Help from other chemical dorks like me, please!

[The Wizard of Spas]

Background: I am a dealer and ardent supporter of sticking to the basics of water chemistry:  Maintain pH, alk and sanitizer levels and generally speaking you'll do fine.  Approach any issues on a per-case basis and don't take advantage of the customer by selling a lot of extras that aren't *needed* unless they insist on it.

Issue: There was a run of bad ozononators a while back that had oil in the ozone line.  Every spa and swim spa in question had their ozone and ozone line replaced, plus we added to each tub several gallons of vinegar to the water to eradicate the fizzy, foamy water (the byproduct of the oil in the line), then drained the tub, cleaned it, refilled and replaced cartridges.  Every spa was fine after that.  Except for one...

This spa continues to show the same issues:  Water is clear, jets turned on, minor foaming and when the jets are turned off it fizzes and takes approx. 5 mins to clear up.  We have repeated the process explained above and the customer has been thoroughly vetted on several occasions to ensure they are not doing anything to discourage the process.  Still no resolution.

Action:  We have gotten some free samples of Aqua Finesse from a rep that was passing through the area (I am thoroughly aware of what that product is, what it does, and what it doesn't do) and have looked up Aqua Finesse threads on this forum before I posted this to get better educated with outside opinions.  I plan on using the free samples given b/c what the heck do I have to lose?  Additionally- I have sent a water sample off to our chemists to see what is going on and to get their feedback. 

Question:  Has anyone had this issue?  If so, any recommendations?  I don't want to continue to lose money via service calls and chems that I am sinking into this customer, who has been a trooper throughout the process.  But as we have a reputation to maintain it has to be done.  I just want to expedite the process. 

Thanks for reading and I look forward to some feedback.

[BullFrogSpasMN]

you mentioned drained/cleaned/refilled twice for this customer...did you attempt to use Ahhsome, System Flush, etc? my instincts would be to add a purge product, drain & clean very thoroughly, replace filters then refill.  If you've already done that twice I would almost have to imagine they might be struggling to maintain the water overall, kind of hard to imagine a little oil would still cause issues after being purged/cleaned/refilled on 2 occasions

[The Wizard of Spas]

Thank you for bringing this up:  I failed to mention that the customer has indeed used a product to cleanse the system on their own and had drained/cleaned/refilled on their own as well.  That is a key piece of information that I stupidly left out.

I have to be missing something, I believe.  I have made sure the customer has told me exactly everything they have done and shown me anything they have used and it all checks out.  I just am at a loss.  Ugh...

[Tman122]

Thank you for bringing this up:  I failed to mention that the customer has indeed used a product to cleanse the system on their own and had drained/cleaned/refilled on their own as well.  That is a key piece of information that I stupidly left out.

I have to be missing something, I believe.  I have made sure the customer has told me exactly everything they have done and shown me anything they have used and it all checks out.  I just am at a loss.  Ugh...

I think ya gotta do the purge yourself. Might be the only way to know for sure.

[Hottubguy]

You said you typically check ph, alk, sanitizer. How about the calcium level in this tub?  With low, super low calcium I've seen foaming before similar to what you are describing