Chemistry Issue

[socal147]

Constantly fighting pH.
I always find my pH drifting high.
I corrected an earler error reporting TC vs FC. Sorry for the confusion.

Day 1
Alk 150
CH 200 (This remains constant)
FC @1.5 - 3
pH @ 8
Add pH down to ph 7.5

Day 2
Alk 130
FC zero (0) adj to 1.5 - 3.0
Ph 8
Add pH down to pH 7.5

Day 3
Alk 110
FC zero (0) adj to 1.5 - 3.0
Ph 8
Add pH down to pH 7.5

Day 4
Alk 90
FC zero (0) adj to 1.5 - 3.0
Ph 8
Add pH down to pH 7.5

Day 4
Alk 70 - Adj to 150
FC zero (0) adj to 1.5 - 3.0
Ph 8
Add pH down to pH 7.5

Go back to DAY 1 and repeat.

Is this normal?

[fdegree]

I am not an expert on this stuff, and I still have a lot to learn.  But, I have found if I keep my Total Alkalinity (TA) down around 50, my pH doesn't rise quite so bad.  A TA of 50 may not be right for you.  If lowering your TA works, you'll have to play with it to determine what level is best for your situation.

Here something that was written by someone else that may help:
_______________

pH will have a tenancy to rise with aeration (i.e. use of jets and air), more so if your TA is high. Although, as long as you're not adding Acid (or anything with a lower pH) to your tub, the pH will not usually drop. Therefore, in hot tubs the problem is normally pH rise (or Drift), because of all the aeration. So the trick is to get the TA high enough to not create an unstable situation, and low enough to not allow pH to rise too much.

Let me repeat the last sentence, because it's the single most important thing to keeping your water balanced. The key to having balanced water, without pH drift, is having the correct TA level. If you find your pH rises too high (>8.0) after using your tub, your TA is too high, and needs to be lowered. If you find your pH is too low and/or your water is continually acidic, your TA is too low and needs to be raised. By fine tuning your TA, you can get your pH perfectly balanced, that rarely needs adjustment.

[socal147]

I thought we were shooting for a TA of 125-150 (BullFrog chemistry ref.) . What your saying makes sense though.

[chem geek]

Pools and spas are intentionally OVER-CARBONATED.  Having Total Alkalinity (TA) as well as Calcium Hardness (CH) in plaster pools saturates the water with calcium carbonate in order to protect plaster surfaces.  The higher TA is not only a pH buffer, but it is also a SOURCE of rising pH in its own right.  This is because the amount of carbon dioxide in pool/spa water is higher than the equilibrium amount with the carbon dioxide in air.  So this excess carbon dioxide outgasses, especially when there is hotter water and more aeration, and that makes the pH rise because removing carbon dioxide from the water is essentially removing carbonic acid.

This post shows how much higher the carbon dioxide level is in water compared to its equilibrium amount with air at various pH and TA levels.  Ignore the color coding -- in spas the higher temperature and aeration means that even much of the green area leads to rising pH.

A higher TA level is needed when one is using net acidic sources of chlorine or bromine or oxidizers.  So usually using Dichlor or MPS requires a somewhat higher TA, though not usually more than 80 ppm.  Use of a hypochlorite source of chlorine such as bleach, chlorinating liquid, Cal-Hypo (not usually a good idea due to it increasing CH) or lithium hypochlorite is close to pH neutral because the consumption/usage of chlorine is acidic, but this requires the TA to be very low such as 50 ppm.  Many people find that it is very helpful to not only keep the TA low, but to use 50 ppm Borates such as from ProTeam® Gentle Spa since this provides additional pH buffering without the side effect of pH rise (since the borates do not outgas).  What are you using for chlorine?  What is your regimen?

The other problem I noticed is that you are letting the chlorine level get to zero.  If it is zero for too long, then pathogens such as bacteria can grow and also form biofilms.  Generally, you want to add sanitizer/oxidizer right after your soak and add enough so that you end up with 1-2 ppm Free Chlorine (FC) at the start of your next soak.  A rough rule-of-thumb without an ozonator is that every person-hour of soaking in a hot (104ºF) tub requires 5 fluid ounces of 6% bleach or 3-1/2 teaspoons of Dichlor or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize bather waste and still have a residual sanitizer amount.  With an ozonator, these amounts are usually cut roughly in half if the spa is used daily, though for spas only used 1-2 times a week or less an ozonator roughly doubles daily chlorine usage (ozone reacts with chlorine to form chloride and chlorate).

