Ph still high after muriatic acid additions

[Nakubda]

Having recently superchlorinated my hot tub following likely severe bacterial contamination am strongly focused on getting/keeping hot tub in good balance.
After several day decontamination procedures, filled last Sunday 3-22.
Original #s were: FC 0-1
Ph 7.9 or higher (my tap measures over 8.2)
TA 180-190
CH 100
CYA <30

In increments have added 23 t muriatic acid (3-5 t at a time)
6.4 oz chlorine, then dichlor to increase CYA, so far approx 2.5 T

Current #s are: TC 4.5, FC 4.5, CC 0
Ph 7.7
TA 100
CH 230 (Sundance tells me to shoot for 200-400, tried to shoot low in range)
CYA <30
I know I need to get the CYA up, which is why I switched to adding DiChlor until it's up, then I'll switch back to bleach.

My questions are:
1) Should I keep adding muriatic acid to decrease Ph even though numbers are in a good range, or should I wait and see how it behaves?
2) Should I give it a super shock when first starting up? That would be a way to get CYA up quickly but is there any other reason to do a strong shock upon start-up?
3) Any tips for measuring Ph more accurately. Can't think of any variations since I can't dilute with such a small range. One pool store measured the same as me in past few days (7.7) while another measured 8.2 when I estimated 7.8. The color almost looks in a different scheme than the color legend, appearing 'brighter' or 'whiter' but not as dark as the upper level, 8.2.
4) In general, what does it mean to 'maintain' chlorine level (since it's always dissipating). Is the monitor of <1ppm decrease FC in 8 hours or overnight the measure of this?
5) From your site I understand muriatic acid decreases TA and aeration increases Ph, but I just wanted to check that that is correct as some early threads state 'the only way to decrease TA is with aeration'.
6) Any particular tips for handling M.A.? I'm pouring in a glass measuring cup, then easily measuring into a teaspoon measure over the tub while running. I'm careful not to touch, breath or have near other chems, esp chlorine. Everyone seems scared of it, just wondering if there's something I'm missing.

Finally, let me say thank you for the great information you've already given me before this first post. I've been plagued with a complex, expensive and difficult situation for many months and your site has been a salvation. That includes the TF-100 test kit which empowers me to know my own numbers. Can't thank you enough already.....

 

[duraleigh]

Welcome to the forum!

You have done a lot of homework.....it's great to see a first-time poster that has already absorbed so much.

I'm not a hot tub guy but I can help with a couple of things.......

1. Not completely confident about tubs...pools I would suggest going on down to 7.4 but others will be along soon to add better advice.

2. No need, really. You have 0 cc's (which is a key indicator to determine whether to shock) and I'm quite sure your water looks good. I wouldn't shock.

3. Interpreting pH has a learning curve. It's not a bad idea to get a second opinion several times. You'll soon find you are agreeing more and more as you reinforce one anothers interpretation. I felt very uneasy about it at first and it is second nature now.

4. Good question. It means dosing your water in a manner that never allows your chlorine to fall below a certain level. So let's say 3ppm is your lowest acceptable level (depends on your CYA level). You discover thru experience that you lose an average of 2ppm daily in your hot tub. You would "maintain" your FC level of 3ppm by adding 2ppm daily....bringing the FC to 5ppm when you add and then allowing it to drop to 3ppm before you add to get it back to 5ppm.

5. That's a semantics issue.....more to come later :lol:

6. Muriatic can give you a nasty bite....fume-wise, clothes-wise, or skin-wise. (BTW, is that a metal teaspoon....uh-oh? ) I'm pretty comfortable dealing with it around a pool because I am always ready to immerse any spill I get on clothing or skin in the pool. Common sense and careful, deliberate handling will keep you safe. You'll get the fumes sooner or later and you will remember to keep it downwind from that point.....it's a real attention getter.

 

[chem geek]

(I wrote this as duraleigh/Dave was posting so some duplicate info here)

In a hot tub, you usually want the Calcium Hardness (CH) not higher than around 150 ppm. The higher water temperature is more likely to scale and hot tubs tend to go high in pH, especially if you use bleach instead of Dichlor. You would keep the TA lower and not above 80 ppm.

1) I wouldn't bother lowering the pH when it's at 7.7 just yet. See where it goes and how quickly. I suspect it will rise with aeration from the jets because your TA is on the high side so if it looks like it's headed towards 8.0 you can add some acid to lower it.

