FC confusion after using MPS

[Bubbadubba]

Hi All,

I am new to hot tub ownership and I am still trying to get into a routine. I have a 450 gal saltwater tub and use the taylor test kit with FAS-DPD and the deox reagent for MPS.

I tested my water Saturday afternoon after heavy use the night before and my ph was 7.4, ta between 50-60,FC around 1.8 ppm and CC about 0.8. I then put in one tsp dichlor (to get the fc up a bit as the salt system is slow) and about 6 tbsp MPS oxidizer.

I tested my water yesterday early evening -- over 24 hours later -- and FC was 7 and CC was 1.4. I do have the Taylor Deox agent and tested using it, and then tested again without. I got the same results. I tested the water again this afternoon without deox and the FC was 2.2 and CC around 0.6.

Could someone help me understand why my chlorine numbers were so elevated? Could my deox reagent be faulty?

Thanks in advance,

Christian

 

[Methuselah]

Hi All,

I am new to hot tub ownership and I am still trying to get into a routine. I have a 450 gal saltwater tub and use the taylor test kit with FAS-DPD and the deox reagent for MPS.

I tested my water Saturday afternoon after heavy use the night before and my ph was 7.4, ta between 50-60,FC around 1.8 ppm and CC about 0.8. I then put in one tsp dichlor (to get the fc up a bit as the salt system is slow) and about 6 tbsp MPS oxidizer.

I tested my water yesterday early evening -- over 24 hours later -- and FC was 7 and CC was 1.4. I do have the Taylor Deox agent and tested using it, and then tested again without. I got the same results. I tested the water again this afternoon without deox and the FC was 2.2 and CC around 0.6.

Could someone help me understand why my chlorine numbers were so elevated? Could my deox reagent be faulty?

Thanks in advance,

Christian

Since you are using dichlor you do have an unknown to contend with, namely the CYA (stabilizer) level. You need to know that and adjust FC target level appropriately.

Saturday, FC 1.8, CC .8 (adding dichlor and MPS).

That will kick up FC quite a bit (which it did), which, in conjunction with MPS, should help to knock down CC.

Sunday, FC 7, CC 1.4 (same results with or without Deox).

FC up, but didn't knock out CC. Perhaps your CYA is high and the FC not as effective as you need?

Monday FC 2.2 and CC .6.

Getting there, maybe with help from SWG?

I suppose your CC of 1.4 could have been interpreted higher than it actually was ... the Deox reagent instructions boggle my mind because you add drops until the last has no effect. So what if it has minimal effect one time and lots the next ... seems readings are approximate to me, and the change subjective.

Anyway, the CYA reading can be bounced against this chart.

As to MPS that's kind of controversial and there isn't a ton of info or guidelines on using it. It adds sulfates to the water (algae food), and some believe it better to keep things simple claiming you don't need it, or need to add anything to the tub that isn't essential.

 

[Bubbadubba]

Since you are using dichlor you do have an unknown to contend with, namely the CYA (stabilizer) level. You need to know that and adjust FC target level appropriately.

Saturday, FC 1.8, CC .8 (adding dichlor and MPS).

That will kick up FC quite a bit (which it did), which, in conjunction with MPS, should help to knock down CC.

Sunday, FC 7, CC 1.4 (same results with or without Deox).

FC up, but didn't knock out CC. Perhaps your CYA is high and the FC not as effective as you need?

Monday FC 2.2 and CC .6.

Getting there, maybe with help from SWG?

I suppose your CC of 1.4 could have been interpreted higher than it actually was ... the Deox reagent instructions boggle my mind because you add drops until the last has no effect. So what if it has minimal effect one time and lots the next ... seems readings are approximate to me, and the change subjective.

Anyway, the CYA reading can be bounced against this chart.

As to MPS that's kind of controversial and there isn't a ton of info or guidelines on using it. It adds sulfates to the water (algae food), and some believe it better to keep things simple claiming you don't need it, or need to add anything to the tub that isn't essential.

Thanks for the response.

