Balanced Water but could there be algae?

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MarianParoo

MarianParoo

0
Aug 16, 2014
4,610
Northern IL
Current test results:
FC 5.0
CC 0
PH 7.4-7.5
TA 80
CH 80
CYA 40
Borates >50

I test FC and CC daily, pH 2-3 times per week. Since opening in Spring, my FC has never dropped below 4. CC has never been over 0.5. My pH is rock solid. I use liquid chlorine as my sanitizer and twice I used dichlor when my CYA needed a boost. I also raise my filter psi by 1 using DE after each backwash.

I was having severe back pains and neglected brushing/vacuuming for about 3 weeks. I did feel the sides of the pool every night when getting my pool sample, and they were/are squeaky, not slimy.

I now have a grayish sediment that collects in little round clumps that can be almost as large as BB's on the bottom of the pool. When I brush, it dusts up and then shoots out of the returns as a fine powder, only to re-clump fairly quickly.

My thoughts are to vacuum to waste on Saturday, but am concerned that this sediment could be something more than fine dirt. Is it possible to have perfectly balanced water and have algae?
 
Usually dead algae doesn't clump up into round balls from what I've seen. It's usually not gray colored either and you really wouldn't see it coming out of the return.
Might be some DE getting back into the pool.
Nothing I see in your test results points towards organics. ?
 
Nope, no sand in the pool. When I vacuumed after my hiatus, the pump pressure did rise to 33. (I almost never go above 27-28 before back-washing). Maybe some DE shot out then....

This clumping stuff is just weird. Before I vacuum tomorrow, I will see if I can get some decent pictures of it and then research how to post them here. I am just still nervous that it's organic.
 
Daily loss 1-2 ppm. I'm not that accurate with my additions because I test daily when I'm home. When I leave town, I up-dose to accommodate a 2ppm daily loss just in case. It's windy today so the pool surface will churn up when I open the cover; not good for pics and vacuuming but will get to it when the wind settles down.
 
I use a little over 3 cups of 12.5% to raise FC by 1ppm; about 6-1/2 cups for 2ppm.... but I don't measure my additions to the ounce. I use a plastic quart measuring cup with a pouring-spout but it's not like I look for a meniscus or anything. If the level in the measuring cup looks a little over, I don't worry as long as it looks like I hit the minimum. I don't like to get splashed by chlorine ;)

I don't really think in terms of a FC goal, instead I focus on potential FC loss.

Before leaving, I test my FC, and calculate that day's requirement. I then multiply the number of days I will be gone by by 6.5 (my 2ppm number). I add both those numbers together and add that amount of LC.

The longest I have been away this year was for 4 testing cycles. So here's an example: Test says 4.5 FC. I would normally bring it to 6, so ~ 5C. Then 4 days away is 4 x 6.5 = 26C. 5C+26C= 31C. I would add 2 gallons of 12.5%. I suppose that's like saying my FC goal would be 14.
 

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Your method is not goofy and is based on what many people assume based on the thought that FC loss is linear. Unfortunately that is not the way it works, it is a percentage loss per day. In very general terms, at FC levels above normal targets the loss is greater, higher FC is not being protected by CYA to the same degree.

Thinking about this in terms of percentage loss, with a lot of assumption on my part based on your numbers above it looks like you lose 25% in a normal day (6 down to 4.5).
Using 14 as your target the first day, you would lose 3.5 ppm (25%) down to 10.5 the first day.
Start second day at 10.5ppm, lose 2.6ppm to 7.9ppm.
Start third day at 7.9, lose 2, down to 5.9.
Fourth day you start at 5.9 and lose 1.5, down to 4.4

This apparently works for you, but work the math as a percentage for longer periods away and be cognizant of potential impacts of an initial target that is too high, (beyond shock/slam levels) that could temporarily get your Ph way out of whack and potentially cause problems. Those longer periods are a good time to use tabs in a floater to provide timed release dosing as they dissolve.

You can do a search on 'FC loss percentage' and find lot more detail and input on this.
 
The only caveat to the loss scenario just described as a percentage is if the FC/CYA ratio gets low enough for algae to grow. At that point, the growth of algae uses up chlorine much more quickly since algae doubles in population every 3-8 hours so instead of a percentage loss it is an exponential loss effectively driving the chlorine to zero in a few days.
 
Whoa, thanks! If I ever get to leave town for more than a long weekend, I will change strategies! I knew there was a good reason to keep the in-line chlorinator... And yes, I will be careful if I ever do use it. Is there an advantage to trichlor over dichlor tabs for vacations? I've never used trichlor.

By the way, my weird clumps are gone. I opened the pool last night, and yea! Gone! I think it must have been the DE escaping when my filter pressure got too high.
 
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