Shocking with Chlorine

buckwheat12n

Member
Jan 26, 2021
6
Ohio
I'm in the process of trying to shock my spa (325 gallons) with liquid chlorine 7.5%. I had been using MPS but get an allergic reaction when using it so I thought I'd try switching to liquid chlorine. I've tried, quite a few times now, adding 6-8 oz of chlorine to get the water up to shock level. I've been waiting about 15-30 minutes or so to test and the highest level of chlorine I'm getting up to is roughly 4 ppm. Based on a chlorine calculator I referenced it should be around 12 ppm with that amount of chlorine. Is there something I'm missing here? I've tried a couple different bottles of chlorine thinking maybe the chlorine was the problem.
 
Last edited:

buckwheat12n

Member
Jan 26, 2021
6
Ohio
I'm using a Taylor-k2006 test kit. The date on the bottle is kind of smudged so I can't tell the date from the side. Maybe I'll grab another bottle and make sure to double check the date on it before hand.
 

CuckooChris

Well-known member
Sep 14, 2016
62
Coplay, PA
If I understand it right, MPS isn't a sanitizer. It just helps break down stuff that has been killed by chlorine. If that's the case, you may not be having a reaction to it, you're getting hot tub rash because you're sitting in a tub full of bacteria. I'm no expert, but many on here are and will correct me if I'm wrong. If it was me, I wouldn't use the tub until I purged it with Ahhsome and refilled it.
 
  • Like
Reactions: Mdragger88

buckwheat12n

Member
Jan 26, 2021
6
Ohio
This is a new tub. I just refilled the water because I thought the same thing but that didn't help. I use the @ease Frog system along with MPS for sanitizing. I pretty much have had the issue from the get go and it seems to worsen after "shocking" with MPS.
 

CuckooChris

Well-known member
Sep 14, 2016
62
Coplay, PA
This is a new tub. I just refilled the water because I thought the same thing but that didn't help. I use the @ease Frog system along with MPS for sanitizing. I pretty much have had the issue from the get go and it seems to worsen after "shocking" with MPS.

Ah, ok, didn't know about the Frog System, which I know nothing about. I'm a straight chlorine guy. Did you purge the tub with Ahhsome when you first got it installed? There are multiple posts from people about how dirty new tubs are and why you should always purge first. Do you have a CC reading? Should be able to do that with the K2006.
 
  • Like
Reactions: Mdragger88

buckwheat12n

Member
Jan 26, 2021
6
Ohio
I bought a new container of bleach rated at 7.5% with a date of 12/15/20. I poured 8 oz in the hot tub and the FC went to 4.5 ppm where it should have been sitting at around 12 ppm. For the CC reading I did some research and found the below at the Taylor website, all of the other levels (PH, Alkalinity, Calcium etc...) are where they should be for the Frog system.

"Incorrectly referred to as “non-chlorine shock” (it is actually a non-chlorine “oxidizer”), although shocking with MPS has been a welcomed innovation, testing pool/spa water that contains MPS with a standard DPD chlorine test has not been as satisfactory. MPS oxidizes the DPD #3 reagent (used to measure total chlorine) but not the DPD #1 and #2 reagents (used to measure free chlorine). The endpoint of the test is a dark red, which falsely indicates the treatment has increased the chloramine level, when in reality it is the residual MPS that is being read."

I found the above to be true in my case.
 
Last edited:

Enjoying this content?

Support TFP with a donation.

Give Support

jimmythegreek

TFP Expert
Bronze Supporter
In The Industry
Aug 10, 2017
3,561
Morris Cnty NJ
I'm not familiar with the frog system either. The best way is to treat it like a small pool. Just have to understand the bathers load is extreme amd dose it as such.
 

Mdragger88

Bronze Supporter
Jun 1, 2018
1,958
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
I am concerned that your skin reaction & high chlorine demand is due to something funky in the water. Just replacing the water won’t rid u of biofilms which protect nasty bacteria 🦠. Only an Ahhsome purge will do that. As stated above even brand new tubs can have this problem due to the fact they are water tested at the factory & then things can sit in the plumbing & grow until it gets to u. Then as soon as u start using the tub you introduce more organics. The frog isn’t all it’s cracked up to be either so if u are going to continue using it I would suggest you still follow this guide primarily & only count on it as a supplement 👇
It is also conveniently pinned 📌 to the top of this forum.
 
  • Like
Reactions: CuckooChris

plove42a

New member
Mar 2, 2019
4
Kansas
I had an allergic reaction to MPS also, and that's how I ended up here with the Dichlor/Bleach method, so you're not alone. Affected me alone, no one else in my family.

Even if your spa is new, I'd recommend a flush with Ahhsome, and then the dichlor/bleach method. It's very easy to monitor the health of your spa by monitoring your Chlorine Demand.
 
Thread Status
Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.