Confused...is My Dealer Spa Tech Correct?

[G-Dub]

I have a 350 gallon Marquis tub with ozonator, purchased 2012. Recently my tub was overheating and shutting down in an overheated state. Had tech out - diagnosed stuck relay, pump was running nonstop on low speed and in the summer/fall heat causing it to overheat. Replaced control board and all is good now.

While the tech was here, we discussed hot tub chemistry. I have followed the directions on this forum and found it so helpful. After draining I fill my tub using a hose end filter. Then adjust chemistry, I have found my filtered tap water to have a hardness of about 20, pH of 8.0 and TA of about 120. I add calcium to a hardness of 150, then do serial dosing of dry acid to drop pH to 7.0, followed by aeration, until my TA is about 50. This is the sweet spot for me, keeping the pH about 7.6. I then add Gentle Spa at 50ppm, according to the bottle.

I then add sodium bromide bank according to the bottle, and have then shocked with chlorine bleach. When the level drops below 10 I add the floater with bromine tablets, and shoot for a level of 3 to 4. I use chlorine beach to shock after we use the tub, using 8.5% bleach I have figured 1oz = about 2ppm, and usually add about 4ppm/person/hour after use. This means I often add 4-8 oz of bleach (we tend to do long soaks).

I thought I had this all figured out, and was working well. But I have been having a few symptoms of late that we discussed, the tech blamed all of it on using the chlorine as a shock. He thought that was a terrible idea, and was causing damage to the tub. His recommendation was switching to MPS as a non-chlorine shock instead.

Here are my symptoms:

--occasionally white swirl on surface of water (not completely covering surface) - he said this was indicative of too much sanitzer

--raised bumps on inner lining of cover - he said this again was too much sanitizer

--coughing when breathing in vapor above water, especially just after opening cover

--jets wearing out - and no longer staying in their place. Several jets I had to screw closed to keep them from shooting out when the jets were turned out. Examining these jets there is white gritty material around the surface of the jet - which the tech said was breakdown from the chlorine.

I don't believe the pH or TA ever got too much out of whack, but suppose its possible. Also, I tend to put the bleach in the tub after we get out, and when its damn cold out I put the bleach in and then immediately close the cover and we go inside.

Also was warned by the tech about the possible damage to seals and pumps from using chlorine.

Thoughts? I thought I had this figured out. But, I must admit I am concerned about the symptoms listed above (particularly the coughing and jets wearing out). Other causes for those symptoms if its not from the chlorine bleach?

By the way, I use a Taylor 2106 test kit, reasonably confident in accurate test results.

Thanks!

[chem geek]

It's up to you if you want to use more expensive MPS as an oxidizer to activate bromide to bromine. So long as you had a bromide bank, the chlorine lasts only briefly since in minutes the chlorine gets used up converting bromide to bromine.

As for a white swirl, that does not come from too much sanitizer. If you used the wrong kind of bleach -- splash-less or outdoor -- then those have thickeners in them that can cause foaming. You should use plain regular unscented bleach.

As for the other symptoms, if you are keeping your bromine level too high then yes that can be a problem, but changing to MPS won't change that for maintenance bromine levels though can help for short-term dosing after a soak.

You can certainly switch to using MPS and see if anything changes, but I bet it will only change if you don't go as high in bromine level. Your 3-4 isn't horribly high though (you could target 2-3 instead, if you like), but your going up to 10 after each soak is high until the bather load gets oxidized. To the extent that the MPS will oxidize some of the bather waste and is slower to raise the bromine level, it may help.

If you switch, let us know if you see any difference. That would be one reason in bromine spas to use MPS, particularly if one has heavy bather loads. It lets one not peak the bromine level as high after each soak. Unlike chlorine spas that have CYA in the water (from using Dichlor) to moderate the chlorine strength, bromine has no chemical in the water moderating its strength.