Jump to content

Chlorine and MPS at same time?


DrewM

Recommended Posts

So I’m new to hot tub and I’m having a hard time with all this. So I’m using Spa fusion sanitizer and spa chlorine free shock treatment. We have had the hot tub 4 days so it is seeing a lot of use. Up to four people at a time(2 adults 2 kids). Currently I’m having a hard time with chlorine. Everything else is spot on. What I’m doing now is adding both chlorine 1.5 teaspoons for 2 person use with 2 teaspoons of mph after use. Should I be adding both at same time? Also next day I read very low chlorine on test strip. Comes up white

Link to comment
Share on other sites

  • 2 weeks later...

First time posting. Been reading these and other forums for the past 3 weeks (as long as I've had my new Bullfrog A7 434gal/1643L with EOS3 ozonator and Wellspring continuous filtration pump and dual-filter system), especially lots of posts by chemgeek, nitro, waterbear, and others. Thanks for your contributions to common learning.

I've read many threads on dichlor/bleach, and couldn't find the answer to the original poster's question. I'm an engineer but not in chemical, so I have to ask:

1) When adding MPS and a chlorine source (my case, 10.3% w/w sodium hypochlorite) at the same time, what happens - do they neutralize each other, if so, at what rate, and what are the resulting compounds? The MPS bottle says safe to swim in after 15 minutes - does that mean safe to add chlorine after 15 minutes?
2) Does MPS oxidize only free chlorine, only combined chlorine, or both? At what rates?

I've read that it takes 2.8275g of 43% MPS to oxidize 1ppm of Combined Chlorine in 100gal water, and that it takes 14.31g of MPS to oxidize 2.2ppm CC in 1000L of water. However, I've read that MPS often shows up in tests as CC, so you would need the proper reagents to eliminate the MPS when testing CC. I've also read that the decomposition rate of MPS at spa temperatures is about 12% per hour, so 90% decomposed after 18 hours, and 95% decomposed after 24 hours, so could also wait out the decomposition before trying to test CC.

Also found that pure MPS is 35.44g per ounce of volume, 6 teaspoons in an ounce volume, 3 tsp in a tablespoon, 2TB in 1oz, therefore you can ballpark 18-21g of 43% MPS in a tablespoon. Nature2 manual requires 1TB/1000L before a soak, and the same after a soak, so for my 1643L, that's 34.5g MPS before a soak, and 34.5g after.

3) Aside from the added expense of using 70g MPS per soak, are there any downsides to dosing this much MPS in addition to maintaining a 3-5ppm FC residual after 24-48hrs? Since MPS slightly lowers pH, this sort of dosage could be desirable since hot tubs tend to have pH creeping up due to aeration.

4) I don't have a Nature2 yet but planning on installing one while also following the dichlor/bleach method to ensure sanitization - any downsides aside from the extra cost of the Nature2?

Per using both AquaChek and Bioguard test strips at the same time, and many days of heavy use over the past 2 weeks, all my numbers are very stable. pH 7.8, TA 90-100, TH 300, CYA 100-150 due to first 2 weeks of heavy dichlor granule dosing (factory-installed biofilms) before I started reading these forums and learned about the dichlor/bleach method.

I have some unknown amount of borates - my dealer supplied the SoftSoak Trio kit. The first of the trio is a water startup packet contains boric acid and sodium sulfate, next trio component is weekly packets which contains MPS, sodium sulfate, and sodium carbonate, last is a water drain packet containing at least sodium sulfate, to be used after 13 weeks of packets run out (which I will use in conjunction with Ahh-some).

Thanks!

Link to comment
Share on other sites

  • 2 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...