2nd times a charm.......No Drain Acid Wash

[TXFlyGuy]

Just completed round two of a "no drain acid wash". Used 8 gallons of acid this time and after 2 days all issues with scale and/or plaster dust have been resolved!

The pool now looks better than ever before since being built in 2006. Thanks to everyone for their input on this topic!

 

[JamesW]

Thanks for reporting your results. This could be helpful to others in the future.

 

[TXFlyGuy]

Thanks for reporting your results. This could be helpful to others in the future.

Also used 1 gallon of Scaletec & Beautec in addition to the acid.

This is much better / cheaper / less harmful than a complete drain and acid wash. And the second treatment did not require the intense brushing that was performed during the first application. After 48 hours the issues that had previously drove me insane had abated completely!

 

[HouTex]

Have you tested the water after the treatment? I'd be interested to see if the CH increased dramatically. If calcium buildup was removed during the nodrain acid wash where did it go?

 

[TXFlyGuy]

Have you tested the water after the treatment? I'd be interested to see if the CH increased dramatically. If calcium buildup was removed during the nodrain acid wash where did it go?

The CH came in at 350. It seems that most of it gets filtered out as I had to perform two back washes in the last 48 hours...filter was really clogged up!
Now the water is sparkling clear and everything is back to normal on the chemical side of things. I used 50 lbs of baking soda to re-balance the water chemistry.

 

[HouTex]

I might try this. My CH was 625 two weeks ago before the big rains of last weekend. Maybe it's slightly lower now. I'm concerned that a no drain acid wash would cause my CH to rise even higher forcing me to drain about half, or more, of my pool. With mandatory water conservation in place I risk a $500 fine if I have to refill my pool. I may wait for the end of the drought.

Also, was baking soda all you needed to raise the pH after the no drain acid wash? You didn't need borax or anything else?

 

[TXFlyGuy]

I might try this. My CH was 625 two weeks ago before the big rains of last weekend. Maybe it's slightly lower now. I'm concerned that a no drain acid wash would cause my CH to rise even higher forcing me to drain about half, or more, of my pool. With mandatory water conservation in place I risk a $500 fine if I have to refill my pool. I may wait for the end of the drought.

Also, was baking soda all you needed to raise the pH after the no drain acid wash? You didn't need borax or anything else?

Yes, baking soda! And it works great as it has been used several times now.
My CH levels have never been high, usually around 300 or so. You should not need to drain your pool as the calcium in suspension will be caught in the filter. I did get a lot of dust clouds while brushing during (and after) the acid treatment. And (in my case at least) it all gets caught in the DE filter.

I did not test the water during the acid wash, only after after adding baking soda.

 

[chem geek]

When the pH is very low and the TA is essentially exhausted, then baking soda will raise both the pH and the TA. However, one must be careful not to overshoot the TA level. With pH Up (soda ash; washing soda) one can raise the pH faster with less likelihood of overshooting the TA. If I start with a pH of 7.5, TA of 100, CYA of 30 and add 8 gallons of acid to 30,000 gallons, then I end up with a pH of 3.2 (and TA of -30; carbonate alkalinity near zero), then adding 80 cups (50 pounds) of baking soda raises the pH to 6.4 with the TA at 86 ppm. In reality, less would need to be added since some of the acid would dissolve scale, but the point is that if one continued to add baking soda one could overshoot the TA. Of course, one could aerate to raise the pH but that can take a while. If instead one added 56 cups (32 pounds) of pH Up, the pH would rise to 7.5 with the TA at 88 ppm.

