Houston, TX No-Shade Pool Owners, how much FC loss

[DanF]

So we know Kato's excessive CYA usage is either water leak or rain/splashout (or both). Water leak can be eliminated with a bucket test, correct?

 

[Katodude]

While I may have a leak now (I am checking everything since my water loss seems high), but I did not have one last summer when the CYA was dropping like crazy, and we had a span of time without much rain. Also my salt level and CH level decrease at a substantially lower rate than CYA.

There is a point in the summer where the humidity is super high. The air temp is about the same as the water temp, and evaporation in my pool basically stops. However, the CYA continues to degrade.

 

[Katygreys]

This is a great thread, at least for me. I have 50 lbs minus 1 puck (that is, 99 pucks) just sitting in a bucket in my garage doing nothing for the past few months. After reading the posts on this thread, I will definitely be monitoring my CYA more often. And if I detect loss, I will take the opportunity to throw a few pucks in based on Pool Math to get my CYA back up. Again, this has been a great thread for me. Keep it coming if anyone has anything else to add!

 

[Texas Splash]

TODAY - HOT around S.A.! Ouch. Probably about the same in H-Town. I've been dancing with my CYA for 1.5 weeks now trying to increase it for my salt pool to a solid 70. Between testing variables and questionable stabilizer, I've had to add more twice. I may take it up to 80 soon. My pool has zero shade, so the stabilizer makes a huge difference.

 

[DanF]

Someone say "hot"?

I've been trying to get my CYA increased a bit lately also. Where's that black dot? LOL. Just a reminder that the solstice is still two weeks away (highest UVs of the year).

There is a point in the summer where the humidity is super high. The air temp is about the same as the water temp, and evaporation in my pool basically stops.

I'd love for evaporation to stop here (maybe not at the expense of that South Florida humidity though). If I turn my autofill off, I can almost watch the water level go down.

 

[duraleigh]

If can pass an OCLT yet lose more than 3 ppm FC during the day, Something is not right. Your daily loss to the sun should be around 2 -2.5 ppm in FULL SUN and then perhaps as much as 1 ppm (or less) with that swimmer load and that CYA.

(Of course, as some have already posted "Yeah, me, too!) it is still not right. The long, long history (over 15 years) of reported FC loss just doesn;t support that much loss

 

[Katygreys]

So if I pass OCLT, have CYA if 60 in a bleach (not SWG) pool, what is not right?

Am I not really passing OCLT even though I think I am? Or is my CYA really 30 and not 60?

 

[DanF]

IMO...if you are truly passing your OCLT, a CYA difference of 30 vs 60 would not explain the extra FC consumption, even with a pool in full sun.

I'm in AZ, and running my Circupool RJ45+ at 50% for 6 hours/day and FC is staying pretty constant at 5.5-7.0 depending on when I test. That level of runtime, according to PoolMath, generates 2.4 ppm FC/day. That's in full sun - we apparently don't believe in clouds here .

 

[DanF]

depending on when I test

Yes I know I should test the same time everyday .

 

[Katygreys]

Interesting. Some say 2.5-3 ppm FC loss per is normal. Some say 6. That’s a big difference in dollars when you consider liquid chlorine costs. I’m befuddled.

 

[DanF]

How about we try this? Do an OCLT tonight and verify no FC loss Wednesday morning. Note your FC reading Wednesday morning. Immediately after, add 1 gallon of your Pinch-A-Penny chlorine. One hour later, measure your FC. If it's not 7 ppm higher than an hour ago, either your bleach isn't 12.5 or your pool isn't 18K gallons.

Then, 24 hours later, test FC again. Thursday's reading less Wednesday's 2nd reading is your daily FC loss. Lets have a look at that data.

Note: I just realized it's pretty late there. If you can't do the OCLT tonight, then let's do it tomorrow night.

 

[Katygreys]

I can do this. However…

- Is the purpose merely to verify if my bleach is the alleged strength? If so, I do this somewhat frequently. Last night I did it. FC was 6. I added 3 quarts 2 cups per pool math to get FC to 11 (my nightly target). An hour later I measured FC at 11.5. So I have confirmed as recently as last night that my bleach is the advertised strength.

