I have decided to try a no drain acid wash to try and remove some stains i have in a plaster pool. The pool is approx 22,000 gal. Yesterday I added 10 gals of muriatic acid to kill the alkalinity and drop the ph. The question I have is: Assuming I have success with removing the stains, I see that most folks use either baking soda or soda ash to gradually return the ph to normal range. My question is: Can I use Sodium Hydroxide (NaOH) to bring the ph back up? Any drawbacks to this? My thinking here is that the Muriatic Acid (HCl) and the Sodium Hydroxide would react and just form regular salt water. Since I am thinking of converting over to a SWCG generator system this season I was thinking It may save some $$ on the pool salt I will be buying anyway.
Question about raising ph after a no drain acid wash
- Thread starter echo
- Start date
10 gallons of 31.45% acid would lower the TA by about 330 ppm (In 15k gallons), which is very aggressive.
To recover, you would need about 34 lbs of sodium hydroxide.
Sodium hydroxide is very dangerous and probably not worth messing with.
Also, the pH is likely to go super high and potentially cause problems.
I would go with baking soda.
To recover, you would need about 34 lbs of sodium hydroxide.
Sodium hydroxide is very dangerous and probably not worth messing with.
Also, the pH is likely to go super high and potentially cause problems.
I would go with baking soda.
Ahh yes.. I moved to a new home (2yrs ago) with existing gunite pool. I miss the fiberglass pool. It was very easy to take care of and kinder to the bottom of your feet.
**will update the sig
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I am aware of the danger/hazards of using caustic soda. I am comfortable with using it. I was thinking of using the caustic soda (making small additions and mixing it well, then waiting a few hours before reading the ph) to bring the ph back up to 6-6.5 then finish it off with sodium bicarb. Forgot to mention I do the ability to borrow from work a ph meter and buffer solutions.
Seems like a bad idea to me, but I really don’t know if it will cause any significant problems.
It’s your choice.
Let us know what happens.
It’s your choice.
Let us know what happens.
If you have low carbon dioxide, then the addition of sodium hydroxide will not create a lot of HCO3 (bicarbonate), which is what you need to establish the total alkalinity without skyrocketing the pH through the roof.
What was the starting TA?
If we assume a starting TA of 100 ppm.
10 gallons of 31.45% acid in 22,000 gallons would drop the TA by 228 to -128 ppm.
To get back to zero TA and add some carbon dioxide, you can add 41 lbs of baking soda.
After that, you can add 10 lb. of sodium hydroxide to get the TA back to about 65 and the carbon dioxide will buffer the pH rise to keep it from going too high.
As far as the salt goes, the acid added chloride.
The sodium hydroxide and sodium bicarbonate both have sodium and neither have chloride, so it really does not make any difference.
If we assume a starting TA of 100 ppm.
10 gallons of 31.45% acid in 22,000 gallons would drop the TA by 228 to -128 ppm.
To get back to zero TA and add some carbon dioxide, you can add 41 lbs of baking soda.
After that, you can add 10 lb. of sodium hydroxide to get the TA back to about 65 and the carbon dioxide will buffer the pH rise to keep it from going too high.
As far as the salt goes, the acid added chloride.
The sodium hydroxide and sodium bicarbonate both have sodium and neither have chloride, so it really does not make any difference.
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Starting TA was 80.. It has just been a bit more than 24 hrs since adding the acid.. I did some brushing a few hours ago and so far the acidic water does not appear to have much if any affect on the stains . I hope I see some better results in the next couple days
** the muriatic acid I used was 20 Be ( i think that equates to roughly 31.5%)
What do the stains look like?
Sulfamic acid might work, but you would usually want to do a drain and refill after using sulfamic acid.
Note that you don’t want the low pH water going through the heater.
Don’t drain and refill unless you can verify that it can be done safely without popping the pool out of the ground.
Sulfamic acid might work, but you would usually want to do a drain and refill after using sulfamic acid.
Note that you don’t want the low pH water going through the heater.
Don’t drain and refill unless you can verify that it can be done safely without popping the pool out of the ground.
The stains look like amber colored splotches ( kind of similar to the color of iced tea) the stains are actually hard to see in bright sunlight but easy to see on an overcast day. I was afraid to drain the pool because of the possibility of it popping out of the ground. This is why I am trying this no drain acid wash. A few days ago when the pool was opened the water temp was 51 deg f. I have the pump shut off and the valves closed to prevent the acidic water from reacting with the heater/pump.. We had two full days with ~80 deg temps water temp is now in the low 60's . Maybe the cool water will slow the acid reaction on the stains
Can you show the stains?
Maybe it's iron?
Try dropping a vitamin C tablet on the stain.
Maybe it's iron?
Try dropping a vitamin C tablet on the stain.