pH took a nosedive after too much muriatic acid

[weiyin]

Hi,

I think I made a mistake but am not sure how bad. Over the past two weeks, my pH has been consistently high around 8.0, and I tried adding a cup of muriatic acid at a time. pH would go down to 7.8, then back up to 8.0 after 2-3 days.

Today, I decided to go big and poured about 2/3 gallon of 20 Baume muriatic acid. pH from my K-2006 kit now bottoms out at 7.0. Not sure if it's actually lower due to being off the scale. I tried the base demand test and one drop would change the color to 7.2, another drop would be 7.4. Total Alkalinity is at 60.

Should I do something to fix the low pH, or just wait for it to creep back up? I am currently running the waterfall to increase aeration.

 

[weiyin]

Note: CSI is currently at -0.87.

 

[mknauss]

Check TA in the morning. If below 50, add enough baking soda to raise TA by 20 ppm.

 

[pjt]

Today, I decided to go big

What were you trying to accomplish?

Total Alkalinity is at 60.

Are you continuing to add drops until there's no additional color change? With a true TA of 60, the pH will quickly rise on its own back into the 7s. Let us know what your pH and TA are tomorrow.

Note: CSI is currently at -0.87

Momentary excursions are not a problem.

 

[weiyin]

Thanks for the advice. I just tested pH and it has risen to 7.2.

When testing Alkalinity, I would usually stop when the green turns to red (6 drops). But I tried another drop and it turned deeper red. The 8th drop resulted in no change. So I guess my Alkalinity is 70, not 60?

As for what I was trying to do, I was trying to get my pH to a more "ideal" level of 7.6. Maybe I'm overthinking things and doing too much.

 

[mknauss]

Your TA would be 70 with your description.
No need to drive 'ideal'. pH in the 7's, TA above 50. All is good.

 

[pjt]

The 8th drop resulted in no change. So I guess my Alkalinity is 70, not 60?

Yes.

I was trying to get my pH to a more "ideal" level of 7.6

When your pH rises into the low 8s, add enough MA to get your pH into the high 7s. You don't want to lower your TA to 40 or below. 50 and above is perfectly fine. You will likely achieve the most stable pH with TA 50-70 and pH in the high 7s.

Do you have a SpeedStir?

What's the TA and CH of your fill water?

Are you using PoolMath?

Are you tracking CSI?

 

[weiyin]

I use the Taylor K-2006 kit but no Speedstir. Kind of wish I had one now, especially for the TA and CH tests.

My fill water is connected through the house's water softener. It has 0 CH and 160 TA.

Yes, I am using PoolMath and tracking CSI.

I just did a full battery of tests yesterday evening:
FC 8.0
CC 0
pH 7.7
TA 70
CH 240
Salt 3800
CSI -0.18

I am shocked at how quickly the pH bounced back up.

Btw, @pjt I just noticed your location. We are practically neighbors!

 

[pjt]

no Speedstir

Order one today. Not kidding.

My fill water is connected through the house's water softener. It has 0 CH and 160 TA.

Consider filling from a normal hose (non-softened water) to add some CH to your pool. Test your non-softened fill supply for CH and TA.

I just did a full battery of tests yesterday evening:

Your CH is a little low and you didn't post your CYA. CH can be gradually increased by topping up with "hard" water.

I am using PoolMath

Enable sharing your PoolMath logs.

tracking CSI

Maintaining a CSI between zero and -0.3 is ideal for your SWCG. You'll likely never need to clean it.

 

[weiyin]

Poolmath log share enabled. I started taking over my pool on Jul 30th. The test from May was reported by my pool guy.

What do you think about staying with softened water and adding calcium chloride?

I tested CYA after adding some two weeks ago, it was between 30 and 40, so I put 35.

 

[pjt]

What do you think about staying with softened water and adding calcium chloride?

You could, but if you need to add water anyways, why not add water that has some calcium in it?

I tested CYA after adding some two weeks ago, it was between 30 and 40, so I put 35.

Round up to the next 10, so consider your CYA 40. That's low for our climate in the summer (I'm at 90). CYA slowly decreases with hot, sunny weather (~10/month), so keep an eye on it.

 

[weiyin]

I guess my thinking is that if my fill water has calcium, then CH will constantly go up as water evaporates and is replace by fill water. We don't swim in the pool much so I don't know how much splashout there will be. And adding calcium chloride doesn't seem too expensive.

Agreed, my CYA is low. When I took over a month ago it was almost undetectable. I added 4 pounds of Clorox CYA to raise to the current level. I want to monitor the pool at the current CYA level, in case I need to SLAM. Planning to add another 4 pounds next weekend.

 

[pjt]

I guess my thinking is that if my fill water has calcium, then CH will constantly go up as water evaporates and is replace by fill water.

Just fill with a garden hose until your CH is raised a bit. When your CH is where you want it, let your softened water keep your pool topped up.

I want to monitor the pool at the current CYA level, in case I need to SLAM.

Very unlikely you have contaminants given FC 8, CC 0 and CYA 40. You can perform an OCLT to confirm.

 

[proavia]

For the CH test - use a 10ml water sample. Each drop is 25ppm - more than good enough resolution and saves on reagents.

For both the TA and CH tests - continue adding drops until the last drop doesn't change/intensify the color, and then subtract the last drop that didn't change the color.
Be sure to hold the reagent bottles perfectly vertical, allow the drops to fully form on the tip and let the drops fall from their own weight. Do not force the drops off. Dispense at about 1 drop per second.

Get a speed stir or similar - it makes testing so much more accurate and easy.

Using a non-soft water hose bib will help bump up your CH a bit at zero $$$ cost to you. After the CH is around 300ppm (+/-25) switch back to your soft water source.