Chlorine Or Mps: Which Is A Better Oxidizer?

[lagreca]

A friend recently told me that Chlorine is not as good an oxidizer as using MPS.

I'm following the dichlor/bleach method, but have NOT used any MPS since switching to bleach.

I'm not real clear on if or when I should even use MPS? I thought if I shock with bleach after a high bathing load, that would oxidize the waste.

Does one oxidize faster?

When dosing by the rule of thumb, 5 fl oz 6% bleach per person per bathing hour, how long should it take to oxidize the bather waste? 30 minutes, 1 hour, several hours, 24 hours?

[chem geek]

That information is simply not true. MPS does not oxidize ammonia while chlorine oxidizes it relatively quickly. MPS oxidizes some chemicals that chlorine does not and vice versa, but generally speaking chlorine alone in a spa will handle bather waste well. You can always use some MPS if you want to, but it's more expensive for equivalent FC oxidizing amount. Every person-hour of soaking in a hot (104ºF) spa with no ozonator requires roughly 3-1/2 teaspoons Dichlor or 5 fluid ounces of 6% bleach (3-1/2 fluid ounces of 8.25% bleach) or 7 teaspoons of non-chlorine shock (43% MPS).

The oxidation of bather waste varies where some chemicals such as ammonia are oxidized quickly at hot spa temperatures, usually within one hour, while others such as urea take longer taking 8-12 hours or longer, but usually much is oxidized within 24 hours. For chemicals slower to oxidize, they build up to some steady-state as a function of the bather load, but are usually innocuous -- at typical residential spa concentrations chlorourea isn't volatile and is not irritating, for example.

[lagreca]

Would best practice be to use MPS once a week, few weeks, or month to oxidize whatever the bleach was unable to? Or is MPS simply not necessary at all?

[chem geek]

MPS is optional, not necessary. You can see how you do without it. If you have any issues such as cloudiness or a chloramine smell, then you can try using some and see if it makes any difference. Most people using the Dichlor-then-bleach method don't use any other oxidizer.

[Spanky]

One reason MPS is recommended by dealers is that they also recommend dichlor ONLY (no bleach). This results in high CYA which severely reduces chlorine effectiveness. That's why they believe MPS is more effective. The're baising their opinion on experience with "their" system and either don't know or refuse to accept that high CYA is the culprit