Will Muriatic Acid Damage My Tub

[make_shift]

I have been following the rules for adding muriatic acid to my spa, it seems to be the only thing that works, I can't get the slo'n'low and other stuff to bring the alk down worth a darn.

my question is, will muriatic acid damage my spa, a couple dealers say it 'should' be fine, but I read on the net not to use it in liquid form, so what do you people recommed? i don't want to damage equipment, but the liquid works so well.

please help me figure this out?

[chem geek]

The procedure for lowering the TA is described here and involves adding acid and aerating at a lower pH. Simply adding acid doesn't work as well as it takes longer. The type of acid should not matter so I suspect it's more related to the quantity and strength of the acid being used.

You can use Muriatic Acid but have to be VERY careful with it. I would take a cup or small bucket of spa water and add the acid to it first, mixing it (NOTE: you ALWAYS add acid to water, not the other way around). Then pour this very slowly over a return flow. Do not have the jets on high -- you just want good circulation but not anything that can splash back at you. For safety, you should wear some eye protection (glasses or goggles). Do not pour acid (of any kind) into an intake port (floor drain). You just want it to mix with the bulk of the spa water.

The hardest part is measuring such small amounts of acid. In a 350 gallon spa with a pH of 7.5 and a TA of 120 ppm, for example, it takes only 3 tablespoons of Muriatic Acid (31.45% Hydrochloric Acid) or 8 teaspoons (almost 3 tablespoons) of dry acid (93.2% sodium bisulfate). For easier dosing, you could get the half-strength Muriatic Acid (15-16% Hydrochloric Acid) which would need twice as much, so 6 tablespoons in this case.

Richard

[make_shift]

thanks for that response, I checked out that post, and the post you made about somebody else's readings of ta and ph vs. how many oz of muriatic acid to add...those were all very helpful and do work very well by the way-- but just looking around, some online dealer's and online stores say not to use muriatic acid in the spa because the small volume of water, myn is 1500L, it can damage the spa shell and even equipment, so that's what I want to make sure I don't do. that ph down or slo-n-low don't work for a hill of beans and I don't want to raise my tds, I have to add the liquid stuff for my salt generator yet...so that's what I would like to know based on your experience, will muriatic acid, the way you describe using it, damage the tub?

thanks for your response, you are very helpful by the way, don't know if anybody's mentioned it...

[chem geek]

Thanks for the compliment.

Acid is acid. Well, not exactly as Muriatic Acid results in adding more chloride (salt) while dry acid (sodium bisulfate) results in adding more sulfate, but the point is that if you properly measure the amount of acid then the result on pH in the spa is IDENTICAL. Obviously, if you add too much of ANY acid, you can cause damage and if you add ANY acid improperly all in one place without the pump running or add it with the pump running but directly to the intake (floor drain or to a skimmer in a pool) then of course there will be problems.

Muriatic Acid is denser than water so if you add it quickly in one place not over a return flow then yes, it could settle to the bottom and damage the spa surface. The same can be said for adding Cal-Hypo or bleach or chlorinating liquid to a vinyl pool. You have to make sure that concentrated chemicals get diluted in the main body of water, regardless of the source of chemical. Some chemicals dissolve more readily than others or aren't denser than water so are "safer" if one is irresponsible, but if one is responsible then they can be all equally safe.

If you add some acid to a cup or bucket of spa water and then slowly add it over a return flow to ensure thorough mixing and you add the proper amount, then you won't cause any damage.

Richard

[make_shift]

If you add some acid to a cup or bucket of spa water and then slowly add it over a return flow to ensure thorough mixing and you add the proper amount, then you won't cause any damage.

Richard

perfect thanks

[WaterBeast]

I went through this recently with a 280 gal spa spa that kept creeping up in pH. I started using the liquid pH Down I inherited from the previous house owner and previous spa. This was far too weak and I used a 16 oz bottle or two far too quickly.

Then I ran out, had a high pH, and only had a jug of muriatic acid around. I read up, and went through the nuisance/potential hazard of measuring out small amounts, diluting in spa water, and adding to the spa. It works great, I just hate doling out tiny amounts of muriatic acid from a gallon jug.

I later bought small spa bottles of dry acid pH-, then a 5 lb bucket of pool pH-, which is much more cost-effective. Short news is that the dry acid is plenty strong, cheap in quantity, and not nearly as potentially hazardous as working with muriatic acid. I still dissolve it in a bucket of spa water before adding.

WaterBeast

[Tricia71]

I have a 375 gallon hot tub.  My iron is so high that I can't raise the ph. American sales said to turn off the breaker,  add muriatic acid in the center let it sit for 4 hours before running a clean cycle.  I am not able to completely remove the lid by myself.  Can I take it partially off and the lid still be ok? I have well water and I have used so much of the metal b gone and it isn't working. 

Thank you