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Thanks, but the sides of the tub are currently clean, they are clean because I added the vinegar before I drained it. I just need to figure out how to keep it from returning each time.
I don't agree - acid washing a spa is not as effective as simply lowering the pH and TA over a period of time because the water will clear out the plumbing as well as all nooks and crannies that you can reach by hand. And since you have said that adding vinegar (which lowers the pH and TA) has cleared it out already, I would not do an 'acid wash.' Not to mention what it does to some finishes, like polished stainless steel, chrome, and some headrest pillows. You mentioned that you have added 'lots' of calcium to end a foaming problem... let's look at that. If you have foam, it could be due to things being introduced into your water that cause it to foam. Swimsuits which are laundered are the prime culprit - rinse only but do not wash - and then hair products, lotions, guests who do not own hot tubs, etc. Soft water makes it far worse, so your dealer may have been trying to help by adding calcium to raise the softness level. First - try filling with hard water if you have a choice. By that I mean: if you have been filling your tub with softened water, try filling from another faucet/spigot with hard water. If ALL of your water happens to be very soft, then add only enough calcium to bring the level of hardness up a bit. But you can also fight foam by keeping the sources of foam out of your spa, or by adding a de-foamer. In any case, don't let the pH and TA get above normal and you should not see the calcium come out of solution. That fallout of calcium only happens when the pH and TA climb and stay up.HTH
Thought I'd give you a follow up. Filled tub yesterday morning. At first the ph was 7.9 and the TA 250.Now after adding the dry acid I have a TA of 180, but the ph is still 7.9. I just added 2 more oz of dry acid and will wait till morning to check it again.But, here's the good news, no calcium on walls yet!Thanks for your help!