Tsp Effects

[Daniel Erlandson]

Cleaned my filters the other day with TSP and thought I had rinsed them well enough afterward, but when I put the filters back into the spa I got quite a bit of foaming at first and then the TA and dropped quite a bit. This was about a week ago and have been adding TA riser since then to get the TA back up. What happened here? I had read about using TSP to clean filters but never any associated effects. Guess I didn't rinse them well enough??

dan

[quantumchromodynamics]

The addition of trisodium phosphate Na₃PO₄ would add sodium and phosphate ions (PO₄^3-). About 66 % of the phosphate ions (PO₄^3-) would take up 1 hydrogen ion to form hydrogen phosphate (HPO₄^2-), and about 34 % would take up 2 hydrogen ions to form dihydrogen phosphate (H₂PO₄^-).

The addition of TSP would raise the pH and the total alkalinity.

Are you sure that it was real TSP? Most "TSP" is really a TSP substitute that contains sodium sesquicarbonate and sodium metasilicate, both of which will raise the pH and alkalinity.

The TSP (real or substitute) should not be the cause of your TA dropping. What further information can you provide? What are all of the readings for your tub and supply water? What chemicals have you added?

Calcium will combine with some of the phosphate to form insoluble calcium phosphate. Therefore, you could get a white precipitate, which would lower the calcium levels, but not the alkalinity. However, I wouldn't think that the amount of TSP that would be added from a rinsed filter would be enough to cause much problems.

The foaming could possibly be caused if the TSP was a substitute that contained surfactants.

[simonc]

I can't help you with the chemistry question ... why your TA is dropping ... but I can tell you how I use TSP to clean the filters on my spa. I don't have any foaming problems after cleaning the filters.

1. First off, I have two sets of filters. So I can have a clean set already to put in when I need to change them.

2. Read the cautions on the TSP package. It's a powerful chemical and can be dangerous if you don't handle it properly.

3. I have a large plastic storage-type bin. I put in about 10-15 gallons of water which is enough water to cover the filters completely. Then mix in 2 cups of TSP. I also add a cup of bleach. Stir it up and then put in the filters.

4. I let it sit for a day.

5. I pull the filters out. I rinse them down real well with a spray nozzle on the hose.

6. After throwing away the old TSP water. I rinse out the tub and refill it with clean water. I then put the filters in. Move them around a little and then let them sit another day.

7. I take the filters out. Hose them down with the sprayer. Throw out the old water, put in new water, and let them soak another day.

8. Lastly, I take out the filters and hose them off again. This time I let them dry so they are ready for use.

I think using the plastic tub reduces the amount of water I need to use. The tub soaking dilutes the residual TSP. By repeating the process the TSP residual is very very low and I don't have any foaming problems.

Lastly, I don't change my filters very often - maybe every two or three months. I know some people change their filters every week. I wouldn't use the above process (too much TSP, too much water, and too much work) if I changed them often.

I hope this helps,

- Simon

[Daniel Erlandson]

thanks for the responses,

I am using well water and a simple 4 parameter Aquachek test strip: pH, FC, TA and Stabilizer. TA on fill was in the ok zone ( I believe) which is 80-120 pH was also ok. Did Dichlor for a few days until the Stabilizer went up and then switched over the Bleach. I have shocked twice with MPS. On the day in question I soaked the filters in TSP for a few hours, rinsed them (probably not well enough) and on reinstallation noticed a lot of foaming. My FC was low at that time so I decided to add some dichlor thinking it might help clear up the water. After some time I also added some MPS thinking that maybe the foaming was due to dislodged organics that I hadn't rinsed off. I think that was when I tested the water and found it low in pH and TA (super high with FC). Have managed to get the TA and pH back up with TA rise (sodium carbonate?).

Next time I clean the filters (just have one set for the moment) I'll try simonc's method and see what happens. Have got to come up with a good rinsing/soaking set-up for the inside, for when the weather gets colder and I turn off the outside hose bibs.

dan

[quantumchromodynamics]

Both dichlor and MPS are acidic and will lower your pH and TA. Test strips are just not accurate or reliable. You need to get a good test kit. TA increaser is sodium hydrogen carbonate (aka sodium bicarbonate or baking soda).

Here is a source for real TSP.

And while you're at the chemistry store, you might want to pick up enough boric acid to add 50 ppm of borates.

3.8 ounces weight of boric acid per 100 gallons of water will increase borates by 50 ppm. A 420 gallon tub would take 1 pound of boric acid. 7 pounds costs $13.44 and will do 7 fills. That's only about $2.00 per fill.

[Hillbilly Hot Tub]

Both dichlor and MPS are acidic and will lower your pH and TA. Test strips are just not accurate or reliable. You need to get a good test kit. TA increaser is sodium hydrogen carbonate (aka sodium bicarbonate or baking soda).

