New hot tub was just delivered on Saturday. After a GREAT summer using the TFP method on my pool (after 5 frustrating years of not knowing about this site), I am certainly planning on using BBB on the hot tub as well. My question is, the hot tub installer said that he has seen too many people report heater failure after using Muriatic Acid instead of dry acid for lowering pH. While I find this hard to believe, I don't want to take any chances either. I can certainly understand how too much MA can damage components, and that a hot tub will require very small doses, so perhaps some people have overdosed their hot tub on MA, but are there any thoughts or personal experience from anyone before I give it a try? Thanks!

It's low pH that causes the damage, and dry acid can cause that just as easily as MA. I'm guessing that MA is just easier to overdose than dry acid.

Yup, I agree. There shouldn't be any difference unless there is overdosing. As with all concentrated chemicals that could cause harm, such as chlorine or acid, it should be added slowly over a return flow with the pump running. Don't add it into a skimmer, especially not for acid.

To prevent accidental overdosing, one can add the acid to a bucket of spa water to make sure one doesn't spill too much in and then pour the bucket (after mixing its contents) into the spa with the pump running.

Thanks! I assumed this was the case, it's good to hear it from the experts. I'm looking forward to my TFHT (Trouble Free Hot Tub) to go with my TFP.