Fiberglass Pool Scaling And Green

[chapinSC]

We've had five different fiberglass pools over the past 26 years and have never had a problem like this. Our chemicals were perfect during the past very hot summer in SC, however as the weather cooled in September, the pool turned a light green color. I cleaned the cartridge filter and it was coated with a thick, slimy, grainy white substance. About 2 weeks later, I discovered that same white slime-like substance covering the entire pool surface (under the water line). When you rub your hand over the surface, you get a chalky, slimy substance that is quite thick and doesn't dissolve off your hand in the water. You have to rub hard to get it off your hand.

I went to the local pool store for water analysis. Here's what they gave me:

FC +5

TC +5

PH 7.4

TA 110

AA 80

CYA +100

CH 70

salt 4,000

phos 2,500

They wanted to sell me a bunch of products to lower phosphates and deal with the green color, which they said was absolutely algae, and told me to start by draining half my pool to bring CYA down to 50. But my concern was with the slimy white substance coming off my pool, which they said they had never heard of. Because I've had bad experiences with folks who supposedly were trained in pool chemistry, I told them I wanted to research the slime problem before adding any chemicals. In checking various sites, it seems my slime problem is due to low CH, but that my CYA level was in fact too high. So I drained about 5", filled and went back to the pool store to purchase a calcium increaser and have the water tested again. This time I got:

FC +5

TC +5

PH 7.6

TA 120

AA x

CYA 90

CH 60

salt 4,000

phos 1,000

Again, they wanted to sell me a bunch of products to "aggressively" attack the algae problem and lower phosphates. I told the clerk that I believed reducing the CYA would allow the chlorine to be effective and I wanted to do that before purchasing any products. She said, "In my professional opinion, that isn't true. Reducing CYA won't help the algae problem." But this is the same clerk who had no idea why the pool was scaling and didn't understand the chemistry of phosphates and why the product she wanted to sell me to reduce phosphates would work.

I have NEVER put a stabilizer in this pool. I have a 17,000 gallon fiberglass, with salt water generator and cartridge filter. I keep the filter clean, and balance PH, TC and TA but don't check anything else other than the salt level (which is provided by the SWG system). We had a lot of rain this summer, so had to drain off several inches of water 4 or 5 times. As a result of draining water, we had to add salt to the pool to keep our levels correct. I suspect our problems were caused when my husband purchased salt pellets (perhaps meant for a water softener) which must have had inert ingredients that caused the low calcium and high phosphate levels. I have in the past used chlorine tabs in the winter (when I shut off the SWG) so that might have caused some of the phosphate problem, but I've always used tabs in the winter, so don't think that alone would account for such a high phosphate level.

My question is this. The local pool store told me to put 10 pounds of calcium increaser in, then a bunch of Phos Free and other products to reduce phosphates, then about $100 worth of algae treatment. Do you think the calcium is the cause of the white slime, and do you think I really need to reduce the phosphates now, considering they dropped 1500ppb by simply draining off 5" of water? Or should I drain more water to reduce CYA and phosphates even further?

I purchased the calcium increaser from the pool store, but nothing else.

[waterbear]

The phosphates are a non issue but I question where the high CYA reading came from. For a salt pool it might not be that high at all. How is the store testing and do you also test your own water? My suggestion is to get a Taylor K-2006 test kit and start testing your own water. What kind of satl generator do you have?

I have NEVER put a stabilizer in this pool.

You state below that that you use trichor tabs in winter. For every 10 ppm FC added by trichlor you also add 6 ppm CYA so, in effect, you are adding stabilizer.

I have a 17,000 gallon fiberglass, with salt water generator and cartridge filter. I keep the filter clean, and balance PH, TC and TA but don't check anything else other than the salt level (which is provided by the SWG system). We had a lot of rain this summer, so had to drain off several inches of water 4 or 5 times. As a result of draining water, we had to add salt to the pool to keep our levels correct.

If you have to add salt then you also have to add CYA! Outdoor salt pools need a certain CYA level. It is best to run the CYA at the manufacturer's maximum recommendation, usually 80 to 100 ppm, and run the minimum FC at 5% of the CYA (4 to 5 ppm) You need to be testing FC, NOT TC (so it seem syou are using an inexpensive test kit that only has OTO, pH and TA tests).

I suspect our problems were caused when my husband purchased salt pellets (perhaps meant for a water softener) which must have had inert ingredients that caused the low calcium and high phosphate levels.

Nope, not the problem, Salt pellets for water softeners are fine to use. If per chance you put in the iron reducing ones these might have caused a temporary chlorine demand problem (because of the citric acid added to the pellets to remove the iron) that could have cause an algae outbreak but it has nothing at all to do with either the calcium or phosphate levels in the water (well, perhaps they made a very small increase n phospahte because the iron out type of salt pellets do contain about .03% sodium hexametaphosphate, if you are adding enough salt for a 100 ppm increase that would be a 3000 ppb increase in phosphate BUT if you are maintaining proper FC levels then phosphates are a non issue and phosphate removers are more problem then phosphates in the vast majority of cases! Don't waste your money on them!

I have in the past used chlorine tabs in the winter (when I shut off the SWG) so that might have caused some of the phosphate problem, but I've always used tabs in the winter, so don't think that alone would account for such a high phosphate level.

