BBB converter with a question

[BC]

Switched after finding this site. No complaints but have a question relating to getting the CC in line. Dichlor obviously is effective to stabilize when shocking but it adds to CYA which everyone here says is not good (once above 50). So I refilled 80% - 90% of a 365 gal capacity hot tub and started over - getting CYA controlled then switching to 6% unscented bleach. As part of the cycle CC rises so I shocked with bleach using the calculator as a limit. Attached is the spa log where I did this 3 consecutive days (end of DEC) with no real reduction in CC value. Then learned about MPS - so bought some and followed directions. Used weekly along with bleach since MPS is not a sanitizer (set the FC target during MPS shock at around eight). For a month, I still haven't been able to show a real significant CC drop (I believe target is <.5 or so).
Any suggestions?
Thanks,
Barry
[attachment=0:1qj2a2jt]spa log-1.xls[/attachment:1qj2a2jt]

 

[dschlic1]

You may have an organic load in your spa. Also MPS will show up as CC for a very long time after your use it. Try shocking your spa.

 

[BC]

Thanks,
Shock with bleach along with MPS?

 

[duraleigh]

I was unable to open the *.xls file which I assume contains your test results.

 

[chem geek]

If you are measuring the CC soon after your soak, then you will usually measure some and that is not a problem because it's just temporary -- chlorine combined with ammonia from your sweat/urine that will get broken down in about an hour. If you measure CC just before your next soak, then that would probably indicate your not using enough sanitizer/oxidizer, especially if the FC were near zero.

Every person-hour of soaking takes about 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach. A typical one person soak for 30 minutes or two people for 15 minutes would require about 2 teaspoons of Dichlor or 3 fluid ounces of 6% bleach. It may just be that you aren't using enough sanitizer to oxidize your bather waste.

Richard

 

[BC]

Thanks Richard,
Could you download the log where it records soaking activity along with daily additives?
It shows regardless of the usage - I can't get the CC down when FC is within acceptable range - shocking with bleach, shocking with MPS, and a combination of both....my FC consumption even without soaking seems to be 3 - 4 FC per day. It's not like we use this everyday - been sub-zero in Ohio for some time.
I guess i didn't think I would have to use the volume of bleach daily to keep the FC btw 3 -6 and not be able to shock it to affect the CC (other than using Dichlor).
Barry

 

[chem geek]

Barry,

I've looked at the log. Just so you know, MPS will usually register as CC on the test (if it's really high or very soon after adding it then it can even measure as FC). However, in your case, the CC is getting measured even without usage and before or after MPS would no longer be present.

By the way, 3 fluid ounces of 6% bleach in 365 gallons would be about 4 ppm FC. I'm not sure why your spreadsheet lists things like "4 oz bleach (8FC)" and "1.5 oz bleach (7FC)" and "3 oz bleach (8FC)". In the list below, I calculate the presumed chlorine demand or usage. Normally, the chlorine demand from a soak will occur soon after the soak -- 2/3rds of it during the soak itself and another 1/3rd in the hour or so afterwards. The following are some of the last entries in your spa log.

6.8 ppm FC
3.8 ppm FC
6.8 - 3.8 = 3 ppm FC chlorine demand with no activity -- this is very unusual
2 ounces bleach should raise the FC to 3+2.6=5.6 ppm
Soaked
0.8 ppm FC
5.6 - 0.8 = 3.8 ppm FC chlorine demand is to be expected after a typical soak, perhaps on the low side
5 ounces bleach should raise the FC to 0.8+6.6=7.4 ppm
5 ppm FC
7.4 - 5 = 2.4 ppm FC additional chlorine demand including the soak is reasonable. Including the above, this is 3.8+2.4=6.2 ppm FC
2+2=4 ounces bleach should raise the FC to 5+5.3=10.3 ppm
2.8 ppm FC
10.3 - 2.8 = 7.5 ppm FC chlorine demand after two soaks is reasonable, perhaps a little on the low side depending on soak time and number of people
2 ounces bleach should raise the FC to 2.8+2.6=5.4 ppm
4.8 ppm FC
4.8 - 2.8 = 2.0 ppm FC chlorine demand with no use is possible, though perhaps a little high
1.5+2=3.5 ounces bleach should raise the FC to 4.8+4.6=9.4 ppm
3.6 ppm FC
9.4-3.6=5.8 ppm FC chlorine demand is pretty high even for 2 days given that there was no soaking.

The CC shouldn't be persisting so is probably coming from something other than your sweat/urine. I also noticed you were adding enzymes and though that might help break down organics, they clearly haven't been helping to reduce CC and they just get broken down eventually with chlorine so increase chlorine demand. The KISS principle of keeping it simple applies here -- the less you add to the spa the better.

By any chance does your spa have an ozonator? If it did, then that could account for the chlorine demand when not soaking. However, your pH would probably be rising more if you had an ozonator. Is your spa covered when not in use? Is this a new spa or your first fill of water in it? Has the spa ever been super-chlorinated? When you say "soak", how many people and for how long? Is there anything else in the system like Nature2 or other ionizer?

Personally, unless you smell the CC, I wouldn't worry about it until the next time you do a refill. By the way, one of your measurements had "1.1" for CC. I presume you are using the FAS-DPD chlorine test with a 25 ml sample where each drop represents 0.2 ppm so is that an estimate in between drops or is it a typo?

