extremely low ph

Chlorinating, maintaining the right chlorine levels,
chlorine problems. Dichlor, trichlor, cal hypo, bleach,
granules, chlorine pucks and chlorine sticks.
jdstock

extremely low ph

Postby jdstock » Mon 22 Sep, 2008 11:51

I live in a villa in the UAE and pool maintenance is done by the staff so I have never worried about the readings. I bought a cheap kit just to check clorine level and found it was out of range ovr 4. Ph was also off the scale at less than 6.8. I took a sample to work to check with PH meter and reading was 4.0 which has me scared. The maintenance people have been using chlorine pucks so that is where the acid is coming from. I am going to buy a Taylor 2006 kit as per your recommendation. We have stopped using the pool and have removed the pucks. Is the water salvageable or do I need to start over?pool size is approx 10,000 gallons.


chem geek
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BBB method for pool care

Postby chem geek » Mon 22 Sep, 2008 13:23

Add a product to raise the pH right away. Most pH Up products are sodium carbonate, but that may raise your TA too high, though you can certainly add some to start with. If you have Borax, you can add that to raise the pH with less of a rise in TA. If you have lye (caustic soda), then you can pre-dissolve it in a bucket of water and then add that to the pool. You can use The Pool Calculator to roughly figure out dosages though for pH adjustment the calculator is approximate.
jdstock

Re: extremely low ph

Postby jdstock » Fri 26 Sep, 2008 07:56

jdstock wrote:I live in a villa in the UAE and pool maintenance is done by the staff so I have never worried about the readings. I bought a cheap kit just to check clorine level and found it was out of range ovr 4. Ph was also off the scale at less than 6.8. I took a sample to work to check with PH meter and reading was 4.0 which has me scared. The maintenance people have been using chlorine pucks so that is where the acid is coming from. I am going to buy a Taylor 2006 kit as per your recommendation. We have stopped using the pool and have removed the pucks. Is the water salvageable or do I need to start over?pool size is approx 10,000 gallons.


I added approximately 1 1/2 gallon of 48% caustic soda and the PH went too high. Currently it is 9.8. according to the Pool calculator I needed more than 10 gallons. Why did this change so fast?
I bought a poolcheck kit (Unfortunaately a Taylor kit was not available)and my readings now are as follows:
PH 9.8
CAL 400
CALC 150
Alk 125
Cl
Cyanuric Acid >200
Do I have any option other than dump and refill?
Guest

Re: extremely low ph

Postby Guest » Tue 30 Sep, 2008 16:53

I'm sure chem geek will get back to you. Until he does let me mention a few things.

If the CYA is really over 200 then drain and refill is the way to go. If this is an inground pool, be careful with the draining. Drain some and then refill and then repeat. Draining all at once can be a problem if the water table is high.

I would test the fill water to see what the levels are. That should give you an indication of what adjustments you'll need to make as you refill.

jdstock wrote:
jdstock wrote:I live in a villa in the UAE and pool maintenance is done by the staff so I have never worried about the readings. I bought a cheap kit just to check clorine level and found it was out of range ovr 4. Ph was also off the scale at less than 6.8. I took a sample to work to check with PH meter and reading was 4.0 which has me scared. The maintenance people have been using chlorine pucks so that is where the acid is coming from. I am going to buy a Taylor 2006 kit as per your recommendation. We have stopped using the pool and have removed the pucks. Is the water salvageable or do I need to start over?pool size is approx 10,000 gallons.


I added approximately 1 1/2 gallon of 48% caustic soda and the PH went too high. Currently it is 9.8. according to the Pool calculator I needed more than 10 gallons. Why did this change so fast?
I bought a poolcheck kit (Unfortunaately a Taylor kit was not available)and my readings now are as follows:
PH 9.8
CAL 400
CALC 150
Alk 125
Cl
Cyanuric Acid >200
Do I have any option other than dump and refill?
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

extremely low ph

Postby chem geek » Tue 30 Sep, 2008 20:21

Your pH may not have really been 4.0 but in any event The Pool Calculator doesn't work very well for large changes outside normal pH and TA ranges. Even my more accurate calculator still requires some accuracy of the TA level and at a pH of 4.0 the TA would be near zero or even negative. So it would be hard to calculate and you'd just add a smaller amount at a time.

In any event, your CYA is too high, assuming it is being measured correctly, so the advice of a partial drain/refill is correct. You could add some acid to get the pH lower -- at least now your pH and TA will be roughly in the range where the calculator will work a little better -- though still add less and remeasure. The main reason to lower the pH at this point is to prevent scaling. Then dilute the water to lower the CYA. Unfortunately, there isn't any other good option other than drain/refill to lower the CYA level.

Is it possible that the pool used Trichlor tablets/pucks for a year or more without adjustment of pH? That could have resulted in the very low pH and high CYA. It's possible that the TA level was very low in which case the 1.5 gallons of caustic soda (which is lye) could raise the pH from around 4 to over 9. Such a situation is tricky to balance right away and I'm sorry you overshot -- I should have warned you about the calculator under such extreme conditions.

To get from your numbers and a pH of 9.8 down to a pH of 7.5 would take 11.6 cups of Muriatic Acid (31.45% Hydrochloric Acid). You could actually just add 7.2 cups of acid to get to a pH of 8.2 since it appears that you don't have much carbonate alkalinity and that most of the TA is from the high CYA level so a pH of 8.2 would give you a decent saturation index. You're going to be doing a drain/refill anyway, but at least you'll be more in the ballpark.

Depending on the type of pool you have, you probably can't do a complete drain/refill and have to do it in multiple steps or you can use the sheet or silage bag method, removing pool water underneath and adding fresh water on top (or in the bags).

Richard

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