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SWIMMING POOLS
pH / ALKALINITY
pH & Swimming Pools (3/9/99)
What Causes High TA (3/9/99)
High pH In Newly Replastered Pool (8/18/98)
Explanation of pH and Alkalinity (8/3/98)
Low pH (7/15/98)
Low pH / pH Of Zero? (5/28/98)
Raising Pool pH (5/11/98)
Lowering Pool Alkalinity w/o Changing pH (5/4/98)
PH Balance / Switching To Chlorine In Spa (5/1/98)
Increasing / Decreasing PH In Pool Water (4/27/98)
Adjusting PH and Total Alkalinity (4/1/98)
pH & Swimming Pools (3/9/99)
Q:
My son is doing a research paper on pH testing and I thought you could give us some basic information on why pH levels are important in swimming pools, what causes them to vary, what does the water feel like with high/low pH levels, what is used to test and how do they work, etc. Any help you could give would be appreciated!!!
M.A. - Germantown, TN
A:
Control of the pH is important for several reasons. The accepted optimum pH of 7.2 - 7.6 , for pools utilizing chlorine, is a compromise based of these several factors.
Acidic water (below 7.0) can, as the pH drops become increasingly more corrosive to metal and masonry parts. The optimum range is slightly alkaline in order to avoid corrosive effects. In addition, low pH can make chlorine more aggressive and, therefore, more irritating.
High pH water (over 7.6) can lead to scale formation or cloudy water under certain circumstances. Many minerals present in water become less soluble as the pH rises. The efficiency of chlorine decreases as the pH rises. In the 7.2-7.6 range, chlorine has reasonable efficiency. At a pH of 8.0 it decidedly less effective. At a pH of 9.0. Chlorine is ineffective as a pool water sanitizer.
The pH of the eye is approximately 7.6. For bather comfort, pH maintained in the optimum range as recommended. Water left to nature will have an acid pH, based on the absorption of carbon dioxide and other acid gases. The various chemicals added all make a contribution to the pH. Some forms of chlorine are high pH -- others are low pH. Ultimately maintaining the pH is a balancing acts that must take into consideration all of the factors. Acid water can feel drying. High pH water can feel slippery. This is based on extremes not expected in a pool.
I hope that I have been helpful.
Good luck.
Alan
What Causes High TA (3/9/99)
Q:
I was wondering if you could tell me what causes a high T/A. We have a indoor/inground 16X32 ft pool. Up until recently everything was fine. During X-mas we got green algae. Since that time the T/A is up around 270-290ppm. I have been following the advise of our dealer, but we are beginning to wonder what is going on. After eliminating the green algae and installing a new sand filter I have been adding dry acid to bring the T/A down. It is not working. I have even put 1 ft of fresh water in the pool, under the advice of the dealer. The T/A is still climbing.
G.L. - Saskatoon, Saskatchewan, Canada
A:
The high TA is probably due to the chlorine being added on a regular basis. Calcium, sodium or lithium hypochlorite are all very alkaline and will boost the TA and pH. If the pool is gunite the walls may be part of the problem -- especially if the calcium level is less than 200 PPM.
A foolproof way of lowering the TA without overshooting or ending up with a low is pH is to add dry acid daily. I suggest adding 2 pounds daily until the pH drops to 7.2 or the TA is in range. At this point you should be able to control it as needed.
If the pH is high -- the chlorine is less efficient. This could explain the algae. If the water is clear and the pH is in range there is no compelling need to have a TA in range. A high TA under these circumstances is not necessarily a problem.
I hope that I have been helpful.
Sincerely,
Alan
High pH In Newly Replastered Pool (8/18/98)
Q:
My pool was recently replastered and I am having a terrible time keep the ph in range. It constantly goes to 8 and above. What do I have to do?
G.G. - Phoenixville, PA
A:
The pH is rising because the minerals in the plaster are dissolving in the water. To help prevent this or at least slow it to a manageable level, do the following:
Adjust total alkalinity to 80-120 PPM
Adjust calcium hardness to 150-200 PPM
Maintain pH in 7.2-7.6 range.
