I just completed a no drain acid wash on a marcite pool (16,000 gallon) using 12 gallons of muiratic acid over the past two days. It removed all the copper stains after brushing with a steel bristle brush and the pool surface looks as good as when I had it remarcited. The water is cloudy I assume from the brushing and has a a number of scum patches on the surface. PH is and AK is not even registering. As such my question is how to I now go about getting the water chemistry right? I did add about 2 lbs of PH up to neutralize the acid as well as did a partial drain and refill (running the pump on discharge while adding fresh water for a couple of hours) but the PH has yet to register.
no drain acid wash
- Thread starter davidtfull
- Start date
If you have a Taylor K-2005 or K-2006 test kit, or even one of the smaller ones, there's a base demand test that can help you get things figured out. You just count drops until the pH looks right and use the chart they include with the directions to figure it out the amount to add. Video
I just have a basic test kit. It checks Chlorine residual, ph level, acid demand, and total alkalinity. It does not have a base demand test.
You can buy the reagent separately if you want.
Otherwise, I'd say start with raising TA to about 50 -- that's like 14 lbs of baking soda. Let it mix, see if pH shifted at all, and then start adding washing soda according to poolmath. You might be below the minimum on the scale, so just enter the minimum value and target 7.4 and add what it says. Repeat as needed until it comes into range.
I added 12lbs of Arm and Hammer baking soda and I am running the filter continuously...checked the TA after 2 1/2 hours and it is now reading 20ppm, whereas before I could not even get a reading. The PH is still not registering, I am getting a yellow color similar to what you see with a chlorine test when I test the PH. How long should I wait before taking another TA reading? I understand that I want to get the TA within range before trying to raise the PH.
If you brushed up any powder that settled, I'd say you already waited long enough. Some of that baking soda must have done the outgassing thing and nudged the pH up a little. Hit it again.
The powder hasn't really settled...in fact it appears that a small (dirty) milky plume is floating on the surface instead. The plume disappears when I agitate the water only to return a while later. At the filter where the water enters the pump (at the basket) that too has a white froth to it. Kinda like sudsy water. When you say hit it again do you mean add another 12lbs of baking soda? Or should I just run the filter overnight and check it in the morning and go from there?
After adding a total of 24 pounds of Arm and Hammer baking soda I was able to get the total alkalinity up to 120 ppm. Even at that high of total alkalinity for a couple of days the PH still did not register. Added 6 lbs of sodium carbonate and was able to get the ph up to 7.2 Then I added chlorine to get that up to 2.0 Added Ultimate Metal Control to handle the copper that caused the staining to begin with. I have also been running the filter continuously and cleaning the filter cartridge daily.
16,000 gallon marcite pool.
Current Readings:
Free chlorine 2.0
PH 7.2
Total Alkalinity 120
Now the pool light shows a ton of very tiny bubbles in the water. The return jets are not showing any bubbles at all. Checked the suction side of the pump and the strainer basket at the pump and no air leaks detected. There are no bubbles in the basket either. The water is clear enough to see the main drain and the outline of the pool itself but no where near as clear as I would like it to be.
16,000 gallon marcite pool.
Current Readings:
Free chlorine 2.0
PH 7.2
Total Alkalinity 120
Now the pool light shows a ton of very tiny bubbles in the water. The return jets are not showing any bubbles at all. Checked the suction side of the pump and the strainer basket at the pump and no air leaks detected. There are no bubbles in the basket either. The water is clear enough to see the main drain and the outline of the pool itself but no where near as clear as I would like it to be.
Most likely that's bits of the pool finish. What you did is not so different than starting new plaster. Give the filter time to clear it.
Wow David, so you went big. 12 gallons of Muriatic acid in a 16,000 gallon pool. I put 6 gallons in a 22,000 pool and it lowered my PH to 3.9 and my ALK to 0.
Can anyone figure out what his PH probably dropped to?
maybe I need to go bigger.
Can anyone figure out what his PH probably dropped to?
maybe I need to go bigger.
I wouldn't, it will damage your plaster and shorten its life. And for future readers, remove the light and do not run the pump during an acid bath. PH below 7.0 is highly corrosive to all metals. It will dissolve the copper in a heat exchanger.
More here about why more acid is not better, The Zero Alkalinity Acid Treatment
More here about why more acid is not better, The Zero Alkalinity Acid Treatment
In the zero ALK acid treatment it says "Assuming a total alkalinity of 100 ppm, it requires 4 gallons of muriatic acid (31.45% strength) per 20,000 gallons of pool water to reduce to zero alkalinity, and to a pH of 4.5."
The acid bath only works because it is corrosive. The entire process is you are trying to let the acid eat away a thin layer of you plaster in a controlled environment. This by default damages and shortens the life of your plaster.
I got to think the OP lowered his PH to about 2. My PH has been around 4 for 2 days now and the results are very slow. I will ride it out for another day and decide what to do.
The acid bath only works because it is corrosive. The entire process is you are trying to let the acid eat away a thin layer of you plaster in a controlled environment. This by default damages and shortens the life of your plaster.
I got to think the OP lowered his PH to about 2. My PH has been around 4 for 2 days now and the results are very slow. I will ride it out for another day and decide what to do.
The large amount of acid I ended up using was the result of removing severe copper stains using a 1 1/2 pvc pipe and spot treating the stains. The stains were so bad I was seriously thinking of remarciting the pool even though I had that done eight years ago. The stains resulted from my son adding way too much algicide that contained copper. It took about a week, with constant brushing and vacuuming through the waste and adding replacement water, to get the pool to look like new. I realize that doing this shortens the life of the finish but compared to the cost of remarciting the pool I felt it was worth the gamble. But this is not something to try if there is ANY other possible solution. Took a bit of work to get the water balanced as well. But all the numbers are now within specs (holding steady as well) and the pool looks great. I think I resolve the tiny air bubbles as well. Even though there was no air bubbles in the strainer, and the return jets were clear, I put a bead of silicone around all the pvc fittings on the suction side and bubbles dropped dramatically. Again I repeat this type of acid wash IS NOT recommended as a first line treatment (even second or third) but rather one of last resort when all else has failed. I will post a picture tomorrow of the final results. I appreciate all the help from the members here. Thank you.
