Suddenly high pH

[TomTMD]

Tested my water 4 days ago and got

FC: 4.0
pH: 7.4
TA: 80

Added 10 lbs of baking soda (Arm and Hammer) for inground pool at 45,000 gallons. Also added 1 lb of granular diclor. I also use Trichlor tabs in a float.

Retested today and got:

FC:4.0
pH: 8.0
TA:100

It is a bit green and hazy after coming back from vacation last week. Overnight FC test did not change. I have not added and water or other chemicals over those days. Any idea why my pH would change like that? I know that adding sodium bicarb is not supposed to change pH much if at all. Looking for suggestions before I go and buy more dry acid. Thanks.

 

[BoDarville]

Welcome to TFP

Three questions for you:

• 1. What are you using to test pH?

• 2. Do you have any water-aerating features such as fountains or a spill-over waterfall from a spa or other feature into the pool?

• 3. Was your pool surface re-plastered within the last year?

If your answer to question 2 is yes, that will contribute to rising pH although going from 7.4 to 8.0 in four days seems like a lot if this is the only contributing factor.

If # 3 is yes, it can cause pH to rise for up to a year although the effect is most noticeable in the first month or two. Please add info about your pool to your signature so we can quickly rule this in or out as a possibility.

BTW, if your water is "a bit green and hazy", I would consider going through the shock process even though your FC is currently holding steady. If there is some organic matter growing in the pool, the FC consumption can change in the blink of an eye. Before beginning the shock process, you will need to know what your CYA is.

 

[TomTMD]

Thanks for the reply. I use the Taylor FAS kit. Don't remember the number but it is the good one. My CYA is 50. I have no aerator type devices and I have not replastered. I am going to shock today and recheck everything in the AM. My CC is zero and the overnight free chorine was unchanged last I checked so I think it is mostly dead but will see. I know 8.0 isn't terrible and with Diclor shock will probably come down. Just seems like I have had more pH issues this year than most.

 

[jblizzle]

Be careful continuing to use dichlor and trichlor. Your CYA is currently at the top of the recommended range as it drifts up you will need to start to maintain higher FC levels.

Sounds like you have a pretty good handle on how the chemicals behave in your pool. Although what you described was not what we call the shock process, but you do seem to be aware of the tests to stop.

Posted with Tapatalk ... sorry if I sound short ... hate typing on phone

 

[BoDarville]

My CC is zero and the overnight free chorine was unchanged last I checked so I think it is mostly dead but will see.

Given your CC of zero and passing the OCLT, it is possible that whatever is causing the green/hazy effect could very well be dead. Try increasing the run time of your pump/filter and see if this clears it up. Not sure what kind of filter you have but if the increased run time alone does not clear it up and you happen to have a sand filter, you could try adding either DE or cellulose fiber as a filtering aid (see http://www.troublefreepool.com/pool-school/add_de_to_a_sand_filter for process on how to do this). If you choose cellulose fiber (Fiber Clear and ZeoFiber are two brand names), the application process is the same as for DE - just follow the dosing instructions on the package. Giving the pool a good brushing wouldn't hurt either.

As for the pH rise, it seems like the only thing that changed in the four days between your tests is your water going from clear to green/hazy and the addition of baking soda (which as you correctly pointed out has a negligible effect on pH but will increase TA). Unfortunately, it is not clear at this time as to what caused the green haze. If the green haze clears up after increased filtering time and you then clean/backwash the filter, see if the pH stabilizes. If it does, then it is likely that was part of the problem assuming all other factors are held relatively constant.

BTW, continued use of dichlor and trichlor will tend to lower pH but, as jblizzle stated, your CYA is getting up there and dichlor/trichlor will increase that. Just something to keep an eye on.

 

[TomTMD]

Thanks everybody. I have a sand filter and brushed/vacuumed which obviously helped. I have increased the run time from 12 hrs to 16 hrs but will probably just leave the pump on until clear. I suspect I will need to do this a couple of times. I was considering adding the DE as suggested. As per the CYA, I plan to use Power Powder for the shock instead of Diclor. Probably just needs a little attention after a week of vacation.

 

[jblizzle]

Is there s reason you are not using liquid chlorine / bleach for your chlorine needs? It can also be used for the shock process ... even if that aid is not in the name.

If the powder you are new going to use is cal-hypo , that is going to raise the calcium in your pool. What is your current CH level?

Posted with Tapatalk ... sorry if I sound short ... hate typing on phone

 

[TomTMD]

Yes it is Cal-hypo 73%. My calcium is 250 so I have some room on that. Only reason I don't use the liquid is my pool is pretty large (45k) and I would go through several bottles at a time then I have to dispose of the them. I have thought about using it though just to save money if for no other reason.