Depending upon the type of chlorine that you are using, the addition of chlorine may push the pH in one direction or another. This will require periodic additions of pH control chemicals.
I hope that I have been helpful.
Sincerely,
Alan
Explanation of pH and Alkalinity (8/3/98)
Q:
What is it that we are trying to do when we add chemicals to raise the Total Alkalinity? How can the pH be in range and yet need to increase alkalinity? Isn't pH a measure of alkalinity/acidity? Also, when we add the TA increaser we get white scale near the waterfall. What causes that?
D.H. - Melbourne, FL
A:
pH is a measurement of the acidity or alkalinity of the water. 7 is neutral. Low readings are acid. High readings are alkaline.
Total alkalinity is a measure of all the alkaline materials present in the water. A low t/a will cause wild fluctuations in pH. Higher t/a can help stabilize the pH and make control easier. Very high t/a can make it difficult to raise or lower the pH.
The white scale is probably calcium carbonate. Raising the pH and t/a will make calcium less soluble in water and can lead to scaling.
Try to maintain the pH at 7.2-7.6, the t/a between 80-120 PPM. This usually avoids scale formation below 400 PPM of calcium hardness. Adding SUN Stain and Scale control can help avoid problems.
I hope this information is helpful.
Sincerely,
Alan
Low pH (7/15/98)
Q:
My husband and I are struggling this year with our pool. The ph will NOT go up and/or stay in the 7.2 or above range. It stays somewhere around the 6.8 and below range. The total alkalinity is anywhere from 240-300 ppm. The pool is clear, the chlorine seems very high when tested. (we use test strips, and poolmaster chemistry kit-tests: ph, chlorine, residual chlorine, acid and alkalinity) There is a strong smell of chemicals when we open the electric cover, as well as when we are in the pool moving the water around. The gasses seem to hover at the top of the water.
My understanding is that if the alkalinity is off, the ph will not stay in range, so we tried to lower the alkalinity and then we are to adjust the ph..... We are already experiencing eroding brass fittings in the heater.
This is, by the way a 4 year old vinyl pool that holds 40,000 gal. It is kept very clean and maintained well, except for this chemical disturbance, which I know is a bad situation. We have not ever had this sort of problem before.
A.R. - Aberdeen, SD
A:
Everything you mentioned confirms a low pH. The odors and the corrosion!!!!!!!
Most pools have total alkalinity based on carbonates. I would hazard a guess that in your case the source water is high in dissolved minerals, other than carbonates.
A high total alkalinity means that more chemicals are required to move the pH up or down.
I suggest that you raise the pH to 7.2-7.6 before further damage is done to the heater. So long as the water is clear and the pH is in range, I would not be concerned with the high TA. I would avoid using products containing calcium, in order to keep the hardness from rising.
I hope that I have been helpful.
Sincerely,
Alan
Low pH / pH Of Zero? (5/28/98)
Q:
We have a 24' above ground pool. We have just recently opened the pool and had water added. I have checked the PH level and it registers at 0. I have added lots of PH additive, and cannot bring the PH level up. How much more PH increaser should I add and what is the danger in the PH being too low?
P.H. - Eaton Rapids, MI
A:
Your pH is not 0. Is probably lower than whatever value is on your test kit, but it is not 0. It is also possible that your testing materials have gone bad.
If your pH is low, it is important to raise the total alkalinity as well. This will help stabilize the pH and make control easier. Low pH creates corrosive and irritating conditions.
My recommendation is that you bring in water sample to a local pool professional for a complete water analysis. This will help confirm the accuracy of your tester and help get you on the right track.
I hope that I have been of assistance.
Sincerely,
Alan
Raising Pool pH (5/11/98)
Q:
Any suggestions on raising ph? The level is at 6.7. We have a 38,000 gal indoor gunite pool.
Paul - Lincoln Park, MI
A:
What's causing the low pH?????????