Since you are only reading a Total Chlorine (TC) reading, it sounds like you aren't using a proper test kit.  If you are using test strips, they are often inaccurate compared to drop-based tests.

[socal147]

I am using a Taylor 2006K.
After each evening use I add a 1/2 teaspoon(ish) of Dichlor to reach the 1-3 FC (Incorrecty posted as TC). Usually it ends up @ 3ppm.
The next morning my FC is Zero.
I add the 1/2 teaspoon(ish) Dichlor and the FC reading goes back to @3ppm,  ph is @8, and TA falls post pH down addition.

I will let the TA come down to @80. Adjust ph to @7.6, and double up my Dichlor addition.

I use the spa every evening. I shocked with Dichlor today. No cloudiness or growth has been observed to date.
I will update with results.....
Thanks.............Patrick

[fdegree]

Glad to see chem geek step in...much of what I have learned has come from him.  He is very knowledgeable about this stuff.  He should be able to get you on track

[socal147]

My BullFrog 231 is only around 250 gallons with three week old water. I am the solo user on a daily basis.

0815: I shock with Dichlor to 20 ppm.

1408:
FC - 1.8  CC 0.6. Added a teaspoon of MPS. FC indicates 2.8 (Erronous?) and CC dropped to 0.2.
pH is 7.5. Adjusted from @8 with pH down.
TA is 100

The overcarbonated part makes perfect sense. My spa was very "soda pop" like, fizzing away while I soaked. I work in the power/water industry so the chemistry is not a mystery. I guess following the 'standard' guidelines messed me up. But....it makes sense.

I will be checking my chemistry in another hour or so. I am curious to see what if anything changes. 

Thanks for all of the support and a special thanks to Chem Geek.

[chem geek]

1/2 teaspoon of Dichlor with no ozonator or any other oxidizer added is only going to handle the bather waste of one person soaking for a little under 10 minutes in a hot (104ºF) spa.  So unless your soaks are very short or your water is a lot cooler than a typical spa, you are using WAY too little chlorine.  In fact, your spa may now be way behind with loads of urea left to oxidize so you may find your chlorine demand to be high even when you increase how much you add, at least until you catch up.

If you use only Dichlor for your sanitation/oxidation, then the Cyanuric Acid (CYA) level will build up over time.  For every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases CYA by 9 ppm.  With your small tub, this will build up fairly quickly requiring you to change the water sooner.  If you were to use Dichlor-then-bleach, you could probably go twice as long between water changes, but why don't you first get your Dichlor-only regimen in shape first.

[socal147]

Ozonator - by this do you mean the Spa Frog. I am currently using one but was unsure of the benefit. I did shock today and the chemistry seems to be maintaining. I will check CYA.

Thanks,
Patrick

[socal147]

CYA test was 0. I ran it twice to confirm results. There was absolutely no cloudiness in either test sample. My test kit is new so I trust the reagents.

SBS - Sodium BiSulfate - ph Down - We use this chemical at our treatment facility to eliminate chlorine. I understand how it lowers pH but wont I also lose on the FC side?
Na(CO3)2 - Sodium BiCarb - For Alkalinity - SBS has little effect(?) but Vinegar would react quite quickly and lower the pH. Good or bad thought?

Thanks in advance

[chem geek]

1/2 teaspoon of Dichlor in 250 gallons would be only 1.4 ppm FC so after 3 weeks (21 days) that would be around 26 ppm CYA.  Though that would normally make the CYA test at least somewhat cloudy, since you aren't using enough chlorine and it gets to zero it's possible for bacteria to have converted the CYA into ammonia.  I had that happen in my pool once when I let it go by accident.  If you are testing it with the water hot rather than room temperature, that might also affect the test (i.e. melamine cyanurate may be more soluble at higher temperature).

Sodium bisulfate (NaHSO₄) does NOT eliminate chlorine; it is a dry acid that lowers pH.  I believe you are confusing that with sodium bisulfite (NaHSO₃) which is a reducing agent that will get rid of chlorine, similar to sodium thiosulfate (Na₂S₂O₃).

