White film on sides - algae, calcium or bacteria?

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YonnyPiscinas

Well-known member
Jan 10, 2020
141
Uruguay - SA
Hi all,

We're just coming out of winter and performed some basic tests and cleaning on our fiberglass pool.

We noticed there was a white film on the sides when wiped with our hand. See photo attached.
Not sure what it is exactly after reading some articles. Calcium deposits, fiberglass breakdown, type of alge or bacteria?

Pool covered most of the time. Crystal clear water.

FC: 0.5 (increased the SWG to max today). Most of the winter its been at about 3-5 so a big drop in the last few weeks. My fault for not checking.
CH: unknown
PH: 7.0-7.2
TA: 80-90
CC: unknown but water has zero smell of typical CC.

Pump running about 7 hours a day for the last few weeks (sun collectors on).

Temp of pool: 26c (risen 6c in the last week due to the sun collectors on and sun levels increasing)

Sorry my testing kits are basic. TA and PH look ok. FC is too low.

Is it not safe to swim until this has been eradicated? If its just Calcium then should be ok but if it's a bacteria I'll need to shock it I assume before anyone gets in.

Any advice would be appreciated.

Thanks
 

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I do not believe this is bacteria or anything pathogenic. So swim as desired. :swim:
It is possible that it is calcium- is your fill water known to be hard?
The lack of a proper test kit is obviously a huge issue, but I do understand your limitations due to locale if that is the reason.

Lets invite @Texas Splash in as he's had issues with white on his fiberglass....but I'm not sure if they could be rubbed off as you're doing.

Maddie :flower:
 
If you search our forum for chalky sides on Fiberglass (FG) pools, you'll two general responses - those whose wiped-off easily by hand and those whose seemed embedded and had to be aggressively removed (like mine). In most scenarios, the reason was unclear. In some, chemistry did in-fact play a role. While your chemistry looks like it could use some adjusting to prevent algae, I doubt the white is algae or calcium. I suspect it's something related to the gelcoat itself. While typically we say calcium isn't a huge consideration for FG pools because they are not constructed from plaster, I think it would be good to know your CH level. Your pH being on the low end normally should not be an issue, but you might let it rise a little to the 7.5 - 7.8 range. Those owners who had white that wiped off found relief by letting their TA rise a little higher, but for us a TFP we don't understand why that would be. I think some gelcoats, either from manufacturing or application, may be more susceptible to certain changes. You might also try leaving the pool uncovered a bit more to see if that helps. Some FG salt pools with a cover have been known to see oxidation at higher rates if the chemistry was a bit unbalanced. You have the advantage of having a white film that wipes off, so I would rub as much off as you can then try some of those changes above to see if that prevents its return. It may be a bit of trial and error.
 
I also forgot to mention earlier that you didn't post your stabilizer (CYA) level. That's important for a couple reasons. First, to avoid algae down the road you want to keep the FC balanced to the CYA as noted on the FC/CYA Levels. The other reason is that stabilizer is very important to serve as a protector or sorts (buffer) to the chlorine on surfaces and swimmers. A pool with low or no CYA means the chlorine will be exceptionally harsh.
 
Texas Splash said:
If you search our forum for chalky sides on Fiberglass (FG) pools, you'll two general responses - those whose wiped-off easily by hand and those whose seemed embedded and had to be aggressively removed (like mine). In most scenarios, the reason was unclear. In some, chemistry did in-fact play a role. While your chemistry looks like it could use some adjusting to prevent algae, I doubt the white is algae or calcium. I suspect it's something related to the gelcoat itself. While typically we say calcium isn't a huge consideration for FG pools because they are not constructed from plaster, I think it would be good to know your CH level. Your pH being on the low end normally should not be an issue, but you might let it rise a little to the 7.5 - 7.8 range. Those owners who had white that wiped off found relief by letting their TA rise a little higher, but for us a TFP we don't understand why that would be. I think some gelcoats, either from manufacturing or application, may be more susceptible to certain changes. You might also try leaving the pool uncovered a bit more to see if that helps. Some FG salt pools with a cover have been known to see oxidation at higher rates if the chemistry was a bit unbalanced. You have the advantage of having a white film that wipes off, so I would rub as much off as you can then try some of those changes above to see if that prevents its return. It may be a bit of trial and error.
Click to expand...
Thanks very much for the advice.

I wiped quite a bit off last night - obviously the water is still cloudy now.

I had the SWG running all night so now the FC is at a healthy 3ish
Ph still on the low side so I added some baking soda now to raise both TA and PH as you mentioned.

I'll get the covers off for a few hours each day to see if that helps also.

I have a CH meter somewhere in the house (after a house move) - still looking for it. Hopefully I can measure the hardness with it.
 
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Just measured the hardness and comes out at around 300 ppm.

Unfortunately I have not found any test kits on the market for CYA here yet. I will enquire at a couple of places but usually if they are not on the websites then they do not import them.
So CYA is a big unknown.:(
 

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So the DE powder is just added slowly to the skimmer to be sucked into the sand filter? Is this the process?
Seems to be a lot of DE powder available for gardens here but not for pools. If its 100% pure is this the same product to use? Seems to be used as an organic insecticide.
 
No, that is NOT the same product. Pool DE has been sterilized, whereas garden has not. Do not use that.

If the pool is clearing let it keep on as it is. It just takes time. DE might have helped speed it up but it can manage without it too.

Maddie :flower:
 
Prickly said:
This thread might be helpful:

White chalky residue on fiberglass pool

Ok, figured as much - just couldn't figure out how Liquid Chlorine would do any damage to a gel coat - chlorine is chlorine, etc. Thanks for the clarification.
www.troublefreepool.com www.troublefreepool.com
Click to expand...
Many thanks! Interesting read.

A few things seem to point to the gel coat - pool must be 12 yrs old now.
I had a month or 2 in winter where the FC level rose significantly while the new cover was on all the time. This may have been a contributing factor.
FC is around 1-2ppm now.

Really hope the FG lining is not failing on us (there are 2-3 very small holes where the FG fibre shows but these were there when we moved in).
Had the house for just 2 years now and still putting a lot of money into it. Last thing we need now is a costly pool repair.
 
YonnyPiscinas said:
Many thanks! Interesting read.

A few things seem to point to the gel coat - pool must be 12 yrs old now.
I had a month or 2 in winter where the FC level rose significantly while the new cover was on all the time. This may have been a contributing factor.
FC is around 1-2ppm now.

Really hope the FG lining is not failing on us (there are 2-3 very small holes where the FG fibre shows but these were there when we moved in).
Had the house for just 2 years now and still putting a lot of money into it. Last thing we need now is a costly pool repair.
Click to expand...
My fiberglass manufacturer recommends a minimum of 350 ppm calcium hardness otherwise the water can leach calcium out of your coating. Are you able to take a water sample to a pool store to test for that if you don't have a test kit?
 
Still struggling with the milky water I'm afraid. I've now got the filter on an extra 6 hours during the nightime.
Doing a backwash of the sand filter every few days. As I have not found any DE here then this may take a long time. Will have to start adding salt with all the backwashes now.
 

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