Sandpaper hot tub?

[roberto1]

Thanks James!

That information is what I was hoping to get!
I'm going to turn down the water temp as much as I can, with out it freezing(I do live in Canada). With adjusting the pH down, the scale does seem to be getting less, although it doesn't seem to want to stay down.
Out of curiosity, why don't I want the pH to go below 7.2?

Thanks so much,
Rob

 

[roberto1]

Is there more I should know?

 

[JamesW]

Going too low with the pH can risk damaging the tub and equipment. Also, once you go below 7.2, you usually lose the ability to know how low the pH is unless you have a pH test that is designed to measure below 7.2.

The reason that the pH tends to go back up is that the high TA is forming carbon dioxide, which off gasses and raises the pH. Also, as the scale dissolves, it will cause the pH to rise even more.

Keep lowering the pH as often as necessary to keep it down to 7.2 and that will lower the TA. Eventually the TA will get low enough that the pH will stop rising. As the TA gets below 50 ppm, the amount of acid it will take to lower the pH will decrease. Therefore, you will have to reduce the amount of acid you use to prevent the pH from going too low.

You can use the pool calculator to calculate the CSI (Calcite Saturation Index) by putting in the pH, TA, Calcium Hardness, Cyanuric acid, Borate and temperature. The lower you can get the CSI, the faster the scale will dissolve. In the future, you can use borates to reduce the rate of pH rise and reduce the risk of scaling.

In the future, keep the CSI below 0.0 to prevent further scaling events.

 

[roberto1]

James, you da man.
Once again, thank you

Okey Dokey, I'll keep on top of the pH. It does seem to be getting less sandpapery in the spa.

What about the FC? It's sky rocketed way off the charts. It's supposed to be yellow but its a crazy orange colour now.
Should that just dissipate?

Rob

 

[JamesW]

What chlorine is being added to raise the FC? It would be best if you were using an FAS-DPD test kit for better accuracy, such as the one that comes in the TF-100 test kit, or as a stand alone kit.

If you want to lower the FC, you can use 0.83 ounces (volume) of 3% hydrogen peroxide per 400 gallons of tub water to lower the FC by 1 ppm. Or, you can use 0.0544 ounces (weight) sodium thiosulfate pentahydrate per 400 gallons of tub water to lower the FC by 1 ppm.

 

[roberto1]

What chlorine is being added to raise the FC? It would be best if you were using an FAS-DPD test kit for better accuracy, such as the one that comes in the TF-100 test kit, or as a stand alone kit.

If you want to lower the FC, you can use 0.83 ounces (volume) of 3% hydrogen peroxide per 400 gallons of tub water to lower the FC by 1 ppm. Or, you can use 0.0544 ounces (weight) sodium thiosulfate pentahydrate per 400 gallons of tub water to lower the FC by 1 ppm.

That's the funny thing...I'm not adding any chlorine. It's just increasing as I've been adjusting the pH down.
I bought the TF-100 test kit so I'll try that test. I was just using the liquid based test kit that tests for pH and FC and was surprised to see the FC increase so much.

Cheers,
Rob

 

[JamesW]

Do you think that you might have accidentally added bleach instead of acid on one or more occasions?

Are you using liquid muriatic acid or dry sodium bisulfate to lower the pH?

What is happening to the TA?

How do you usually add chlorine?

With the FC so high, the pH will test higher than it is. Therefore, you need to get the FC down before you can get a reliable pH test.

 

[roberto1]

Do you think that you might have accidentally added bleach instead of acid on one or more occasions? No, I at this point I haven't switched to the BBB method....I've only used Lithium to add chlorine.

Are you using liquid muriatic acid or dry sodium bisulfate to lower the pH? I was using pH reducer and ran out of that, now I'm using liquid muriatic acid.

What is happening to the TA? I'm going to check first thing in the morning.

How do you usually add chlorine? Lithium

With the FC so high, the pH will test higher than it is. Therefore, you need to get the FC down before you can get a reliable pH test.

Okey Dokey. I'll have to get some supplies tomorrow, looks like...

