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Ask 'Dr. Spa' Q & A Message Board

Ask 'Dr. Spa' Q & A Message Board archives

Re: Epsom Salts
In Response To: Re: Epsom Salts ()

Why do I think it will cause corrosion? Because I've been fixing hot tubs for 22 years and I have seen the damage it has wrought (not to mention I've made a bundle repairing the damage). Balancing the water of the hot tub usually involves removing minerals at the outset, not trying to add more. If you want to soak in Epsom Salt, do it in your regular bathtub, not in a hot tub where you will damage the components and void your warranty. If you doubt me, call the factory that you will be purchasing a tub from and ask them if you can safely add Epsom Salt to the tub. You will get an emphatic NO.

Interestingly enough, you are on the proper trail with the chemical formulae, but are misinterpreting what will happen. The Magnesium is going to dramatically increase water hardness. Furthermore, pH up or pH down are used in small quantities to adjust the pH, not the large quantities of Epsom Salt that would be used. Therefore, the adverse chemicals introduced via pH up or pH down are minimal and easily diluted. The amounts of these minerals and chemicals would be much greater in an Epsom Salt bath, resulting in more dramatic adverse reactions to the silicone seal of the jets and the various metal components of the tub (ie, heater element, pump seals, etc.).

By adding these additional chemicals, you are also producing more by-products of chemical interactions. One major interaction will be a significant increase in the production of chlorides. Chlorides are corrosive to most metals. In addition, salt compounds tend to increase the rate of galvanic corrosion in a hot tub (in this case, dramatically so around the heater).


: John,

: Pardon me if this reasoning seems wrong. I am
: in the process of buying my first Hot Tub
: and would really like it to resemble a
: Mineral Spa. So I have been trying to decide
: if there is a
: problem with adding Epsom Salt (MgSO4) to a hot
: tub.

: Why do you think it will cause corrosion?

: The cation for Epsom salt: SO4 is in common use
: in the SPA chemical: pH down (Na2SO4)

: The Mg+2 ion is one of the two most common
: cause of hard water:MgCO3 CaCO3. So it is
: most likely already present in everyones
: water.

: The SPA chemical: pH Up (NA2CO3) adds in the
: other cation.

: It seems to me that the main result of adding
: Epsom salt to SPA water is to raise the Mg+2
: ion concentration making water which may
: already be hard a little harder. This could
: pontentially cause Magnesium Oxide ( Mg[OH]2
: ) to precipatate out since it has a very low
: solubility.

: Has anyone added Epsom Salt to a hot tub? If so
: what was the result?

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