Raising ph in a swim spa pool

[Wolke]

I have a 2,000 gallon swimspa pool. The ph is always low. I'm not sure how much baking soda to add at a time before waiting an hour and retesting. I know for the spa side I add one ounce for the 450 gallon hot tub. Thanks so much for any help with this issue.

[waterbear]

Some more information would be helpful. How are you testing? What is your total alkalinity. What sanitizer are you using? (My guess is either trichlor or dichlor. Baking soda is used to raise Total alkalinity, not pH. However, if the TA is low and you are using triclor or dichlor that could explain your low pH. Sodium carbonate is best for raising pH when TA is low. Borax is best for raising pH when TA is in normal range.

If you would post a full set of test results and your testing method we can take it from there.

[Wolke]

I'm using a test strip. The alkalinity is fine 80-120. The ph is always around 6.8 I use dichlore (Spa 56 (99%)) to sanitize.)I'm actually using alkalinity increaser...sodium bicarbonate because I was told it would level out the ph.  I haven't tried baking soda yet. 

Thanks so much for any help you can give me with this.

[waterbear]

Alkalinity increaser is sodium bicarbonate is sodium hydrogen carbonate is baking soda. Save yourself some money and just get baking soda.

16 hours ago, Wolke said:

I'm using a test strip. The alkalinity is fine 80-120. The ph is always around 6.8 I use dichlore (Spa 56 (99%)) to sanitize.)

No, The alkalinity is not fine. FIne is not a reading. Strips are notoriously inaccurate and do not have the precision needed to balance water. When using an organic chlorine source (trichlor or dichlor) you are essentially always adding acid since they have an acidic pH (acidic on application and acidic reaction when they sanitize). This means that you need to run your total alkalinity in the 100 to 120 ppm range or possibly a bit higher. This requires a test that will give you a 10 ppm resolution on the test, not a 40 ppm resolution.. My suggestion is to invest in a Taylor Technologies K-2006 test kit. It will test all the parameters you need to test and is worth every penny. Don't try to save a few dollars with the K-2005. The K-2006 uses FAS-DPD testing which has several advantages over the DPD method used in the K-2005.

https://www.taylortechnologies.com/en/page/231/k-2006-complete-kit-with-fas-dpd

A bigger concern when using exclusively dichlor is overstabilization. Do you know your cyanuric acid (stabilizer) level? Dichlor adds 9 ppm cyanuric acid for every 10 ppm free chlorine added and this can quickly over stabilize the water which essentially inactivates the chlorine. It is sometimes referred to as 'chlorine lock' and the only cure is to drain and refill to bring the stabilizer level down only to repeat the process again. Switching to an unstabilized chlorine source sis a better idea. My recommendation is sodium hypochlorite (liquid chlorine or plain, unscented chlorine laundry bleach). Unsttabilized chlorine sources (sodium hypochlorite, lithium hypochlorite, and calcium hypochlorite) are essentially pH neutral. They are alkaline on addition and have an acidic reaction when they sanitizer. They require running the alkalinity lower, ususally around 60 to 90 ppm depending on the amount of aeration from jets, water features, ozone, and salt water chlorine generators present in the system. Once again, strips do not have the precision for determining this.

Here are some posts that might be helpful:

https://www.poolspaforum.com/forum/index.php?/topic/52523-some-truths-about-ph-and-ta/

This post explains how total alkalinity works:

https://www.poolspaforum.com/forum/index.php?/topic/28846-lowering-total-alkalinity-howto/

This post is on the dichlor/bleach method and, although they apply to spas can also be used in a swim spa:

https://www.poolspaforum.com/forum/index.php?/topic/23090-dichlorbleach-method-in-a-nutshell/

 

[Wolke]

7 hours ago, waterbear said:

Your post is so helpful, and I completely regret buying a swim spa. I'm obviously way in over my head with this. One question I have is, does all this information still apply if I have a UV Sanitation system? I'm going to drain the pool and start again, and I want to do it right the next time around.

 

 

[waterbear]

You are not in over your head. It's just a learning curve and your experience is very common.

Here is what I suggest:

1 Get a Taylor K-2006 (Amazon or an online pool supply retailer. Most pool stores do not carry it in my experience.

2 test your water (watch the videos in the link I provided to Taylor Technologies to learn how)

3. post your results here. We can then determine your next step and help you balance your water. . Since you said you are using dichlor it means you are not opposed to daily dosing of chlorine. My suggestion is to get your Cyanuric acid level in the 30 to 50 ppm range and dose daily with liquid chlorine or bleach to mainain a 3 to5 ppm Free Chlorine reading. I am suggesting a slightly higher Cyanuric acid levll than the post on the dichlor/bleach method because I am assuming your swim spa is not covered and exposed to sunlight.

4. UV sanitizing doesn't do much , IMHO, since it only sanitizes the water in contact with the bulb in the reaction chamber. It might also generate some ozone (depending on the type of UV bulb) but ozone is an oxidizer, not a sanitizer. UV is not a residual sanitizer which means it does not stay in the water to sanitize matter introduced by bathers and swimmers. FWIW, every bather introduces fecal matter, urine, and sweat (chemically very similar to urine) no matter how clean they THINK they are and there needs to be a fast acting RESIDUAL sanitizer in the water to handle this. Chlorine, Bromine, and Biguinide/Peroxide do this.

[Wolke]

Thank you for all the information you've given me. I did order the test kit you suggested. I won't have it until the weekend. In the meantime, the water is clear now. 

I do have an indoor swimspa, and I keep it covered when it's not in use.

 

 

[waterbear]

16 hours ago, Wolke said:

I do have an indoor swimspa, and I keep it covered when it's not in use.

In that case your UV will help break down chloriaimines (combined chlorine). However you will need to superchlorinate or possibly shock with MPS if you have persistent combined chlorine higher than .5 ppm. You will need to leave it uncovered when you do this to allow the volatile oxidation byproducts to outgas. Once we have good test results we can see exactly what is needed. Does the location of the swimspa have good forced ventilation? Air quality is a factor for indoor pools and spas.

In the mean time review the videos on the Taylor Technologies website that I posted ablve to learn how to use your kit properly and when you test chlorine use a 10 ml sample size  for a resolution of .5 ppm and a 25 ml sample size for the TA and CH tests for a 10 ppm resolution.