Thanks for sticking with me on this.... :-D
Cheers,
Rob

 

[roberto1]

OK I picked up some Hydrogen peroxide this am and got my FC down.
It's now 1 or so...I'll add some bleach to bring it back up a bit.
pH is 7.2
T/A is 40
CH is 140 (I find this hard to read... it turns kind of purpley with red specs in it and I'm not sure how to read it exactly)

Should I bring up the T/A now or leave it where it's at until the scale is dissolved?

The Spa seems to be getting better and better in terms of the roughness.
Should I also go in with a nylon brush and loosen up the scale?
Thanks,
Rob

 

[JamesW]

Don't raise the TA. Just keep the pH at 7.2, and the scale should begin to dissolve. It probably won't completely dissolve, so you will probably need to use some distilled white vinegar or scale remover (make sure that it says that it is safe to use on acrylic) when you drain to remove the remaining scale.

A nylon brush would probably help, and should probably be safe, but it might scratch the finish a little, so you will have to decide if you want to try it. If scale gets caught in the bristles, it could cause scratches.

The calcium test sounds like there is some sort of interference, probably due to metals, such as copper and/or iron. Add 5 drops of the titrating reagent (the one where you add drop by drop until the color changes.) to the sample first, and then run the test as normal. Be sure to count the 5 drops of titrating reagent in the total number of drops needed to change the color from red to blue.

 

[roberto1]

Don't raise the TA. Just keep the pH at 7.2, and the scale should begin to dissolve. It probably won't completely dissolve, so you will probably need to use some distilled white vinegar or scale remover (make sure that it says that it is safe to use on acrylic) when you drain to remove the remaining scale.

A nylon brush would probably help, and should probably be safe, but it might scratch the finish a little, so you will have to decide if you want to try it. If scale gets caught in the bristles, it could cause scratches.

The calcium test sounds like there is some sort of interference, probably due to metals, such as copper and/or iron. Add 5 drops of the titrating reagent (the one where you add drop by drop until the color changes.) to the sample first, and then run the test as normal. Be sure to count the 5 drops of titrating reagent in the total number of drops needed to change the color from red to blue.

The scale has dissolved quite a bit. I was impatient and scrubbed the tub with the nylon brush this afternoon. It didn't seem to scratch much. The water was a bit cloudy after that for a couple of hours but it's clear again now.

How long would be best to leave the tub like this with low TA and pH of 7.2 with low temp?
I am concerned about the scale build up on the heater and internal plumbing.
Anything else that would be helpful? (I'm thinking I will clean it with some distilled white vinegar when I drain, as you have suggested.)

Cheers,
Rob

 

[JamesW]

You can probably drain and refill now. Once you refill, keep the pH down to about 7.4 and the TA as low as necessary to keep the pH from rising too much. The TA will probably need to be kept between 40 and 60 ppm. Don't add any calcium; you want the calcium as low as possible. Adding 50 ppm borates would be helpful. I would use boric acid to add the borates.

There is not much you can do about the heater element being scaled. Elements eventually burn out anyway. Yours will probably burn out just a little bit early. You could remove it and try to clean it, but it's probably not worthwhile to do so.

Make sure to clean the filter element.

 

[roberto1]

You can probably drain and refill now. Once you refill, keep the pH down to about 7.4 and the TA as low as necessary to keep the pH from rising too much. The TA will probably need to be kept between 40 and 60 ppm. Don't add any calcium; you want the calcium as low as possible. Adding 50 ppm borates would be helpful. I would use boric acid to add the borates.

There is not much you can do about the heater element being scaled. Elements eventually burn out anyway. Yours will probably burn out just a little bit early. You could remove it and try to clean it, but it's probably not worthwhile to do so.

Make sure to clean the filter element.

Where can you get boric acid at? I have some Borax and Muriatic acid, would that be OK?

I drained and filled the tub, there was a significant amount of gritty scale that I cleaned out.

Thanks,
Have a great day
Rob

 

[JamesW]

You can use Borax and muriatic acid. However, I prefer to use boric acid.

http://www.chemistrystore.com/search.cg ... boric+acid

http://www.dudadiesel.com/search.php?query=boric

A 420 gallon tub takes 1 pound of boric acid to go from 0 to 50 ppm of borates. You should get enough to do several fills of the tub.