Looking for Advice on MPS Usage

[tonydatillo]

I've yet to use any MPS in my spa. For the past year it has just been myself or one other person using it a couple times per week. This weekend there will be four people in it for probably a couple of hours and I'm wondering what formula I should use for measuring how much non-chlorine shock to add. Also, should it be added before or after? If after, what difference would it make that I'm using MPS vs. liquid chlorine or bleach?

325 gallon spa

FC - 6
TA - 60
pH - 7.6
CYA - 35
CH - 125

 

[PoolStored]

Check out what @JoyfulNoise has to say here:

Using MPS

Alright, so I'm feeling pretty good about starting up this hot tub, balancing and sanitizing it. My only confusion comes from the use of MPS. I tend to be more of a purist, so MPS confuses me. How necessary is MPS, and if I need it, is it going to mess up other chemicals and/or tests? Thank...

www.troublefreepool.com

Your CYA is 40. Always round up. I would just raise your FC before you get in, and test afterwards and replace more FC if necessary.

 

[tonydatillo]

Ok ... I think I am convinced for this situation. Honestly it seems like trying to use MPS is going to be more trouble than it is worth. Under what circumstance would you use MPS in a spa?

I'll bump the FC to 8 maybe like six hours before anyone gets in? And then if for some reason there is zero free chlorine after everyone is out, I should be able to SLAM to 16 FC based on CYA 40 and get things back under control. Does that seem reasonable?

I've personally never had any issue using my spa with FC at 8-9, but I've read other posts where people won't get in if it is above 6.