Lowering PH - Use PH Down, Muriatic Acid or Vinegar?

[Quickbeam]

Please forgive my questions on this, but this is my first hot tub and I’m trying to get a handle on the water chemistry. Haven’t filled the tub yet but hope to do so this weekend. I should also point out that my wife has some pretty serious chemical sensitivities and given this we are going to try using hydrogen peroxide as a sanitizer. So here goes.

In another posting I posted that the results of my tap water are as follows:

PH - 7.4
TA - 220
CH - 210

I have done a fair bit of reading, and given that my TA is so high, I’m assuming that as soon as I turn on the jets on the tub my PH is going to go quite high as well. Assuming that this will in fact happen, would I be better off using PH Down, Muriatic Acid or Vinegar? I would ask that you please keep in mind that, as previously mentioned, my wife has chemical sensitivities and we are using hydrogen peroxide as a sanitizer.

I’d be curious to here from anyone on this, but am especially interested to hear from Chem Geek. I’m pretty sure my wifes’ preference would be to use vinegar, but from the reading I’ve done it seems that from those “in the know” vinegar is not the best option, but then I don’t know if they are factoring in the issue of the chemical sensitivities. I am also assuming that if we were to use vinegar we would need to use a truckload of it, and am not sure if this would create an unwanted vinegar odor, or would that odor just dissipate? I also thought I remembered reading somewhere that vinegar does not react well with hydrogen peroxide??? Having said all this, if I end up using either PH Down or Muriatic Acid, am I not just defeating the whole purpose of using hydrogen peroxide?

And finally, no matter what I use to bring the PH down, will this affect the CH?

Thanks so much for any advice you can offer.

[chem geek]

Adding acid won't change the CH.  You can only lower the CH via water dilution or by removing it with pre-filter you use when filling the spa with water (this is in effect an inline water softener that attaches to a hose) or by using a calcium removal product such as HotSpring Spa Vanishing Act Calcium Remover.

You should not use vinegar to lower the pH.  The purest acid you can add would be muriatic acid, but it is strong and fumes unless you get the half-strength (15-16%).  For spas, most people use dry acid (sodium bisulfate) which is the pH Down.  The only leftover from Muriatic Acid is chloride (i.e. salt) while from the dry acid it is sulfate.

So are your wife's chemical sensitivities so strong that she is unable to shower or bather without using a chlorine filter?  If not, then she really isn't as sensitive as you describe, at least not to chlorine.  If you were to start your soak with 1-2 ppm Free Chlorine (FC) and had Cyanuric Acid (CYA) in the water, then it would be less exposure than in a shower or bath with chlorine in the tap water.

If you use hydrogen peroxide, then for disinfection it needs to be at such as high level (usually 50 ppm or more) that it itself can be irritating to sensitive skin.  It is not EPA approved in the U.S., but is approved as a disinfectant in Australia.

[Quickbeam]

Thanks Chem Geek so much for your response. I was really hoping to hear from you on this. From what you are saying, I think I will try and find the half strength Muriatic Acid. That sounds like it would be best for our application.

As for my wifes’ chemical sensitivities, she is able to shower without a chlorine filter in our house but she just does not want to expose herself to any more chemicals than is absolutely necessary. She has been fighting this battle for three or four years now and just doesn’t want to take any backward steps. I should also point out that it is not only chemicals she has sensitivities with - there are a multitude of other items including many, many different food groups. She has gone through a lot with this, more than I can possibly describe here, and I certainly understand her reluctance to expose herself to any more chemicals than she needs to.

We have a friend who uses hydrogen peroxide as a sanitizer and we have both been in that tub with no adverse effect. In fact, we quite enjoyed the feeling - it left our skin soft and smooth feeling. So we know at least that the hydrogen peroxide should not have any adverse affects for her.

I do have one further question for you if you don’t mind. I am thinking that my CH at 210 is O.K., but I also know that in our house the tap water does leave calcium deposits. I notice it in our tea kettle, etc. One of the spa dealers I went to suggested I use a product called “Stain Control”. They told me it was a de-scaler and that I should add in 1/4 cup per week (our tub holds 340 gallons water). I was wondering if you think it is necessary for me to add this kind of a product to our tub? Given that we get calcium deposits in our tea kettle, etc., am I likely to damage the tub if I don’t add a de-scaler?

Thanks again Chem Geek. I really do appreciate you taking the time to answer me.

[Vinny]

I have used vinegar in a pinch to lower PH but wouldn't say I would do it all the time. I have used PH down when I went a little crazy trying to raise the PH and went too far; I have never used muriatic acid.

