Had Chloramines. Added oxidizer now fc is high

mrdorkdar

Well-known member
Nov 23, 2017
63
Lake Forest, CA
So I have an intex saltwater spa. Had 1.5 fc and 1ppm of combined chlorine. I used the Taylor 2006 kit which measures both. Also have roughly cya of 20. So I added a lot of chlorine free oxidizer. Prob 30 ounces instead of the 2-4 the bottle said because I wanted to break the combined chlorine. The guy at leslies said you technically can’t add too much oxidizer. But today when I checked it, my free chlorine was like at 20ppm! Why would a chlorine free oxidizer shoot up my chlorine level? The guy at leslies even said the maximum level the chlorine would go up to would be whatever the test kit said the combined level was which was 1.5 because that is in essence all the chlorine that is in the spa. So what am I missing here?!
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,930
San Dimas, CA (LA County)

mrdorkdar

Well-known member
Nov 23, 2017
63
Lake Forest, CA
https://www.lesliespool.com/blog/pool-care/pool-chemicals/choosing-the-right-pool-shock/

The main disadvantage to using Fresh N’ Clear compared to a chlorinated shock is that chlorine-free shock does not kill bacteria or other microorganisms that may be present in the pool. These can only be killed with chlorine. Fresh N’ Clear relies on using oxygen to free up CAC, which can then be used to target the bacteria and microorganisms. Chlorine-free shock needs to be used in unison with a water sanitizer like chlorine tablets.”

So this is just one big lie you’re saying? Kind of hard to find that to be true.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,238
Tucson, AZ
So you took the advice of a pool store employee (whom we generally do not trust as few actually have pools) and then added 10x the recommended amount and now are wondering why you have issues ?!?

Simple. Avoid the pool store and actually learn about the chemistry and a proper way to maintain a pool.
 

jseyfert3

Bronze Supporter
Oct 20, 2017
963
South-Central WI
I added 10x the amount to hit chlorine breakdown point. Isn’t that what literally every website says to do to get rid of combined chlorine?
No, that's 10x ppm of FC more than your CC, not non-chlorine product. I.e. you had 1 ppm CC, you bring your FC up to 10 ppm.

How big is your spa? Indoors or outdoors? How much CYA do you have? Are you trying to follow the advice in the spa sticky or are you following pool store advise?

MPS is not needed. You can do it 100% on chlorine. If MPS is used, it should be small amounts, not some huge dump of it. MPS falsely reports as CC on testing, haven't heard of it messing up FC test but at the quantities you used, who knows what it will do?

For an outdoor spa, getting rid of CCs is as easy as getting your chlorine up to the proper level for your CYA and leaving the cover off to let some sun in for a few hours.
 

Akathisia

Gold Supporter
LifeTime Supporter
Jul 6, 2015
135
Davis, CA
...follow the advice in the spa sticky...
3 years ago I stumbled across this forum when we bought a house with a spa and a pool. Before that I knew nothing about pools/spas. I've followed the spa sticky faithfully along with Ahh-Some during each drain and refill and have never had any issues. I always use bleach because it's so easy and cheap. It is truly trouble free.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,238
Tucson, AZ
Breakpoint chlorine level is nonsense. And you will not find it taught here because not all CC are created equal ;)

Just follow the SLAM Process process when there is an issue.
 

setsailsoon

Gold Supporter
LifeTime Supporter
TFP Guide
Oct 25, 2015
3,381
Stuart/FL
MR,

Getting back to your original question, I think the oxidizer is interfering with your chlorine test reagents. I've never used oxidizers but looked into them before I took over my pool from the pool maintenance company. I recall there are special reagents you can get that don't have this problem... I'm no expert on this topic but I know the chemistry experts that know all about this are on this forum, maybe one will chime in. AFs I recall there are a lot of articles that indicate oxidizers are of no real benefit unless you have an indoor pool. UV light and FC do a great job without the complications you're experiencing, relatively high cost, and adding sulfates unnecessarily.

I evaluated a lot of options for pool care before I took over since I had only one shot. If it didn't work my wife would make me slither back to the pool maintenance company. Now 3 years later with the best pool in the neighborhood, about $10/Mo in chemicals she wouldn't ever do it any other way. I highly recommend you read through the material and consider switching to TFP methodology

One last thing. Leslie's can be a great resource, it's by far the cheapest source of liquid chlorine for me and the person we normally deal with is fantastic. He' very supportive of people that choose TFP method. But I've also run into several that were dumb as a bag of hammers and people just thought they knew what they must know since they worked a Leslies. I've also had Leslie's people tell me my methodology won't work (I've been doing it with great success for 3 years!) and actually tell people in the store to "never by liquid chlorine, you're only buying water". So that's where a lot of the animosity comes from towards Leslie's but they do have some dedicated customer focused people too.

I hope this helps.

Chris
 

jseyfert3

Bronze Supporter
Oct 20, 2017
963
South-Central WI
How can you say that? Even the slam shock amounts for my spa are 24ppm...that is basically 10 times the usual amount!
Okay, I did a search, found a post by chem geek, and as usual, learned a lot. The post is here, but I'll try to summarize it. Essentially, there's nothing special about getting rid of CC's. Any amount of FC will work on breaking down CC's that can be broken down by chlorine. So simply testing, adding, and maintaining your FC level based on your CYA level will break down and remove CC's.

