Need help to better balance for CSI...questions

[Sandra B]

Hi all. Hope you experts can help me on a CSI question, I've read, and thought, and worried over this, then read some more, but I need some hand-holding.

My pool is now around 8 yrs old; I've had it for the last 4. Over the last year I have have a few strange things occur, which I am now attributing to early-stage plaster delamination: small "volcano" calcium deposits on the pool floor and steps; calcium drips on the walls; some "cracks" or crazing on the floor, and finally darkening areas, almost like color streaks, on some pool walls. This was accompanied by a meteoric rise in my CH. I keep a log on my pool testing (TFT-100) and the CH has gone like this:

7/23/11: 170 (first test with kit)
7/28/11: 290 (I raised it)
4/16/12: 270
5/21/13: 300
1/13/14: 300
6/19/14: 320
7/21/14: 400
8/05/14: 460 (starting to panic and really read up here)
8/23/14: 550
9/02/14: 630
9/28/14: 760 (drained about 1 foot of water & replaced, maybe 10% replacement?)
10/6/14: 570 (result of water replacement)
11/12/14: 650
12/27/14: 700
1/17/15: 650 (may be result of 8 inches of rain in January)

My tap water CH is 30.

As of yesterday, stats are:

temp: 51 degrees
Salinity: 3000
FC: 7.0
TC: 7.0
pH: 7.4
TA: 50
CYA: 45-50 (sock hanging to raise to 70)
Borates: 50ish

I am trying to balance my CSI to help with the calcium problem, but I struggle with this. With the current readings, my CSI is -.65. From Pool Math, in order to keep CSI close to zero, I need to left my pH stay higher, around 7.8 or so (adds .3), and raise my TA to around 80 (adds .3). Adding the CYA has a small opposing effect (minus .1). This would get me close to zero. My TA generally drifts between 50 and 60 so I normally don't mess with it. My pH rises fairly regularly so I'm always pushing it down with MA. The high CSI confused me a bit, since I've been keeping an eye on it all summer and it was ok, but playing with pool math made me realize that lowering ONLY the water temp, from 90 (my summer water) to 50 (my winter water) has a huge impact.

I plan to add 128 oz of baking soda, which will have the effect of increasing the TA and slighting increasing the pH, so all is good with that. Before I go do that (half at a time), am I doing the right thing? Will the 80 TA pose any problems?

Do you believe that my out of control CH is due to delamination, given the other symptoms? I suppose the only cure is to some day replaster, but I'd like to try to manage it for a few more years if that seems possible. It seems too young to replaster! I've thought of calling the pool builders over to take a look (they're a big company in town and have done a couple equipment maintenance items for me over the last years) but don't know what that would help.

Photos can be added if they're helpful. The pool is sparkly and beautiful this sunny day . Just don't look too close...

Thanks!
Sandra

 

[duraleigh]

Are you using Calcium Hypochlorite to chlorinate?

 

[Divin Dave]

Hi Sandra,
I dont think Im qualified enough to definitively speak to your CSI. So hopefully someone else will jump in too.

I do know that sometimes its a bit difficult to keep in check, especially since the water temp plays such a huge role.

Calcium scaling is typically the result of the high CH combined with PH above 7.5. I think TA plays a role in the equation too.
Keeping your PH in the 7.2 to 7.4 range will help out with that.

Question. Would draining 50% and refillling, to get the CH down be an option for you? I dont know about Shreveport, but our water over here in Longview is pretty cheap.

If so, I would recommend doing that before anything else. Raising your TA will probably also mean your PH will rise a bit quicker too, whioch means you have to keep a sharper eye on it so it doesnt get about 7.5 again. So I'm not so sure that raising the TA considerably would be the best choise until you understand what is going on a bit better.

As for the scaling, have you considrered an acid wash ?

 

[Sandra B]

Thanks for the help. My only chlorination is SWG. I installed a new cell 2 summers ago and it more than keeps up. Before that occasionally added Clorox. Nothing else added in 4 years except MA, calcium hardener in 2011, CYA, and borax in June 2013. No pool store additives in my ownership, 4 years.

Dave, that's what so confusing to me. If I keep my TA and pH low, then my calcium saturation index is too high (at -.65), so it's in scaling territory. I do like to keep them on the low side, thinking that would help the scaling, but with the water cold, the low numbers seem to hurt rather than help. That's where I'm thinking that in the winter I should keep the TA and pH higher, and in the summer keep them back down. Ugh. The ONLY difference is temperature.