Vinegar at usual concentrations with acetic acid at < 10% is a far weaker acid in concentration than sodium bisulfate.  It also adds organics to the water, specifically acetic acid which can react with chlorine to form haloacetic acids (HAA5) which are disinfection by-products with possible health impacts.  If you really want a stronger (more concentrated) acid, then there's Muriatic Acid (31.45% Hydrochloric Acid), but if you go that route I suggest getting the half-strength (15-16%) since that fumes a lot less.

If you used the proper amount of Dichlor after a soak, I think you'd find that your pH wouldn't rise so much because Dichlor is net acidic when accounting for chlorine usage/consumption (technical details about this are in this post).  If you were to use the Dichlor-then-bleach method, then you would not only have your TA be very low (around 50 ppm), but would also use 50 ppm Borates (boric acid) as an additional pH buffer.  The borates are found in products such as ProTeam® Gentle Spa.  If you do want to just skip to the Dichlor-then-bleach method, then a full write-up for it's use is in this post (summary at the end of the post).

As for TA, any acid will lower both pH and TA so I don't understand what you mean when you say that sodium bisulfate has little effect.

As for an ozonator, I mean a device (corona discharge aka CD or ultraviolet aka UV) that produces ozone.  The Spa Frog is a mineral ion system that comes in cartridges that release copper and silver ions into the water.  They do nothing to oxidize bather waste.  They mostly just inhibit uncontrolled bacterial growth.  A comparison of chlorine kill times vs. copper and silver is in this post.  Since chlorine kills most pathogens much more quickly than copper or silver, the metal ions are at best just an insurance policy in case you don't maintain proper chlorine levels.

[socal147]

^^^ Very good ^^^ Post soak last night, I added 2 teaspoons of Dichlor. The chemistry prior was (presoak) perfect with FC at 1.8. The pH has maintained a lower value of 7.8 - I did adjust to 7.6. The fizziness I experienced during prior usage is almost gone. I will keep up the Dichlor routine and monitor the results.

Sodium bisulfate and ite. Simple errors can kill a good intention.

0425 - Doing chemistry before it is light out is a different experience.
FC - 2.8
pH - 7.8
Added a teaspoon of DiChlor and 1/2 Teaspoon of pH down. I work today so I want to ensure my FC stays up. I am happy to see the FC stay positive overnight. That is a first.

I will update this evening and again thanks for the education.
Patrick

[socal147]

1820:
FC - 1.2
TA - 100
pH 7.8

FC - added 1 teaspoon Dichlor
Ph - Added ph Down to 7.6

FC - I had some left over from this morning.  TA is slowly coming down.  pH adjust was much quicker.

Win Win Win situation. 

[chem geek]

Good.  You are getting a handle of the situation and are moving to the next level.  You'll then be like a Dichlor-only spa user properly maintaining their spa.  At that point, you'll find that the water will only last so long.  Roughly speaking, you'll get the standard Water Replacement Interval (WRI) time which is (1/3) x (Spa Size in U.S. Gallons) / (# of Bathers) where the assumed soak time is around 20 minutes or so.  For a 250 gallon spa with one person soaking every day for 20 minutes, that's (1/3) x (250) / (1) = 83 days or not quite 3 months.  If you soak longer, such as 30 minutes, then that's more like 56 days (not quite 2 months).  One can always go longer, but the water quality will be noticeably degraded (duller) since the rising CYA level will slow down oxidation and disinfection rates (yes, this increases the risk of getting hot tub itch/rash/lung).

If you were to use Dichlor for about a week to get the CYA to 30 ppm and then switch to bleach (except for one day a month with Dichlor to replenish lost CYA), you could go around twice as long between water changes and have the water remain at better quality as well, but you'd need to get your TA low to around 50 ppm and should use 50 ppm Borates for more pH control (and some other benefits).  So try things out for a while with Dichlor-only -- perhaps for this entire time before the next water change -- and if you want to try Dichlor-then-bleach, then check back in with us or read the link I gave earlier and go from there.

[socal147]

Thanks Chem Geek. Since this is my first batch, I will likely be dumping sooner than later. I am a solo user but expect guest throughout the summer. The DiChlor/ Bleach method sounds interesting and I will probably try it in the future. I will review the link prior to jumping in.

Thanks again,
Patrick