[EDIT] I think in practice that using baking soda when the pH is very low results in more carbon dioxide outgassing so the net effect is very similar to using pH Up in that situation.
2NaHCO₃ --> Na₂CO₃ + CO₂ + H₂O
Baking Soda --> pH Up + Carbon Dioxide + Water
One should still check the TA to make sure they don't overshoot, but can switch to pH Up or 20 Mule Team Borax when getting close to the TA target but still need further to go to raise the pH. [END-EDIT]

 

[TXFlyGuy]

When the pH is very low and the TA is essentially exhausted, then baking soda will raise both the pH and the TA. However, one must be careful not to overshoot the TA level. With pH Up (soda ash; washing soda) one can raise the pH faster with less likelihood of overshooting the TA. If I start with a pH of 7.5, TA of 100, CYA of 30 and add 8 gallons of acid to 30,000 gallons, then I end up with a pH of 3.2 (and TA of -30; carbonate alkalinity near zero), then adding 80 cups (50 pounds) of baking soda raises the pH to 6.4 with the TA at 86 ppm. In reality, less would need to be added since some of the acid would dissolve scale, but the point is that if one continued to add baking soda one could overshoot the TA. Of course, one could aerate to raise the pH but that can take a while. If instead one added 56 cups (32 pounds) of pH Up, the pH would rise to 7.5 with the TA at 88 ppm.

Just did a water test at Leslie's...

FAC- 4
pH - 7.4
TA - 90
CYA - 30
CH - 220
Phosphates - 0

This confirms that most (if not all) of the scale and/or plaster dust has been filtered out. So far, so good....

 

[DBfan187]

pics? before & after

 

[TXFlyGuy]

pics? before & after

The before pic's are on this forum.

I'll post some after shots later!

 

[TXFlyGuy]

Here are the before pic's...

 

[TXFlyGuy]

And.......here are the after photos -

 

[TXFlyGuy]

Notice in the before pic's the milky white area in front of each step, about 4 inches wide and running the entire length of the step. Also, about 2 feet in front of the bottom step is a milky patch about 30 inches wide and runs nearly the width of the pool.

These areas are totally gone in the after photos. There were other trouble spots besides these and they have all been resolved!

 

[Melt In The Sun]

That looks really nice! You don't have a heater, correct?

For anyone else who is reading this and considering it, it is very dangerous to run the water through your heater during this process.

 

[HouTex]

That looks really nice! You don't have a heater, correct?

For anyone else who is reading this and considering it, it is very dangerous to run the water through your heater during this process.

I don't have a bypass for my heater. So, for the 2 days or so that this requires would it be ok to add the acid and then sweep the pool a few times a day to mix the water up? Or should I buy some valves and pvc and install a bypass for the heater? I probably could DIY it.

[edit] And is it likely that my cartridge filter will catch the suspended calcium?

 

[TXFlyGuy]

That looks really nice! You don't have a heater, correct?

For anyone else who is reading this and considering it, it is very dangerous to run the water through your heater during this process.

Yes, I do have a heater. The entire system was shut down for the time the acid treatment was in progress. The system was re-started after adding the baking soda.

 

[dmtranman]

Thanks for posting this. I'm going to give it a try on my pool too. When did you add the Scaletec? Immediately after adding the MA or did you wait for the MA to circulate and pH to go down before adding the Scaletec?

 

[TXFlyGuy]

Thanks for posting this. I'm going to give it a try on my pool too. When did you add the Scaletec? Immediately after adding the MA or did you wait for the MA to circulate and pH to go down before adding the Scaletec?

The Scaletec (1 g.) and the Beautec (1 g.) were added about 6 hours prior (with pumps running) to the acid in order to get it circulated through the pool water.

Prior to adding the MA, the system was put in "service" mode and did not run for 3 days. This is where you get a bit of a workout with your pool brush. Like someone told me, more is better...brushing, that is!

I am still amazed even now every time I look at the pool. It looks very nice today, and prior to the acid wash it was embarrassing to admit that I was the pool builder.
The problem originated from an improper startup. It simply was not brushed, and as a result, a large amount of plaster dust re-deposited on the walls and floor.

 

[Nightstew]

I would note that this is a "pebble" pool, and it can handle these treatments much better than a plaster pool could. Please be careful if you have a plaster pool and are considering this.