You're right about the water cost. I'm in a HOA where water is paid by the monthly HOA fee, with an annual add-on of $150 for pools. So I could drain the whole thing with zero incremental cost. I'm a bit worried on how much to drain, given than I'm about 1/2 mile from the Red River and a river bayou arm comes within 200 yards. I expect my water table is fairly high, so I'm thinking maybe 2 feet at a time, doing it four or five times before May (shallow end is 3.5, deep end is 6.5).

I haven't considered an acid wash yet because I'm not sure that it's a scale problem or a delamination problem...

Thanks for your help! Much appreciated.

Sandra

 

[JasonLion]

I strongly suspect that your fill water CH is not the same as your tap water CH. This commonly happens when you have a water softener, but pool gets filled from a hose big that taps off before the water softener. If you haven't already, make sure you test the water you actually use to fill the pool for CH. If I am wrong about this, you need to figure out where that CH is coming from fairly quickly. Keeping the PH too low can etch calcium out of the plaster and into the water, but CSI would need to be even more negative than it is now for that to be at all likely.

You are not trying to get CSI to zero! You are trying to keep it between -0.6 and +0.6 (or +0.3 if you have a SWG), something which is much simpler.

The obvious, and fairly simple way to get CSI in balance is to increase your PH. You don't want your PH that low regardless. The lower you keep PH, the faster the PH will go up. Also, when the water is cold you should be raising the PH slightly anyway.

 

[chem geek]

With the 50 ppm Borates and the rather low saturation index of -0.65 you should not be getting calcium carbonate scaling in your salt cell unless for some reason it doesn't regularly reverse its polarity. As the temperature of the water gets colder, you want your pH to rise on its own and that will naturally keep the CSI about the same.

I have had something very similar to what you have experienced happen in my pool starting after around 7 years of age (I've owned it the entire time) where I'd get calcium nodules, my pH would rise much faster than before, and my CH would either not drop as usual over the winter in spite of rain dilution or would rise some during the summer (not as much as you are seeing, however). You can read more about calcium nodules and other plaster problems in the threads Calcium Nodules in Pools and Diagnosing Pool Plater Problems). Some of the volcanoes would crack and plaster be removed and I could see clearly that it was delaminating because of a poor plaster job that created voids. This is not a water chemistry problem but rather a problem of poor workmanship not carefully applying the plaster evenly to prevent voids and possibly not using proper materials to encourage proper bonding between the plaster and the gunite. In my pool, most of the problems were in the slope between the shallow and deep ends, though the deep end also has some issues (there are some drips on the walls in the deep end as well).

In my situation, things settled down after a few years and the pH and CH rise slowed down considerably. It is possible that your keeping a more negative saturation index is encouraging small pitting that accelerates breaking through to the void with calcium hydroxide that then creates a calcium nodule or drips on the wall of calcium carbonate, but again fundamentally the problem is with having the voids and improper bonding of the plaster to the gunite in the first place. However, my CSI was not as negative as yours yet similar problems occurred.

Unfortunately, my pool builder retired, but if you contact yours and get an opinion on what is going on then I'd be interested in you posting what the PB says. My pool is now 11 years old and I'll probably need to replaster before 15 years and this time I'll know more to make sure the subs plaster carefully, the PB uses a bicarbonate startup, that they don't use too much calcium chloride in the mix, etc. I'm willing to pay more for them to take their time and do it right, if necessary. Unfortunately, a replaster never quite bonds as well to the gunite as an initial plaster job, but they should at least be able to avoid creating voids.

 

[Sandra B]

Thanks Jason & Chem Geek. Jason, I don't have a home water softener, but I checked my hose water just in case (I do have to fill for evaporation here in the summer one a week or so, plus when I backwash.) The hose is basically the same as the tap--it came in at 40 CH.

I've read every single thread on calcium nodules and drips, etc. I thought it was ME until then, but once I read those I became convinced it was the pool. Chem Geek, when I was sanding the calcium "drips" last summer, to smooth them to the surface, I did see that one of them had resulted in part of the wall--a very small part, less than 1"x1/2", was delaminated. Since then I don't sand any more, but I never got any new drips, just little floor volcanoes about 1/4 inch round, but probably 50 of them. Ugh, this is such a pain, because I'm such a perfectionist! I'm going to do some drains/refills over the spring and see what happens if I start the summer closer to 300 again. It's just crazy how fast the CH rises! I'll also let my pH hang a little higher during the cold water season. I fear a replaster is in the future, but will try to keep managing it until then.

Thank you all! Will report back.

Sandra