Calcium hardness causing problems?

[nicole712]

I have been reading all the great posts here and I know SOMEone will be able to help me!! My 3 1/2 year old pool is having 'issues' and I am worried it may have something to do with the calcium hardness. I have never tested it before this year because until now I only had the chlorine/pH test kit.

This Spring I have a really bad white 'ring around the pool' and the plaster looks stained pretty much throughout the pool - it looks splotchy and brownish. It does not sweep off. Is this what you refer to as 'scaling'?

Here are my test results:
CH - anywhere between 460-500 (tested my tap water too, it's only 20)
FC - 2
TC - 2
pH - 7.4 (just added acid because pH had gotten up to 8.2 - my pH always seems to creep up, so I have to regularly add acid)
TA - 110
CYA - 45 (just added some this week because it was almost non existent)

I have a salt water generator and unfortunately was not good about testing the pool this winter (I am in CA). I had black algae in a few spots last month (Chlorine generator stopped generating and I didn't realize it... it was low on salt, but that is taken care of now).

So I guess my questions are...
Is my calcium harndness too high? (I've seen conflicting information)
Where does the calcium come from??
Is there anything I can do about the ring around the pool and the 'stained' plaster?

Thanks so much for your help!
Nicole

[mas985]

Nicole,

Have you tested your fill water yet? In my area, I have pretty high CH in my fill water which makes my pool fairly high (~350 ppm). If your fill water has lower CH, you can partially drain the pool and refill to lower it. If your fill water has just as high CH, then about all you can do is work around it.

With the numbers where they are, your PH needs to be around 7.3 and no higher than 7.8 to prevent scaling. If you cannot lower your CH, I suggest lowering alkalinity down closer to 80. This will bring your balanced PH up to 7.4 but try to keep the PH below 7.8 and that should help a bit with your scaling. Also, SWGs tend to raise PH so when you lower the PH, try to get it down to 7.2 so you have some room for it to rise during the week. This will help keep your alkalinity from rising if it is too high in your fill water.

[CarlD]

Nicole:
Is your pool vinyl or concrete/plaster/tiled?
What is the volume of it?
Have you tried ascorbic acid to clean the walls? I gather it's pretty good on stuff like that.

[salinda]

I am also in CA with SWG and Calcium is 520. I don't have scaling. I keep my ph in check with a good dose of muriatic acid once per week and my alk is at about 90. We got a lot of rain this winter so the salt got diluted. I was hoping the Calcium would too, but it is the same as last fall. I am thinking that a little bleach in the winter would do a lot of good...actually thinking of disconnecting the swg this coming winter since I let my water temp drop and the salt gets diluted in rainy season anyway.

Have you tried soaking your cell with muriatic acid solution?

[nicole712]

Thanks for all the replies - here are the answers to your questions and more of my own questions:

I have an inground plaster pool, about 18,000 gallons

My fill water has a calcium level of only 20 so I have no idea where all this calcium came from!

I have not really tried anything yet for the stains, except for pumice stone (lots of elbow grease required!!) - do you mean for me to try ascorbic acid on the tiles or on the plaster stains?

I know I can partially drain and refill to lower the CH, but do I NEED to do that? (I'm a little worried about getting everything back in balance with new fill water.) Is the CH causing the problems or can I just leave it be and concentrate on the alkalinity? I will do the partial drain if it will help though...

And what about the dirty looking, stained plaster - is that something I need to deal with more aggressively? Is it something I have to treat specifically or will changing the water chemistry help? Is it a sign that something is terribly wrong?

I will try to lower the pH and TA down even more to see if that helps. My TA was back up to 130 this morning, but pH was still 7.4

Oh, and Salinda, yes, I regularly have to soak my cell with muriatic acid - the deposits on it get so bad!

Thank you!!!
Nicole

[PatL34]

Keep working with the Muriatic Acid and aeration to lower pH and TA. The ring around the pool should gradually disappear.

The "brownish" stains could be a form of algae, and steady SWG operation might help to reduce it adding more bleach to save the cell life.

Hope this helps.

Pat

[KurtV]

The scale on the tile will also come off very easily with a strong muriatic acid solution and a green pad. I use a squeeze water bottle to apply the acid, wait a few seconds for it to act on the scale, and then scrub it off with a green pad. Repeat as necessary. You need to wear good eye protection and latex gloves, be mindful of the wind direction and careful of the fumes. You also need to keep it off concrete, stone, and metals.

Always remember to add acid to water and not vice versa.

[nicole712]

Thank you, Pat and Kurt for the replies. I just added some extra chlorine bleach, and some more acid to lower pH. I will try the acid to clean the tile ring.

Nicole