It could be damaging your heater, if there is one. In order to help keep the pH in range, it is necessary to have a total alkalinity in the 80-120 range. It seems certain that your T/A is too low. Test water for T/A and add approximately 6 pounds of Total Alkalinity Booster for each 10 PPM increase that is needed. This is based on your size pool. After adjusting the T/A, retest the pH and if necessary adjust with the appropriate pH control product. Retest pH and Chlorine frequently to help maintain optimum conditions.
I hope this will solve the problem.
Sincerely,
Alan
Lowering Pool Alkalinity w/o Changing pH (5/4/98)
Q:
Alkalinity of my pool is about 200 ppm. I've already had to add acid to lower the pH to the right range. How do I lower the alkalinity without changing the pH?
R.G. - Boise, ID
A:
Whenever you add acid to lower the pH, you will lower the Total Alkalinity as well. The reverse is also true.
If your pH is 7.2 - 7.6 and there are no signs of cloudiness or scaling, due to high hardness, the fact that your total alkalinity is too high should not present a problem.
If you want to lower the T/A, add 1 pound of pH MINUS or 1 pint of Muriatic Acid per 10,000 gallons per day so long as the pH is above 7.2. Stop when the pH reaches 7.2 or the T/A reaches 120 PPM. This method will prevent overshooting the mark.
I hope that this information will prove helpful.
Sincerely,
Alan
PH Balance / Switching To Chlorine In Spa (5/1/98)
Q:
We have an 18'x36' inground pool with an earth filter. We use chlorine and the water stays crystal clear, however we have a problem with acid balance and Ph. Also we want to change our hot tub to chlorine is there a problem?
PS - In the pool we used Baquacil for two years and was not satisfied.
G.N. - Berea, KY
A:
Water, has a tendency to drop in pH due to absorption of carbon dioxide and the effects of acid rain. If you are using a trichlor tablet as a chlorine source, it will also add acid materials to the water. In order to keep the pH in a 7.2 - 7.6 pH range with a minimum of difficulty, it is necessary maintain a total alkalinity of 80-120 PPM. In addition, if you are using trichlor tablets you should add some pH Plus each time you add tablets to the feeder. This will cancel the pH lowering effect of the trichlor.
In as much as you didn't tell what sanitizer you currently use in your spa, I will assume it is bromine or Baquacil. In either case things might go a lot simpler if you drained the spa. This should be done periodically in any event. The only chlorine suitable for spa use is sodium dichlor.
I hope that I have been of assistance.
Sincerely,
Alan
Increasing / Decreasing PH In Pool Water (4/27/98)
Q:
Can you express the reaction that takes place when you add chemicals to increase or decrease the pH level your pool water as a formula? If so, do you know what it is? Is the pool water expressed as H2O or because it already contains chemicals is it expressed differently?
T.P.
A:
The chemical reaction controlling the pH is: H+ + OH- yields H2O.
The actual pH of the water depends upon the relative concentrations of the H+ and the OH - ions. Acid solutions have more H+ ions. Alkaline solutions have more OH- ions.
Water is always H2O, even if there are dissolved salts. Chemical reactions of the dissolved salts may be listed separately. Adding pH Plus chemical to the water adds a source of OH-, causing the pH to rise.
Adding pH Minus chemical adds H+, causing the pH to lower.
I hope that I have answered your questions.
Sincerely,
Alan
Adjusting PH and Total Alkalinity (4/1/98)
Q:
I can never get my PH adjusted correctly. I have a new vinyl pool and when I get the alkalinity correct the PH is to high when I bring the PH down so does the Alkalinity. Any suggestions?
T.B. - Lewisville, TX
A:
It is more important to have a correct pH than it is to have a correct Total Alkalinity. Lowering the T/A will have a lowering affect on the pH. At first the pH will appear to drop only to rebound later. This is due to the presence of carbon dioxide in the water.
If your T/A is too high add small amounts of pH Minus, 1 pound per 10,000 gallons per day, until the T/A is in range. DO NOT ADD ANY pH MINUS IF THE pH IS NOT ABOVE 7.2. A high T/A is OK so long as the water is clear and the pH is in range.
I hope that I have been helpful.
Sincerely,
Alan |