Nope, no effect on phosphate at all! Trichlor will cause CYA to increase, as I stated above. Phosphates come form fill water, metal removers, and some other pool chemicals, and other sources but are a non issue. Phosphates only became an issue when someone began to market lanthanum salts as 'phosphate remover'. Lanthanum salts were very cheap and this was a high profit product. The cost of lanthanum salts has skyrocketed and they are no longer as profitable so companies are now starting to move away from the phoshpate buzzword to 'biofilm' and products are appearing to combat 'biofilms', the NEW scourge of swimming pools!

My question is this. The local pool store told me to put 10 pounds of calcium increaser in, then a bunch of Phos Free and other products to reduce phosphates, then about $100 worth of algae treatment. Do you think the calcium is the cause of the white slime, and do you think I really need to reduce the phosphates now, considering they dropped 1500ppb by simply draining off 5" of water? Or should I drain more water to reduce CYA and phosphates even further?

First, what is the recommended maximum CYA for your make of SWCG? If you don't know post the make and model and I could probably tell you. Second, get a good test kit (general consensus is that would be a Taylor K-2006 with the FAS-DPD test method for chlorine, not the K-2005 or other test kit. Spend the money on it. It is worth every penny spent!

If the pool is green you need to shock with chlorine I would suggest liquid chlorine or bleach since this is exactly what your SWCG is producing so it will have no side effects. How much you need to add depends on the current FC level. 5+ tells us noting at all! we need a number (another reason for the FAS-DPD chlorine test. It can test up to 50 ppm with an accuracy of either .5 or .2 ppm--much easier and more precise than diluting the pool water sample with distilled water and testing then multiplying the test result to get an approximate results).

We really need a good set of test reults. You have not provided that yet.

I purchased the calcium increaser from the pool store, but nothing else.

As far as calcium in a fiberglass pool--there are two school of thought--one that it is not needed at all (like a vinyl pool) and one that is helps prevent cobalt spotting and iron staining. I am in the second group because I have personally observed fiberglass pools that had low calcium and staining problems that became much less severe or stopped when the calcium was increased (including my own fiberglass pool). Caclium is needed in plaster and aggregate pools since calcium will leach out into the water if the calcium saturation index of the water is too negative but calcium is not needed at all in vinyl pools.

As far as the substance in the filter and coating the poolit could be a number of things:

If you have used a phosphate remover in the past it would be the lanthanum carbonate precipitated

If you had high TA and CH and had a pH spike (NOT uncommon in a salt pool, particularly with a TA as high as yours!) then it could be calcium carbonate precipitating out. This would cause a drop in measured CH and TA but since we don't have a history of test results there is no way to check this.

If your local water has very high magnesium hardness then it could be precipitated magnesium scale, which is softer than calcium scale. You would need to know the calcium hardness AND magnesium hardness of your fill water. Also, some 'salt cell' cleaners are magnesium salts so magnesium scale forms on the cell, which rinses off much easier than calcium scale so it you have ever used such a product then it could be a prossible source of the problem.

However, you stated the problem began when the weather cooled and the pool turned green so I suspect it might just be a lot of dead algae that had settled on pool surfaces and in the filter. Without knowing acutall CYA and FC levels it's hard to say more.

[chapinSC]

First, thank you for your reply. I do test myself, but thought the pool store would be more accurate. I have ordered the Taylor 2006 kit you recommend, but in the meantime, here is what I got testing today:

FC 2

PH 7.8

TA 90

My SWG is a Goldline, and the cell itself has T-cell-5. The control unit is an Aqua Rite 20. I went to the manufacturer's web site and their specs show:

FC 1-3ppm

PH 7.3 - 7.6

TA 80-120

CYA 60-80 (80 best)

calcium 200-400

From what I could see, the pool store (Leslie's) used a combination of drop testing and strip testing. According to their last test my CYA was 90, so not too far off the SWG recommendation.

Concerning the white chalky substance; I did have a PH spike (my mistake - I added too much baking soda), so perhaps that's it. You mention having a high TA, but I was told early on to maintain a TA over 110, so have always kept it between 110 and 120. That's also recommended by the SWG mfg. Is this a mistake?

I have always tested my pools myself, and keep the chemicals in the recommended ranges, but sounds like I'm not testing all the chemicals I should. Would you please tell me which tests I should be doing, and the recommended levels for a fiberglass pool?

And lastly, should I wait to put any liquid chlorine in the pool until my K-2006 test kit arrives next week?

Thank you!

[waterbear]

The higher the TA the faster the pH will rise because the faster CO2 will outgas. It's complicated but with a SWCG the pH will be more stalbe if the TA is around 70 ppm AND the CYA is at 80 ppm and you do not lower the pH below 7.6 and do not let it climb aboe 7.8 (easier to do than you might think!)

t

[chapinSC]

To update my post, I purchased the Taylor K-2006 test kit as suggested. I discovered through research that, in opposition to the pool store professional's opinion, very high CYA levels do cause chlorine to become ineffective, so the high CYA level was in fact largely the cause of the algae.

I took the advice of "Village Idiot ;)" and increased my CH. I also drained (over time) probably half of my pool water. I now have absolutely no staining and the pool is a beautiful, bright white. The chalky substance is also gone, and could have been dead algae or calcium phosphate as suggested.

We've had monsoons this summer (2013), and have had to drain probably 12" of water the past two months which has made pool chemistry interesting. Draining so much water lowered the salt level, requiring 4 bags of pool salt. With TA of 70, TC 3ppm, CH 60ppm and CYA 35 I have no stains, but am battling PH bounce, probably because of the low TA. I intend to increase my CH closer to 200 but plan to leave CYA and TA low for now.