Have you looked into Baqua Spa? I personally have never used it as it is an expensive way to sanitize the water vs chlorine but it may be equivalent in cost to hydrogen peroxide.

[Quickbeam]

Thanks Vinny,

I'm not sure how much the hydrogen peroxide is going to cost us. I recently bought 5 gallons of 29% hydrogen peroxide for $50. I suppose I'll only know the true cost when I learn how long the 5 gallons lasts.

[Vinny]

Thanks Vinny,

I'm not sure how much the hydrogen peroxide is going to cost us. I recently bought 5 gallons of 29% hydrogen peroxide for $50. I suppose I'll only know the true cost when I learn how long the 5 gallons lasts.

Wow, that's a lot cheaper then I saw when I was looking on the internet ... it may be very economical to run! I was seeing 35% running about $125 for 4 gallons. It looks like you only use 1 cup of 35% peroxide at a time based on this website  http://purehealthsystems.com/hydrogen-peroxide-pool-spa.html  so depending on how long the peroxide lasts (chlorine doesn't last very long in hot water) you may have the 5 gallons for a while.

[Topline Mike]

Thanks Chem Geek so much for your response. I was really hoping to hear from you on this. From what you are saying, I think I will try and find the half strength Muriatic Acid. That sounds like it would be best for our application. 

If you use half strength acid, it will take twice as much to lower the pH.  The human eyeball has a pH of 7.5, so you are shooting for a pH of 7.2 to 7.8 for balanced water.  First you balance the water, then you add the sanitizer.  The sanitizer you choose will affect the water balance.  Having the taylor test kit is very important.  If you've read the thread about hot tub rash, "close enough" with test strips doesn't cut the cheese in my mind. 

[dunecritter]

Thanks Chem Geek so much for your response. I was really hoping to hear from you on this. From what you are saying, I think I will try and find the half strength Muriatic Acid. That sounds like it would be best for our application. 

If you use half strength acid, it will take twice as much to lower the pH.  The human eyeball has a pH of 7.5, so you are shooting for a pH of 7.2 to 7.8 for balanced water.  First you balance the water, then you add the sanitizer.  The sanitizer you choose will affect the water balance.  Having the taylor test kit is very important.  If you've read the thread about hot tub rash, "close enough" with test strips doesn't cut the cheese in my mind.

Ok...not to hijack but clarify...I own the taylor test kit as well as a few other reagent based testers and I do like them. It is accurate when compared to other reagent kits when I compare readings but just to clarify...The test strips are also right in check as well...I have never had a test strip give me a incorrect reading when compared to a reagent based kit...If someone has had a test kit differ from a test strip reading it was most likely= Read too late to where the colors bled, dried out and or diluted to much or possibly the strips were out of date and were "expired" Not sure but they do have an expiration date stamped on them. I have no color blind issues so I don't have any problems reading the strips but I have heard of others with this difficulty.
Regardless when a in date test strip is used and read within the allowed time they are in fact "close enough" and I've used this term in the past for a test strip so I'll run with that. Don't be afraid of using a test strip and not trusting it as its right there on accuracy. Using the test strip correctly is the key...Simply follow the instructions and you'll be fine. Mike you've owned your hot tub what??? 3 months now and it is your first hot tub if I'm reading your posts correctly. Have you ever even owned a test strip and tried them with conflicting results??? I bet not as others would agree. The reagent kits are best but strips work well also.  and are much more convenient. My reagent kits just sit on the shelf mostly and I use the strips regularly with normal results. That goes for all my hot tubs as well as my pool with over 24 years experience. Sorry Mike...Not to bash your post but it seems as though your giving the general public misrepresented negative feed on the test strips without actually owning or comparing them yourself. I have compared and I'm confident to claim they work well. I think its great that your an excited new hot tub owner and your enjoying all aspects as well as being on this forum to help and give your $.02 but lets try and keep it factual with true personal experience. If You indeed do own test strips and have personally compared with conflicting results I think you'd be one of the rare cases and I'm sure there's a reason.

I've always used dry acid (PH DOWN) with normal good results.

[Topline Mike]

I just laugh at the folks that tell me they've been doing things for "X" amount of years.  You can still be doing things the wrong way for so many years, just ask the Minnesota Vikings. 

I did get a test strip pack with my tub from the previous owner.  I posted this before, and my results were close. 

I can understand you using the test strips instead of the kit.  It's so convenient and quick. 

If you guys and gals want to use test strips, go get em.  I prefer a more accurate test kit.  I read about test strips vs. a test kit on another forum, and that's where I got my information. 

