Overnight FC Loss

grinchman007

LifeTime Supporter
Sep 23, 2009
4
Galveston, Texas
I do not post much, since I usualy search and find answers to many of my questions. But first, I wanted to give thanks to everyone who takes the time to answer and help us new pool owners.

I am having some staining issues. At this time, I am trying to determine if they are organic or metal. Unfortunately my work schedule and the weather here in Galveston, Texas, has not allowed to me give 100% attention. We are having rain daily, sometimes a light drizzle to the, out of the blue, 10 minute downpour. I plan on taking next week off (not a vacation, but a big honey-do list) and tackling the pool staining issue is a priority. So everyone will get to know me real well then.

Anyway, my question is regarding the overnight FC loss test. My pump runs from 8 AM to 8 PM. So the pumps are completely off overnight. I have done a couple of preliminary loss tests to get the hang of things and I am showing some loss (1st test 1.5 PPM, 2nd test 2 PPM), but again, both times included an overnight rain (not hard enought to wake you up, but I can tell by the small water pools on the deck). Is it safe to assume the rain could have contributed to the loss? Also, should the pumps be running overnight to keep the chlorine circulating?

I apologize for the long winded post, but I am actually preparing everyone for the barage that will be coming next week.

Thanks, Mark
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
The pump does not need to be running overnight for the test to be valid. The pump should be running for a little while after you add chemicals and again for a little while before you take a water sample for testing.

Heavy rains can use up a little chlorine. Light rains don't usually use enough to notice. It isn't the rain so much as debris blown into the pool that uses up chlorine. So, a windy night, even without rain, can use up some chlorine, while a very calm night (no wind) with steady rain won't use up much chlorine.
 

grinchman007

LifeTime Supporter
Sep 23, 2009
4
Galveston, Texas
Thanks for the quick response Jason.

The time frames for the two tests were as follows (with last results):
9:30 PM (pump has stopped running for 1 1/2 hours) FC=10, CC=0, TC=10
6:00 AM (pump still off) FC=8, CC=0, TC=8

Should I let the pump run until 9:30 (taking my sampe before turning it off)
Turn pump on 5:00 AM and take sample at 6:00 AM.
Would this give me more accurate readings?

Is it common to have a FC loss, but CC=0. I would think if something was consuming the FC, you would have a residiual CC reading.

Mark
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
There isn't any reason to assume there will be CC. You can have algae and never see any CC.

It would be good to run the pump for about 30 minutes before taking the sample in the morning, but the results are probably fairly close the way you did it.

An overnight loss of 2.0 means you are close to getting everything, but not quite there.
 

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