I actually don't use dichlor that much and mostly rely on the salt water chlorine generator. I checked the CYA 2 weeks ago and it was less than 20 ppm. Since then I have put less than 2 Tbsp of dichlor in. My CYA is probably between 20-25 now.

Using the pool calculator, my FC numbers make sense to me after usage and adding the Dichlor. What doesn't make sense to me are the FC and CC numbers within 48 hours of MPS application. The whole purpose of me buying the Deox reagent was to be able to test accurately when MPS is in the water.

I do agree that the instructions for the deox are odd. Maybe I am doing the test wrong? Who knows...I guess I will just assume if I want accurate chlorine numbers I need to wait until there is no MPS in the water.

 

[JoyfulNoise]

You should not add MPS and dichlor at the same time. Doing so only defeats the intended purpose of the MPS which is to oxidize organic waste BEFORE chlorine can react with it. When you spike both the chlorine levels and add an additional oxidizer, the two can work against each other.

Next time add the MPS first and let it work for 24 hours before adding more chlorine. You can use the MPS deoxidizer reagents to get a rough idea of chlorine concentration separate from MPS to see if you’re hitting your dosing target.

Remove the SWG when adding MPS. The high sulfate levels lead to faster deterioration of the catalytic coating on the SWG plates.

 

[Bubbadubba]

You should not add MPS and dichlor at the same time. Doing so only defeats the intended purpose of the MPS which is to oxidize organic waste BEFORE chlorine can react with it. When you spike both the chlorine levels and add an additional oxidizer, the two can work against each other.

Next time add the MPS first and let it work for 24 hours before adding more chlorine. You can use the MPS deoxidizer reagents to get a rough idea of chlorine concentration separate from MPS to see if you’re hitting your dosing target.

Remove the SWG when adding MPS. The high sulfate levels lead to faster deterioration of the catalytic coating on the SWG plates.

Thanks, appreciate the good info.

Regarding shutting off the SWG to extend lifetime, is that for a full 24 hours? I am usually adding the MPS after a night of heavy use, and the chlorine levels are pretty low at that point. This is why I added the dichlor at the same time. Should I be worried about sanitation while adding MPS if the chlorine levels are at 1 ppm?

 

[Methuselah]

You should not add MPS and dichlor at the same time. Doing so only defeats the intended purpose of the MPS which is to oxidize organic waste BEFORE chlorine can react with it. When you spike both the chlorine levels and add an additional oxidizer, the two can work against each other.

Next time add the MPS first and let it work for 24 hours before adding more chlorine. You can use the MPS deoxidizer reagents to get a rough idea of chlorine concentration separate from MPS to see if you’re hitting your dosing target.

Remove the SWG when adding MPS. The high sulfate levels lead to faster deterioration of the catalytic coating on the SWG plates.

Pure gold, Thanks!!!

 

[JoyfulNoise]

Thanks, appreciate the good info.

Regarding shutting off the SWG to extend lifetime, is that for a full 24 hours? I am usually adding the MPS after a night of heavy use, and the chlorine levels are pretty low at that point. This is why I added the dichlor at the same time. Should I be worried about sanitation while adding MPS if the chlorine levels are at 1 ppm?

You use MPS to help oxidize bather waste when you see that the CCs are starting to remain persistent. It’s not something that should be needed regularly. Honestly speaking, if a hot tub is properly sanitized and maintained with chlorine, you shouldn’t need any MPS at all. At the very most, I wouldn’t add it more than once per week. It should be added when the chlorine is low, say after a soak, and then given several hours to work before trying to bring the chlorine levels back up. If you have a heavy use evening, then you should add it after the soak and let it work overnight (with the usual filter/recirculation schedule running). Then you can bring the chlorine levels back up in the morning.

I don’t know if you already posted this, but if you haven’t used Ahhsome to purge your hot tub, you should consider doing a purge and fresh fill. Persistent CC levels and difficulty in maintaining FC are hallmark signs of contaminated plumbing. Ahhsome will help to lift and purge any biofilms in the plumbing.