 

[Katodude]

The OCLT will help us determine if you have algae which could be contributing to your very high FC loss.

 

[DanF]

The OCLT will help us determine if you have algae which could be contributing to your very high FC loss.

Exactly. Also, your LC addition of 112 oz should have raised your FC 6.1, not 5.5. I would say that's pretty close given your pool might not be exactly 18K gallons, and testing variation. Let us know the results of tonight's/tomorrow's OCLT.

 

[Katygreys]

Ok thx. I’ve done OCLT but I’ll do another one. Anything to reduce my chlorine usage would be great

 

[Katygreys]

Exactly. Also, your LC addition of 112 oz should have raised your FC 6.1, not 5.5. I would say that's pretty close given your pool might not be exactly 18K gallons, and testing variation. Let us know the results of tonight's/tomorrow's OCLT.

Sorry. FC was 5 (not 6). Pool Math said add 112oz to get 11. I measured 11.5 after an hour.

 

[DanF]

Or is my CYA really 30 and not 60?

It would help to test CYA also.

 

[PowerPigg!!]

I am reading all this with great interest because I also see 5ppm loss on average between sunup and sundown. This was reduced to about 2.5 ppm avg during the daytime when the last tropical system came though and the sky was overcast all day through.

I wonder what effect doing water circulation during the day vs at night might have on this. Based on what I've learned about UV chlorine degradation from this site (it increases as current FC concentration increases, and UV radiation only penetrates so far down on the water), I wonder if the higher surface concentration of FC enabled by daytime circulation exposed more of it to the particularly strong UV we see down here during summer months.

I also wonder if this is a more common issue for owners of AGP's like me if the vinyl itself allows some UV radiation through to adjacent water all the way to the lowest depth. Having more water being exposed to UV in the morning and afternoon than one would assume given an entirely opaque liner would certainly skew calculations.

 

[QingGuy]

Full sun Vegas pool here. Average 2-2.5 FC loss per day. I keep my CYA at 80

 

[BowserB]

Hello Grey. I'm in Katy--old Katy just north of Katy City Park and off Avenue D. We're on the edge of the ancient Katy Prairie, and the south wind blows here pretty much all the time, except some of the winter when it blows from the north. I've notice this year more than last at setting of 40% on my Pentair IC-40 SWCG has a harder time maintaining 6ppm FC. My approach when both FC and CYA are low is to put some tabs in a floater and the floater in the spa, which spills over into the pool. We have run the heater more than last year, and I'm sure the wind and sun take their toll. I've also this year had a lot more seed pods from nearby Purple Vitex flowering trees. Another thing you've probably heard is the Sahara dust which keeps the sky from being blue, and which also quietly settles into the pool, but other than creating a bit of mud for the the robot, I don't know about its impact on a pool or pool chemistry.

I add muriatic acid a couple times a week, but just a couple cups worth. Last drop in FC I used the floater as well as bumping the IC-40 up to 50%, and that brought FC from 5 to 9 in five days. I also put some stabilizer in a sock to get the CYA up faster than just the tabs alone. The pump runs at 1600rpm 8am to 8pm with the IC40 also running that schedule. With our mini drought, I've added water a couple times. Sometimes I overshoot with adjustments, preferring FC to be high rather than low.

Incidentally, I think I read your reference to a possible Hayward T15 SWCG being considered? The general recommendation I've read here is for a SWCG with double the capacity of your pool. I'm not familiar with the T15, but if the 15 refers to gallons, then that may be a bit small. My 15k gallon pool is running a Pentair IC40 (the 40 refers to gallons of capacity at 24 hrs a day). In winter it runs around 8-10% for ten hours. Now it's 12 hrs at 40%. You can see from my Poolmath logs the swings I've had.

Just tested again. I think yesterday's CYA must have been a mistake. Tested twice today, and it's back at 60 and FC at 7. Yesterday was at 2pm (CDT); today at 4:45, and the water temp is up to 91 from yesterday's 89. After yesterday's test, I turned the IC40 down from 50% to 40%. Wind comparable 22mph yesterday, 23mph today. It's windy here on the prairie. This may be too much info, but I'm trying to give you what I'm seeing in a similar environment.