The 10x rule comes about from trying to figure out how much total chlorine needed to be added to break down CC's. Two issues with this: First, it's based on breaking down ammonia, which isn't CC's, so the ratios are off for typical the typical CC. Secondly, it's how much is total is needed to break it down. If you constantly test and maintain your FC level, the CC's will get broken down. You don't have to maintain a certain ratio of FC to CC.

I'll add in that some CC's are resistant to breaking down from chlorine. The answer is simple, UV. Just open your spa to the sun for an hour or two.

How can you say that? Even the slam shock amounts for my spa are 24ppm...that is basically 10 times the usual amount!
Not quite. Again, you have to refer to the chlorine/CYA chart. This isn't something "the industry" has got on board with yet, but it's very well proven here at TFP. A shock/SLAM level of 24 would be for a pool with a CYA of 60 ppm. For the same pool, the minimum FC level is 5 ppm, and the target is 7-9 ppm. So that's just a factor of 3 higher than normal based on target FC levels, and still only a factor of 5 higher than the minimum FC level. You might have noticed all the values are dependent on CYA level, which is why I keep bugging you to post your CYA level.

If you think those values are crazy, you are new to TFP, so welcome! Please read this guide on using chlorine in a spa. You'll need a good test kit to properly maintain your spa, strips are proven to be very inaccurate. If you have other questions, please, feel free to ask! However, do note that to give good, accurate advise for you, we will need a complete set of current test results (FC, CC, CYA, TA, CH), we'll need to know how you tested it, and how big your spa is. We really do want to help you, but we need you to help us help you, otherwise we are just guessing.

We recommend that you add a signature, so that your spa size, test kit, and sanitizing method are always visible whenever you post. Be sure to click the "Show your signature" checkbox on the reply page so it shows up.

Perhaps. You certainly need that if you continue to use MPS. As I said before though, there is zero need to use MPS if you don't want to. Chlorine (with perhaps a little help from UV) will do all you need. But you do need to do just a bit of reading to learn how to properly use it, as must industry advise only works for a while as they don't understand the details like we do here at TFP.
 

JamesW

TFP Expert
Mar 2, 2011
20,685
The interference with CC is well known.

The fc reaction is not expected under most circumstances.

Monopersulfate is an oxidizer. It can react with the fas titrating reagent R-0871, which is a reducing agent. It adds to the total drop count in the fc test. The large amount used probably interfered with the fc test.

We really don't use monopersulfate with the TFP method, so it's really not discussed much.

Monopersulfate can oxidize halides to halogen. Halides are iodide, bromide and chloride. Monopersulfate can oxidize each into its respective halogen, iodine, bromine and chlorine.

The reason that monopersulfate interferes with the CC test is that it easily oxidizes the iodide in reagent R-0003 into iodine which reacts with the dye in the fas-dpd powder.

Monopersulfate will also oxidize bromide to bromine. If your hot tub contains bromide, that can explain the big increase in measured fc.

Monopersulfate can oxidize chloride to chlorine, but it's usually not a big enough difference to measure. Since you used so much monopersulfate, it might have been enough to cause the chlorine increase.

The amount of total chlorine needed to oxidize all CC is a total chlorine that is 1.5 times the CC. For example, a CC of 2 requires 1 ppm fc because 2 x 1.5 = 3 = 2 +1.

Chlorine takes three electrons from the nitrogen in ammonia. Since each chlorine atom takes 2 electrons, it takes 1.5 chlorine atoms to oxidize 1 nitrogen atom.

When measuring ammonia in units of nitrogen, the correct amount of total chlorine is 7.5 x the nitrogen. For example, 1 ppm ammonia in nitrogen units requires 7.5 ppm total chlorine (fc + cc). 1 x 7.5 = 7.5 = fc + cc.

CC is measured in units of chlorine gas. So, ammonia ppm measured as CC is reported in units of chlorine gas.

Ammonia measured in units of nitrogen will be 1/5th the weight of ammonia measured in units of chlorine gas because chlorine gas is 5 times heavier than nitrogen.

5 x 1.5 = 7.5. So, the 1.5 x or the 7.5 x is the same amount, just using different ways to measure the amount of ammonia. Ammonia in pools is usually measured as CC and reported in units of chlorine gas. Ammonia measured by an ammonia test kit is usually reported in units of ammonia-nitrogen.

The 10x rule came from the nitrogen rule of 7.5 x plus a little bit extra to speed up the reaction.

DuPont Oxone Monopersulfate Compound Technical Information.

The active ingredient of Oxone® is potassium peroxymonosulfate, KHSO5
[CAS-RN 10058-23-8], commonly known as potassium monopersulfate, which is present as a component of a triple salt with the formula
2KHSO5·KHSO4·K2SO4 potassium hydrogen peroxymonosulfate sulfate.

The following are considered incompatible materials and should not be transported or stored in proximity to Oxone:
• Compounds containing halides or active halogens. Oxone® can oxidize halides to active halogens (for example, chloride to chlorine)
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,238
Tucson, AZ
We are aware of the interference and it was mentioned very early in this thread (posts 2 and 7). We also almost never recommend MPS.

We teach very specific methods. You are welcome to learn and use the TFPC method or not.
 

jseyfert3

Bronze Supporter
Oct 20, 2017
963
South-Central WI
Oh, I forgot to add: Both the link in post #2 and the instructions that came with my Taylor K2006 test kit state that MPS will not break down CCs. So you should not be adding it for that purpose.