What is interesting is that when you were shocking with bleach, the FC was dropping fairly rapidly, but you also had enzymes at that time and the shocking probably just got rid of the enzymes. Unless you believe you really need to use either MPS or enzymes, you could use neither and see if the chlorine demand stabilizes. Since even use of Dichlor got the CC up fairly rapidly while the bleach seems to have taken longer, I'm thinking that there is something in your water that combines more slowly with chlorine and stays persistent and my best guess would be the enzymes except that you saw this early on with Dichlor and didn't record any use of enzymes then.

Also, since this is water from a cistern, then the next time you refill the tub you should 1) use a water filter (softener) to remove calcium and iron, etc. and 2) shock with LOTS of chlorine -- 20-30 ppm FC and if you use Dichlor for this then that will get you the CYA you need pretty much in one shot. If you instead use a better water source, then you shouldn't need to go through this hassle.

Richard

 

[BC]

Barry,



By the way, 3 fluid ounces of 6% bleach in 365 gallons would be about 4 ppm FC. I'm not sure why your spreadsheet lists things like "4 oz bleach (8FC)" and "1.5 oz bleach (7FC)" and "3 oz bleach (8FC)". The (*FC) is just the target I was shooting for. In the list below, I calculate the presumed chlorine demand or usage.

The CC shouldn't be persisting so is probably coming from something other than your sweat/urine. I also noticed you were adding enzymes and though that might help break down organics, they clearly haven't been helping to reduce CC and they just get broken down eventually with chlorine so increase chlorine demand. That makes sense. The KISS principle of keeping it simple applies here -- the less you add to the spa the better.

By any chance does your spa have an ozonator? YES If it did, then that could account for the chlorine demand when not soaking. However, your pH would probably be rising more if you had an ozonator. Is your spa covered when not in use? YES Is this a new spa or your first fill of water in it? Less than a year old - 2 re-fills so far. Has the spa ever been super-chlorinated? NO When you say "soak", how many people and for how long? 2 people 45 mins avg. Is there anything else in the system like Nature2 or other ionizer? Have a Spa Frog cartridge in filter well.
Personally, unless you smell the CC, I wouldn't worry about it until the next time you do a refill. Really no smell at all even with CC values over 1.

What is interesting is that when you were shocking with bleach, the FC was dropping fairly rapidly, but you also had enzymes at that time and the shocking probably just got rid of the enzymes. Unless you believe you really need to use either MPS or enzymes, you could use neither and see if the chlorine demand stabilizes. Sounds like a plan - I'm all for less additives. Since even use of Dichlor got the CC up fairly rapidly while the bleach seems to have taken longer, I'm thinking that there is something in your water that combines more slowly with chlorine and stays persistent and my best guess would be the enzymes except that you saw this early on with Dichlor and didn't record any use of enzymes then.

Also, since this is water from a cistern, then the next time you refill the tub you should 1) use a water filter (softener) to remove calcium and iron, etc. and 2) shock with LOTS of chlorine -- 20-30 ppm FC and if you use Dichlor for this then that will get you the CYA you need pretty much in one shot. If you instead use a better water source, then you shouldn't need to go through this hassle. Thanks!

Richard

 

[chem geek]

Thanks for answering all of my questions. Since you have an ozonator, that's a mixed bag. I'm surprised that the ozonator isn't getting rid of the CC. In any event, using bleach with an ozonator can be a pain due to rising pH, but with the Borates you've added in your spa it looks like you're not adding too much acid that frequently. It's up to you, but if you had a way of disabling your ozonator (specifically, the entire unit including air injection), then that's another option to try. You certainly don't have to do this, but just keep in mind that with the ozonator you may have continued chlorine demand even when not using the tub.

More importantly, having 2 people soaking for 45 minutes at what I presume is hot temperature (100-104F) is 1.5 person-hours which would normally require about 10 ppm FC of chlorine in your sized tub to oxidize the bather waste. The ozonator might be helping here, though it might also explain the chlorine demand when you're not using the tub since the ozone can oxidize chlorine itself. The simplest approach would be to disable the ozonator and use more chlorine after each soak -- about 5 teaspoons of Dichlor or 7-1/2 fluid ounces of 6% bleach. I suspect that if you do this, you'll be able to retain a residual of chlorine much longer. So consider this for your next refill and at the start of your next refill be sure to super-chlorinate your spa. A new spa has all sorts of oils and other organics leftover so the first fill or two typically has a lot of chlorine demand.

If you intend to soak as long as you have been and if the water temp is high, then have the CYA level be on the higher side around 30-40 ppm rather than 20-30 ppm. That will help to moderate the higher FC level swings that you will be having right after your soak. The Borates will definitely be helpful as well to prevent the pH from rising too much when you add the bleach.

Richard

 

[BC]

Found this on the Taylor website explaining the effect using MPS has on the CC test. Thought it may partly or mostly explain the false high CC result I was getting.

http://www.taylortechnologies.com/Chemi ... ntentID=24

Especially since I really didn't notice unusually high chlorine smells or skin irratation with those readings.

I have since changed water (it was due) and now wondering if it's worth the purchase to get the reagent that they have to negate MPS oxidizing of the 0003 reagent? or just quit using MPS - though many people like it to help reduce FC being spent.
Barry