Here is a source for real TSP.

Di-chlor itself is not acidic, it has a PH of 7.0, the act of it oxidizing wasted creates an acid.

[quantumchromodynamics]

Di-chlor itself is not acidic, it has a PH of 7.0, the act of it oxidizing wasted creates an acid.

NaC₃Cl₂N₃O₃ + 2H₂O < > Na⁺ + C₃H₂N₃O₃^- + H⁺ + HOCl + OCl^-

As you can see, there is an extra hydrogen ion on the right. That means that dichlor is acidic upon addition. At a pH of 7.5, about 20 % becomes C₃H₃N₃O₃, and about 80 % becomes C₃H₂N₃O₃^-. pK1 = 6.88, pK2 = 11.40, pK3 = 13.50

In addition, dichlor does not have a pH. pH is only measured when the dichlor is dissolved and depends on the concentration. The given pH for a 1% solution is 6.0 to 6.5, which is acidic. Even a pH of 7.0 is acidic when compared to the normal pH of properly balanced water.

pH: 6-6.5 (1% solution)

http://www.protechpoolsupplies.com/Support-Docs/MSDS/Dy-Chlor-II-MSDS.pdf

There is no question that using bleach is pH neutral while using Dichlor is acidic

[chem geek]

We're being picky here. For practical purposes, adding Dichlor barely touches the pH in buffered water. Even with a low TA of 50 ppm (and CYA of 30 ppm), adding 10 ppm FC of Dichlor only lowers the pH from 7.5 to 7.42 so not very much. However, if all of this chlorine were to oxidize bather waste, then the pH would drop to 7.0. This is part of the reason why 50 ppm Borates would be useful when the TA is low -- in this case, the pH would drop to 7.22. Of course, one usually doesn't see such a dramatic drop because there is carbon dioxide outgassing compensating for this and having the pH rise or at least not drop as much.

[quantumchromodynamics]

Even with a low TA of 50 ppm (and CYA of 30 ppm), adding 10 ppm FC of Dichlor only lowers the pH from 7.5 to 7.42 so not very much.

32.32 grams of dichlor in 470 gallons of water will raise the FC by 10 ppm. And, 32.32 grams of dichlor creates the same number of moles of hydrogen ions as 10 milliliters of 31.45 % muriatic acid. Therefore, they should be equivalent in their effect on pH.

According to the pool calculator, the addition of 10 ml of muriatic acid to 470 gallons will result in a pH drop of 0.17. If the starting pH is 7.5, then the pH should drop to 7.33.

[chem geek]

32.32 grams of dichlor in 470 gallons of water will raise the FC by 10 ppm. And, 32.32 grams of dichlor creates the same number of moles of hydrogen ions as 10 milliliters of 31.45 % muriatic acid. Therefore, they should be equivalent in their effect on pH.

According to the pool calculator, the addition of 10 ml of muriatic acid to 470 gallons will result in a pH drop of 0.17. If the starting pH is 7.5, then the pH should drop to 7.33.

You are forgetting that the hypochlorous acid that is produced is a weak acid, not a strong acid, so you can't count it the same as adding the equivalent number of moles of hydrochloric acid. The pH drop is equivalent to 2.36 ml of 31.45% Muriatic Acid. 10 ml would lower the pH from 7.5 to 7.25. The Pool Calculator uses approximations for the acid/base calculations, especially in the "Effects of Adding Chemicals" section that makes assumptions about the TA level (not the 50 ppm I was using). If you want accurate calculations, use my Pool Equations spreadsheet.

[waterbear]

Guys,

this advanced chemistry has gotten so far away from the OP's question and is so technical that I can see OP's eyes glaze over from here!

I suspect that a TSP substitute was used that contained sufactants and I urge the OP to read the label and post the ingredients so we can know what ACTULLY happened.

Also, the OP is using test strips so all the test results are basically bogus! I also suspect that FC is low and CYA is high as a normal condition.

I also suspect that when the low TA was read FC was high and the strip was bleaching out.

OP, how close to the mark am I?

[Daniel Erlandson]

Don't mind all the chemical minutia. I'll learn something in the end...the tsp is Red Devil brand TSP/90 substitute...no phosphates. Label says sodium metasilicate. Wrong stuff to use I'm guessing.

[quantumchromodynamics]

I suggest that you get real TSP from the chemistry store. You could also get boric acid at the same time to add 50 ppm of borates.

http://www.chemistrystore.com/

http://www.chemistrystore.com/search.cgi?keywords=trisodium+phosphate

http://www.chemistrystore.com/search.cgi?keywords=boric+acid

I also strongly recommend a good test kit, such as the Taylor K-2006

http://www.amatoind.com/taylor-k2006-test-p-555.html

[Dnepr Dave]

I enjoyed the chemistry discussion also.

Dave