2) You could do a shock with Dichlor which will get your CYA up, but it's not necessary to shock unless it's a new tub or you are decontaminating (after letting the tub go for some time). Since you just superchlorinated your tub, you could just start off using Dichlor for around a week or so until you've cumulatively added around 30 ppm FC or so and then switch to using bleach.

3) Trust your own pH test kit unless you think you are color blind. You are probably right and the pool/spa store is probably wrong. You want to match based on hue (as much as possible), not saturation.

4) In a spa, you'll lose chlorine a lot faster due to the higher temperature and increased aeration as well as the much higher bather load. The chlorine demand is likely to be 25% per day, not a little drop of < 1 ppm FC overnight (and the overnight doesn't matter since keeping the tub covered during the day should have a similar loss.

5) Acid lowers both pH and TA. Aeration increases only pH with no change in TA. The statement you refer to should have said "the only way to decrease TA (alone) is with a combination of acid addition and aeration".

6) You seem to be handling the acid well. Though you should have the circulation pump running, do not run the jets when you add any chemicals to the spa or else it could splash back into your eyes. Wearing glasses or goggles is extra safe.

I presume you've already read this post. There's also one on chlorine demand (on another forum) here.

Richard

 

[PaulR]

For a hot tub, dry acid is easier to handle. I wouldn't want to mess with teaspoon quantities of muriatic.

Wet or dry, you might want to dip a bucket of spa water, put the acid in the bucket, stir/dissolve (not with your hand ), and pour the bucket slowly back into the tub. Then you're not relying solely on the tub circulation to dilute the acid.

--paulr

 

[Nakubda]

Thanks for all three helpful responses. (I just wrote this and saved to take time to re-read the links Richard included, but find no drafts...not sure what happened)

I'm confused about ideal chemical balances for my particular situation. I've updated my profile to include more info: I have an ozonator, a circ pump running 24 hrs/day. Also, the temp is around 100 and I was using a Nature II (silver) cartridge, tho haven't put in next one til chems balanced.
(7) Any thoughts about what's correct for my situation? If not certain, I'm going with your recommendations from now on.

Hottub manual: Sundance w.adjust for Nature II: Richard: nitro:
PH - 7.4-7.6 7.2-7.6 7.4-7.6
T.A.- 100-120 80-120 <=80 50-80
C.H.- 150-250 200-400 <=150 100-150

The review of the nitro post (Thanks Richard) was helpful to re-read, again. Had not known to check the CH first. I'm disappointed (but glad to know) to see info about CH as I deliberately increased it two days ago, thinking I had to get it btw 200-400 - at least glad I shot for the low end. (8) Is this high enough that I need to address with a water replacement? (currently 230)

Follow up questions:
(2) & (4) I was actually asking about how to judge chlorine level is being 'maintained' in a shock (for contaminants) situation, though much appreciate the new info about routine maintenance as well. After review of other threads I do feel more clear. I know the '<1 ppm drop overnight' was related to suggestions (Richard I think) for someone w contamination, and had to do with not lowering the FC level to bathing levels until the higher shock FC level was maintained. And i understood that one should look for 1) <1ppm drop FC overnight, 2) <=.5 CC level and 3) clean water, to determine that you are done shocking and can go to bathing levels.
(My water was clear and smelled fine even when contaminated w. several strains of staph, pseudomonas, and other stuff. It also survived several decontam. efforts so this info was very helpful, though I hope to prevent it ever happening again)
Regarding 'routine' maintenance, I'm assuming I shouldn't determine my normal FC drop rate until CYA is up. My intent when CYA is up to 20-30 (and PH and TA in balance) is to monitor typical FC drop level both without bathers and with bathers. Then follow general nitro and TFP rules.

(1) & (3) & (6)
I understand I should keep using M.A. to decrease Ph. I'll adjust as needed, and now assume w slightly lower TA than I have now (100) it should stay more stable.
I have gotten enough of a whiff of MA to respect it.
My spoon is hard plastic, rinsed immediately after using.
PH test reading - appreciate the validation that it takes some time to 'get it'. As I get used to TF-100 am using strips and my old BioGuard drop kit in the transition. I find the colors off there too (good thought, but I know for sure I'm not color blind), and am now wondering if it's because it tends to run high enough that I rarely see it in the good zone.

(5) Richard - thanks, that's exactly what I thought.

Thanks again for all your help.

