Rough plaster upon first Spring opening of pool

[badcpa]

Our plaster pool was completed last fall, and water kept balanced, adding muriatic acid weekly to keep pH down until pool was closed for winter. Upon opening this Spring, the plaster below the winter water level now feels rough (like sandpaper) and appears to have a whiteish haze on the surface of the gray plaster. The plaster that was out of the water during the winter is still smooth (top step and several inches below tile line). We just noticed this last week when it warmed up enough to get into the pool for the first time.

I suspect this is scale due to rising pH over the winter? The pool builder closed the pool in the fall, and this being our first pool, we assumed he would do whatever was necessary with the chemicals prior to closing. When he opened the pool, I noticed that he had to add about 3/4 gallon of muriatic acid, so I know the pH was very high by Springtime. The water was very clear within 24 hours of opening.

My water is balanced now, but what can I do about restoring the smooth surface to the plaster?
My current readings are:

CYA = 40
TA = 100
ph = 7.8 (I keep adding muriatic acid to bring it back to 7.4)
chlorine approx 5 (I have a SWG)
CH = between 200 and 250 (not sure how to read test to know exactly when color changes from red to lavender to blue)
The water is sparkling clear

CSI is currently within the proper range to prevent scaling, but how do I get rid of the roughness that happened over the winter. And then how do I prevent it from happening again next winter?

Thanks.
Brent

 

[JasonLion]

That does indeed sound like calcium scaling. It isn't easy to remove. You could try to do a no drain acid wash, but that can only be tried if you don't have a heater or can bypass the heater, and even then it usually doesn't work. The only reliable solution is a complete drain and manual acid wash.

The underlying cause of the high PH is relatively new plaster. When your plaster is applied in the fall you need to close the pool very late, open very early to avoid problems, and start the winter with a relatively low PH. In any case, there is relatively little chance of this repeating next winter.

You can lower your PH a bit lower each time, say to 7.2. That will give you just a little more time between acid additions.

On the CH test, the lavender/purple color means you have a floating end point. Sometimes you can avoid that by adding five drops of R-0012 right at the start and then doing the rest of the test normally, remember to add the initial drops to the total number when calculating the result.

 

[geekgranny]

I'm very personally aquainted with calcium scale. See two pictures below: Same Blue Plaster Pool Both Pictures. First is 2008, during acid wash, Second is 2004 pre acid wash. All this, of course, was before discovering, summer 2009, THE MOST WONDERFUL TFP.

The scale was so bad on the steps that it took 2 hours, with an 18 volt angle grinder, with concrete disc, to get down to the blue plaster, just on one step. I, slipped and fell, on the decline to deep end and tore a rotator cuff tendon so didn't get the other two done.

I don't want to get anyone's hopes up but......

Last fall, 2009, I did an Ascorbic Acid treatment for stains, copper and iron. It was fall and the water temp was lower than desired, and did slow down the process considerably, I did the AA treatment for about two weeks. I would have gone longer but the dogs were "fit to be tied" having to stay out of the pool for any longer. Treatment successful for iron and a bit for copper. All winter I kept HTH Metal Control (Wally World) in, higher level than "normal maintenance dose" pH at 7.2, water circulating 24/7. Old Aquabot (using fine bags, 5 micron) scrubbing daily, for several hours, all winter into spring, collecting a lot of calcium particulate matter, which is different than our clay and chalk dust. For two months, when old pump and filter were out of system water was kept circulated with two submersible pumps with large Slime bags filtering water 24/7 and Aquabot filtering and moving about 15K to 30K water per day. When water temps began to get higher than mid 40's the scale started releasing in abundance. With my new big DE filter (using cellulose), pump at < 20 gpm, 24/7, and several backwashes it took over two weeks to clear out the calcium that had released from the pool walls and bottom. There was no way it was dead algae as I micro-manage the pool. And the evidence was there before my eyes. It has continued to slowly release even on the steps. With a bad back I really can't do extended amounts of brushing but I do try to hit the whole pool once a week, with a bit every few days, using aluminum brush. (With the 2008 acid wash we didn't get much of the scale on the bottom because we were afraid of doing too much damage to the old plaster, applied in 1996.)

The point is that some scale can be released in certain circumstance but it is a very slow process. It might not work in all scale situations but it certainly is releasing in my pool. My water is kept moving 23/7 and pH never allowed above 7.5; usually between 7.2 and 7.5. Weekly I see a little more blue plaster peeking out from the scale on bottom of pool. I do keep the Metal Control in all the time due to iron carried into my pool via silt. I, also, hope it might have some affect on the copper too.

So, I'm not saying that Jason is wrong, only that there can be rare situations where scale can release, without drastic measures. Acid washing is not fun. I've done it several times, over the past 24 years to my pool. The 2008 acid wash was the only time I had a helper, visiting very good friend. :-D

 

[badcpa]

Thanks for the replies.

Jason--
We did keep the pool open until November 10th, then opened it April 6th (which is about a month later for closing and a month earlier for opening than most pools in our area).

I was hoping that since the scaling hasn't been there too long, it might be easier to remove. Unfortunately, we do have a heater plumbed after the filter and before the SWG that all water passes through, whether the heater is on or off. There is no bypass (without having to run new pipes).

Will waiting until fall to do an acid wash and drain make it more difficult to remove the scale? Is there a sense of urgency to get it off the plaster ASAP, as long as I keep the water balanced and PH lowered during this swimming season?

Good to know that as long as I keep the chemistry in control, this shouldn't repeat or worsen next winter! My problem is nowhere near as bad as geekgranny's, thank goodness!

 

[JasonLion]

The scale shouldn't be any more difficult to remove in the fall/winter than it is now, give or take how much fun it is to work in different weather conditions.

 

[Laker4ever]

"...The plaster that was out of the water during the winter is still smooth...."
I've heard that it is not good to keep plaster dry without water as it will crack.
Why do you think your water dropped? Leak? No rain to compensate ?
Maybe it is wise to add some water such that all plaster is covered even if you don't use the pool, and it is considered "closed"

 

[badcpa]

When they winterize pools in our area, standard procedure is to bring the water level about 6" below the tile line so that the tiles won't crack or pop off if water gets behind them and freezes. The pool is covered with a safety cover until it's openened in the Spring. The 6" gives some leeway for snow melt through the mesh cover. By spring time, the water level was almost up to the tile line.