Thinking about the logic of the intelliph and it makes more sense to me now. Even though I put the acid injection downstream I am still having a situation where acid and hyper chlorinated water are mixing. It’s just now I’m adding acid to chlorine rather than the other way around. With the IPH being upstream and the chlorinator being off while injecting, the slug of acid never encounters the hyper chlorinated water.
Another way around this that I don't think I mentioned, that would eliminate the need to put the IC on a separate schedule and relay:
Schedule the acid injection one minute after the pool circuit goes on. The IC takes about 5 minutes to run its startup and diagnostics rountine. It's not producing chlorine during that period. So the sequence would fire like this:
- Pool circuit goes on and IC powers up, IC goes into "startup" mode
- One minute later, after the flow is well established, the acid pump injects
- One minute later, after the acid is dispensed, the acid pump turns off
- Three minutes later (give or take) the IC starts making chlorine
You could probably dispense acid for up to three minutes, but you'd have to confirm that to make sure it finishes before your IC's "Cell" LED comes on. This is assuming your filter pump is primed and reliably stays that way. Or doesn't take longer than a minute to prime if it happens to lose prime. Injecting the acid one minute after filter pump startup might have its own possible risks. Which is why I included a separate flow switch in my setup.
As Marty points out, this is likely not an issue anyway, but if you're concerned about it, this MO might put your mind at ease. Not to belabor, but this is one of the reasons I went through the lengths I have to keep my IpH/IC combo running as intended, because I didn't want this concern.
I didn't mention this before because you had not yet decided to locate the injector after the IC. You wouldn't want acid injecting in front of the IC during its startup sequence, because one of the things it's doing is measuring salinity. I don't expect a slug of acid passing through during that test would be a good idea.