well enough.... When the pump runs, if the valve is open air will be sucked through the CO2 valve into the T, down the tubing to the Hayward valve, and into the bottom of the skimmer basket. No bleach flow. I've got an air leak now at the skimmer basket so I always have bubbles coming out of my jets -- so I know some introduction of some air into the basket is no particular problem. When the CO2 valve closes, bleach will then be sucked out of the reservoir, though the T, and down to the Hayward valve.
If the air flow through the Hayward is small enough, simply opening and closing the CO2 valve while the pump is running would allow a simple control of bleach flow. Obviously this is at the cost of a constant bubble stream any time you are not adding bleach. If the timer on the valve (it is a 110v solenoid, so any simple plug-in wall timer would work) is set to the same times the pump runs this would be minimized to however closely the two timers could be synchronized.
Does this make sense to anybody? The point of all of this, of couse, is to control the flow of bleach with a cheap non-bleach-safe valve. Amount of bleach flow could be adjusted either by lenght of time the valve is open or by the Hayward. If the stream of bubbles is not objectionable, the Hayward could be replaced by a simple valve that you only have to get approximately right because you could fine tune by the length of time the CO2 valve is closed (hence the length of time the bleach is flowing).
thanks for any thoughts!