Calcium Hardness

[JFS]

installed my 17K gal plaster/gunnite pool in So Cal 25yrs ago. I have always done my own maintanance and was from the old school in that I checked my total chlorine and PH twice a week and total alkalinity every 3 weeks. I guess I have been lucky since I have never had a serious algae issue and have never experienced cloudy water. I also made a point of draining about 75% of my water every 3 yrs... 6 mo ago I began visiting this forum regularly and have become aware of the complexity of water chemistry, I have also become competely paranoid.

A month ago I drained 75% of pool and added phosphate remover, my phosphates were 2500. Today I took water sample to store:

FC 3

PH 7.6

TA 100

CYA 100

CH 620

Phos 300

I use dichlor tabs and keep pool at 85(solar).I put a bag of cal hypo shock in 3 weeks ago where in the past I have always used dichlor shock from Home Depot. My pool store was alarmed at high CH and told me to bring in sample of tap water. I was under impression that draining pool was method of resolving high CH levels, which I have already done. I would appreciate comments on how serious this problem is and how I might go about resolving it.

I would also appeciate recco on a test kit, where to buy.

Many Thanks-Joe

[waterbear]

The test kit you want is a Taylor K-2006

http://www.taylortechnologies.com/products...&KitID=2230

(NOT the K-2005). You can get it from several online sources or from Taylor Technolgies. You can get the same kit on the Leslie's website as the Chlorine FAS-DPD Service Test Kit http://www.lesliespool.com/browse/Home/Wat...:400000/I/81329

It is the same kit but rebranded by Leslie's.

CH is lowered by adding water with lower CH than the pool. If your fill water is very hard that won't work! CH of 620, while high, is managable if you lower your TA to the low end (around 90 ppm if you are using trichlor tabs, which will cause your CYA to rise again, btw!) and keep tabs on your pH and do not let it rise above 7.8 (which should not be a problem with trichlor. If anything you need to monitor the TA and pH to make sure they don't drop and crash!)

[katthepoolchick]

Well I have to say that is quite a high CH reading. Normally if a customer has a super high reading I would have them do a stain and scale to prevent calcium buildup on you equipment. Keep an eye on your pump and seals to make sure no leaking has started. Your stabilizer reading is a little high, the only way to lower that though is to dilute the water.If you drain the pool again or dilute it, do not add any stabilizer or calcium to the pool. Your Tabs/Stix will add the stabilizer as well as any dichlor shock. You want your CYA level to be around 60 ppm. Since you are using cal hypo you are pushing your calcium level up more and more. As for the phosphates, if they are staying high on a regular basis, see if you can find a pool store that carries Natural Chemistry Phosfree and Pool Perfect + phosfree. It takes the place of using an algaecide. Great product. Also SeaKlear has a great phosfree product.

[quantumchromodynamics]

1) Get the K-2006 test kit from Taylor.

2) Stop worrying about phosphates.

3) Stop using chlorine sources that contain calcium or cyanuric acid.

4) Use liquid chlorine or bleach for chlorination.

5) Post a full set of chemical readings for your tap water.

6) Dilute your pool test water 50% with tap water before doing a cyanuric acid test and then double the result to get a more accurate cyanuric acid reading.

7) Dilute your pool to get your cyanuric acid below 70 ppm.

[PaulR]

1) Get the K-2006 test kit from Taylor.

Or the TF-100 from tftestkits.net, which has more generous amounts of the same reagents as the K-2006, and outstanding customer service.

--paulr

[billp]

I guess I have been lucky since I have never had a serious algae issue and have never experienced cloudy water. ...I have also become competely paranoid.

Well sounds like you did pretty well for 25 years so maybe you should not take everything here too seriously!

I use dichlor tabs...

you mean trichlor tabs

I put a bag of cal hypo shock...

If you have high calcium this is not the shock of choice. If you have high CYA then Dichlor is not the shock of choice. Pretty much leaves liquid chlorine as the shock of choice.

My pool store was alarmed at high CH...

You are in what I would call the mid-range manageable CH level. 1,000 ppm CH is alarming.

Although some here poopoo phosphate removers they are another tool in our toolbox and sometimes are a very handy tool. Definitely NOT a silver bullet tho.

If high CH is a persistent problem another solution is to soften your make-up water so you can control the CH level between 200 & 300 ppm. Draining, or 75% draining every three years is probably the best thing you have been doing. Only problem now are the water restrictions you probably have in your area. If you don't have them yet and it is near the 3 yr mark, do the drain and refill soon! before they impose them. Water is the cheapest (fixit) thing you will ever add to your pool.