[chem geek]

I've used test strips for my pool to compare with the Taylor drop-based test kit and found that they do vary and are not always accurate and that is the experience for hundreds of pool owners reporting at other forums.  First off is that some of them do not measure high disinfectant levels.  Also, almost all of them measure Total Hardness which includes magnesium and do not measure Calcium Hardness which is relevant to predict scaling.  They tend to be worst off for measuring Cyanuric Acid (CYA) level and tend to be best at pH so long as disinfectant levels are not too high.  You can see a table of comparison in this post.  Clearly the strips are only an approximation given their broad ranges between patch/color levels.

Now that is not to say that under some conditions a fresh set of strips used properly will measure in their broad ranges consistently with an accurate drop-based kit.  So if one is interested in quick-and-dirty speed rather than accuracy, then if they've validated that their strips used with their water are in the ballpark, then you'll know what you are getting.

As for hydrogen peroxide, you can get 27% hydrogen peroxide in Baquacil Oxidizer (careful: NOT CDX) for $17 per gallon here and at other similar sources.  Remember to keep it cool and out of sunlight.

As for alternatives to halogen-based disinfectants, there is also Nature² which uses silver ions and uses non-chlorine shock (MPS) in combination.  However, MPS may be irritating to some, though probably not much different than hydrogen peroxide.  Also, one usually needs to use chlorine once every week or two to keep the water clear (you can't use another oxidizer with hydrogen peroxide since it also acts as a reducing agent).  As was mentioned, Baquacil is another alternative and it uses hydrogen peroxide as an oxidizer, but Baquacil is the disinfectant, so the hydrogen peroxide level is far lower in this system so should be even less irritating (but it's expensive).

[Quickbeam]

Thanks everyone for your replies.

I think I'm starting to get this figured out, but I do still have one lingering question (well I suppose two questions now given Topline Mike's post). The CH reading I got from my tapwater was 210. My owners manual says it should be anywhere between 150 - 250 and my dealer says anywhere between 175 - 350. Given this I'm thinking my CH is O.K. However, I know from experience that this same water in our house leaves calcium deposits. I can see it in tea kettles, etc. The question then is do I need to use some kind of de-scaler product, even though my readings are within the correct perimeters? One dealer told me I should add 1/4 cup per week of a product called "Stain Control" manufactured by I think Pure Spa. The dealer told me it was a de-scaler and would prevent calcium deposits. Am I going to damage the spa if I don't add this?

And secondly, Topline Mike said in his post that I first need to balance the water and then add the sanitizer, but that the sanitizer would affect the water balance. If this is the case, wouldn't it make more sense to add the sanitizer first and then balance the water, or am I missing something here?

As always, thanks so much for your help.

[dunecritter]

I prefer a more accurate test kit.  I read about test strips vs. a test kit on another forum, and that's where I got my information. 

Well there you have it....Read it on a public forum....Gotta be legit if its on the internet! LOL

[dunecritter]

Quickbeam, just make sure you give the tub some time after adding chemicals like PH Down to fully take effect...Best to take a reading 12-24 hours after adding the Dry Acid to bring down the PH.

[Quickbeam]

Thanks Dunecritter,

Does it make any difference if I balance the water before or after adding the sanitizer?

[dunecritter]

I would balance after sanitizer personally but remember you add sanitizer often with every use and shocking weekly and your levels of sanitizer will change very rapidly depending on what your using for a sanitizer and depending on if you are adding a stabilizer (CYA) and your PH levels will change at a much slower rate. Chemgeek is a wealth of water chemistry and I would follow his recommendations without hesitation over all. It's not rocket science and you should determine which route of sanitizer you want to use and stick with it. You will learn quickly and master that particular method and then it gets to be pretty simple. Keep it easy and enjoy your tub...your not going to have a melt down if your levels fall out of range for short periods of time...it just requires a little attention to bring it back in spec. ToplineMike is taking his water care very seriously kinda like a new hobby and a lot of others do as well.I guess I kinda did as well with my ACE system also but I choose to keep it simple and I have 24 years of owning tubs to prove it works for me. I personally have always used Chlorine granules and never a floater. I tried Bromine for a year with a new tub years ago and didn't really like it (Possibly because I never gave it a chance trying to learn a new procedure) so I went back to basic Chlorine. I now have the ACE salt system on my current personal tub and I never physically add any sanitizer. I just balance PH once a month if needed. Chemgeek has recommended that I add CYA to minimize outgassing to protect my cover and pillows but I have yet to do so because I want to experience what results I will get just like any of my customers that have also purchased the ACE on their HS tubs.