 

[Bubbadubba]

You use MPS to help oxidize bather waste when you see that the CCs are starting to remain persistent. It’s not something that should be needed regularly. Honestly speaking, if a hot tub is properly sanitized and maintained with chlorine, you shouldn’t need any MPS at all. At the very most, I wouldn’t add it more than once per week. It should be added when the chlorine is low, say after a soak, and then given several hours to work before trying to bring the chlorine levels back up. If you have a heavy use evening, then you should add it after the soak and let it work overnight (with the usual filter/recirculation schedule running). Then you can bring the chlorine levels back up in the morning.

I don’t know if you already posted this, but if you haven’t used Ahhsome to purge your hot tub, you should consider doing a purge and fresh fill. Persistent CC levels and difficulty in maintaining FC are hallmark signs of contaminated plumbing. Ahhsome will help to lift and purge any biofilms in the plumbing.

So much good info, thank you guys!

I will add ahhsome to my list of chems. FYI, the hot tub is brand new and was installed and filled on 11/7, so I would hope my plumbing isn't contaminated lol. I have a pool, so I wasn't starting from scratch regarding water care. CC is on average is 0.4 to 0.6. Higher than my pool, but not too bad I think.

Christian

 

[JoyfulNoise]

So much good info, thank you guys!

I will add ahhsome to my list of chems. FYI, the hot tub is brand new and was installed and filled on 11/7, so I would hope my plumbing isn't contaminated lol. I have a pool, so I wasn't starting from scratch regarding water care. CC is on average is 0.4 to 0.6. Higher than my pool, but not too bad I think.

Christian

You would think a new hot tub is clean but you would be wrong. They are pressure tested and system tested at the factor. Then they drain the water out of the tub. But plenty gets left behind in the plumbing. They then wrap the tub up in plastic and ship it off to the hot tub store where it sits in their warehouse for months before it’s sold. All the while the stagnant water sits in the plastic piping growing mold, bacteria and biofilms. “But there’s no light or food sources!” you say … “How can anything grow?!?” Plenty of organic (vegetable) grade greases used on the plumbing fittings to provide an ample source of food and neither bacteria nor fungi need much of any light.

Believe me and others here who have witnessed first hand the gunk that comes out of a “new” tub … your plumbing is not clean …

 

[Bubbadubba]

You would think a new hot tub is clean but you would be wrong. They are pressure tested and system tested at the factor. Then they drain the water out of the tub. But plenty gets left behind in the plumbing. They then wrap the tub up in plastic and ship it off to the hot tub store where it sits in their warehouse for months before it’s sold. All the while the stagnant water sits in the plastic piping growing mold, bacteria and biofilms. “But there’s no light or food sources!” you say … “How can anything grow?!?” Plenty of organic (vegetable) grade greases used on the plumbing fittings to provide an ample source of food and neither bacteria nor fungi need much of any light.

Believe me and others here who have witnessed first hand the gunk that comes out of a “new” tub … your plumbing is not clean …

Well shoot, good to know. I never would have thought about that.

Unfortunately the logistics and trying to purge, drain, and refill the hot tub right now would be be difficult, as I am in the northeast and we have sustained cold temperatures. My sanitizer levels don't drop suddenly, the water is crystal clear, and my ph is stable. Is this something I should worry about?

 

[Newdude]

Is this something I should worry about?

You're no worse off than you were yesterday.

Plan on purging at your earliest convenience. These days the weather is drunk. It might be 75 in a couple weeks. (or at least more tolerable to play with water)

 

[JoyfulNoise]

Typically it is recommended that you don’t go more than 2 to 3 months between hot tub water exchanges. I know that people try to stretch it out for as long as possible because of the labor involved in draining and cleaning a tub. So all that can be said is you should do the purge at you next available convenience and try not to push it too far. If you have to bite the bullet and spend a long cold afternoon battling with submersible pumps and hoses, well, yeah … that’s life with a hot tub.

 

[JoeSelf]

Get Ahhsome for the purge, and AquaClarity to use weekly. Keeps the pipes clean and helps with ph rise once you get it stable.