[Ari]

When my pool was new, the CH hovered around 260-270. I chlorinate with liquid chlorine, but I do occasionally put in a bag of cal hypo, I like the results of adding the cal hypo once every month or so, but after a year or so, I have seen my CH creeping up, partly I'm sure because of the cal hypo once a month, also since the pool is still fairly new.

My question is this, I'd like to be able to add a bag of cal hypo once a month to my 15,000 gallon gunite/plaster pool, my CH is currently around 290-300, at what level should I consider my CH so high I must stop the monthly bag of cal hypo? Is 300 already so high I should stop immediately, or is 300 low enough where I could go up another 100 to 400 and not have scale or other issues?

If it matters I target a fairly low TA of around 60 as it seems to be a sweet spot for keeping my ph stable. My understanding is if my TA is low, I can have a higher CH and have the saturation index be pretty good.

So, at what CH would I be in danger of developing any issues? Am I already there at 300, or do I have some more headroom, if so how much?

Thanks.

[chem geek]

Put your pool water chemistry numbers into The Pool Calculator to calculate the saturation index. If it's up to +0.3, you're still probably OK though if you had a saltwater chlorine generator (SWG) pool then you'd possibly get more scaling in your SWG cell. You could also get some scaling in a gas heat exchanger if you use it a lot. Other than that, you probably won't see scaling in the pool itself until the saturation index got to +0.7 or higher unless you have some spillover of similar water feature.

You can enter in a Calcium Hardness (CH) value into the calculator to see how high you could go before the saturation index starts to become a potential problem for scaling.

[PaulR]

I like the results of adding the cal hypo once every month or so

What are the results of adding cal hypo, that you like? The Pool Calculator suggests that 1lb cal-hypo at 73% in 15,000 gallons adds around 6ppm FC as well as a little calcium. Would adding 6ppm FC with bleach/liquid chlorine have the same likable result? (And it wouldn't add any calcium.)

--paulr

[Ari]

Well this sounds silly, but I feel like the water seems just a tiny bit fresher and cleaner after using the cal hypo as opposed to the liquid I normally use, which like most I get refilled at the pool store.

Also, I had gotten a good deal on a case of leslie's power powder plus and would like to not waste it.

So for these reasons I'd like to add a bag once a month as long as I can sort of get away with the added calcium, as I said, I'm at 300 now, how high can I go before I hit problems?

I tried to use the pool calc. But it didn't seem to work, because it appeared to be saying I could, actually SHOULD let my CH go VERY high, like 600, to get close to 0, at 600 ppm it had my index at +.02

My numbers were:

ph on average is 7.6

ta is 50

temp is 87

FC around 6

CYA 50

it seemed to say I could go higher than 600 ppm CH and still be near 0.

Am I doing it wrong?

[chem geek]

You are doing the calculations correctly. The reason that your Calcium Hardness (CH) can go so high is that your Total Alkalinity (TA) is very low, especially since your Cyanuric Acid (CYA) isn't low (about 1/3rd of CYA counts towards TA). So your pH buffering is rather low. So long as you use hypochlorite sources of chlorine, this isn't horrible -- a higher TA mostly protects from pH "crashing" low from Trichlor which is very acidic -- however, your pH may swing a lot if you add a lot of chlorine at once. To minimize this effect, you could consider using 50 ppm Borates which will provide additional pH buffering but won't contribute to scaling (i.e. it won't increase the saturation index).

So yes, you could use Cal-Hypo for some time since you've got a lot of room for increase so long as you keep your TA where it is. Since for every 10 ppm FC using Cal-Hypo it increases CH by 7 ppm, even if you used Cal-Hypo as your sole source of chlorine every day at 2 ppm FC per day usage, it would only increase the CH by 42 ppm per month or around 250 ppm in 6 months. Since you plan on only using it once a month, you won't have any problem at all -- you could even use it weekly. Keep in mind also that your TA and CH may rise from evaporation and refill since your fill water has TA and CH in it.

[Gary45]

Thank you for this useful topic, I learned a lot

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[chem geek]

Not sure if I have just done something wrong here, tested my Calcium today and found that it had dropped to 380ppm, to bring it back up to its normal 410-420 I have added some Calcium Buffer only to find that most of my soft corals have closed up and dont look very happy, is this normal or have I done something wrong?

Mark

Mark,

Are you talking about an aquarium or a pool? Calcium levels of 410-420 would be on the high side unless your Total Alkalinity (TA) or pH were low. This is a pool and spa forum, not a forum for aquariums.

When you say you added calcium buffer, what are the ingredients? To increase calcium, you add calcium chloride, but that would not be a "calcium buffer" and I'm not even sure what that means exactly. There are carbonate buffers, phosphate buffers, borate buffers that all help stabilize pH.

Richard