 

[PaulR]

(7) & (8) As you can tell there is a lack of firm consensus on the appropriate target values for spas. I would use JasonLion's Pool Calculator to plug in your numbers and see what it comes up with for your CSI; if it's outside the comfort zone (-0.6 to +0.6) then you need to do some what-if experimentation with the calculator to see how much to fiddle the TA and CH.

As a rule, TA and CH should be lower for spas than for pools, I think mainly because of the higher temperature in a spa; the temp has a big effect on CSI.
--paulr

 

[chem geek]

Having an ozonator complicates things because sometimes it helps lower chlorine demand by handling some of the bather load while at other times it has you use more chlorine as the ozone can oxidize the chlorine (to chlorate). Which way this goes depends on the strength of your ozonator and the bather load. You've already got Nature2 as an insurance policy in case the chlorine level gets too low; an ozonator isn't particularly useful in a chlorine spa. It's more useful when using bromine, but that is not compatible with Nature2; it might be useful using non-chlorine shock (MPS) with Nature2. I'm not suggesting you change anything; just pointing out that the ozonator complicates things.

As Paul points out, the high temperature of the spa tends to cause scaling more readily so normally you have a lower Calcium Hardness (CH). Spas also often have a lot of aeration so the pH can rise which also increases the risk of scaling.

The hot tub manual and Sundance recommendations probably assume you will be using Dichlor-only or possibly MPS. Either way, these are net acidic when accounting for chlorine usage so is why they recommend a higher TA level. The recommendation from Nitro and myself is when you are using bleach since you want to minimize the rate of pH rise and that is done by having a lower TA level. You can also use 50 ppm Borates as an additional pH buffer, but I'd get the other water chemistry parameters into place first, including getting the pH more stable with a lower TA before you try the Borates.

As for your current CH of 230 ppm, it's not a disaster and it'll be OK if you get your TA down lower to no more than 80 ppm assuming that lets you have your pH be around 7.5 or 7.6 and not creep up above 7.7. With an ozonator, you may find that the pH tends to rise unless you get your TA down to 60 ppm or so (the ozonator is aerating the water).

The rule for the "< 1 ppm FC" loss overnight, "<= 0.5 ppm CC" is for pools. As I mentioned before, you may find that you lose around 25% of your FC in a hot tub with no bather load in one day so the overnight loss could be more than 1 ppm FC depending on your FC level (i.e. if it's > 4 ppm FC) if you keep the water hot. This is normal and not indicative of a problem.

How did you know that the spa was contaminated with several different strains of bacteria?

As for determining the normal chlorine demand (drop), yes you should wait until your CYA is up as that will help somewhat to lower the rate of that loss through less chlorine outgassing.

As for acid, use whatever you feel comfortable with. Dry acid is certainly easier to handle, especially in smaller quantities, and the suggestion for pre-mixing into a bucket first works well in general for either form of acid.

At some point, you'll need to decide how much chlorine you are willing to soak in. Most people add chlorine after their soak in an amount enough to measure a small (around 1 ppm FC) residual by the next time they soak. This is fine for preventing bacterial growth and for getting rid of bather waste after the soak, but it isn't enough to prevent person-to-person transmission during the soak. To do that, you'd have to have enough chlorine at the start of our soak to handle the bather waste -- usually around 4 ppm FC or so but this depends on the size of your tub, the number of people soaking, and the length of soak time. The downside is that you'll likely smell the chlorine during the soak.

A rough rule of thumb that works well in hot (104F) tubs is that every person-hour of soaking requires 3-1/2 teaspoons of Dichlor or 5 fluid ounces of bleach or 7 teaspoons of MPS in order to oxidize the bather waste (mostly urea and ammonia from sweat and urine). However, you'll need to experiment to determine actual usage in your situation, especially since you have an ozonator. The rule of thumb is without an ozonator. A CD ozonator is better than a UV one and may cut down your oxidizer demand in half during moderate-to-heavy bather loads, but may increase your chlorine demand when the tub is not in use -- possibly to 50% loss per day. Again, you'll just have to experiment/measure and see how things go. If there were a simple way to disconnect the ozonator (both ozone generation and air injection), that would be interesting to try at some point (but don't do anything that would void the warranty!).

Richard

 

[Nakubda]

Thanks again for your thoughtful reply, Paul. I've been using the calculator but hadn't focused on CSI...will do.

Richard.....WOW. I'll get back to you with some detailed responses but in the meantime, thanks so much for your pointedly accurate and focused responses...very impressive and helpful. More later...Melinda