I have slammed my pool for about a week and two days ago the water turned crystal clear. The overnight test shows no CCs. I have done the OCLT twice, but failed to read FC loss in the morning of 1ppm or less. Both times we had severe storms overnight and at least an inch or two of rain in the pool the next morning. Could overnight rain affect the OCLT?
OCLT and Rain
- Thread starter Pharmacyman
- Start date
- May 3, 2014
- 59,317
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
You can do the math to see how much it will (not) affect you. 231 cubic inches to a gallon, so
(W(ft) x L(ft) x 144 ) / 231 = US Gallons
So in my 18' x 36' pool, an inch of water = (18 x 36 x 144) / 231 = 404 gallons. In my 25000 gallon pool, that's 1.6%
1.6% variance isn't going to move the needle much on my FC test, if it was 10ppm, now it'll be 9.84ppm
Running the pump helps ensure you don't get stratification of the water where the rain water could possible sit on top of the rest of the water and skew your test (which is why I test from about 2ft down).
(W(ft) x L(ft) x 144 ) / 231 = US Gallons
So in my 18' x 36' pool, an inch of water = (18 x 36 x 144) / 231 = 404 gallons. In my 25000 gallon pool, that's 1.6%
1.6% variance isn't going to move the needle much on my FC test, if it was 10ppm, now it'll be 9.84ppm
Running the pump helps ensure you don't get stratification of the water where the rain water could possible sit on top of the rest of the water and skew your test (which is why I test from about 2ft down).
Interesting! I am running the pump at 3000 rpm 24/7 and have been over a week. I always take samples about elbow deep in the water. FC was 15.5 last night after sunset and 13.5 this morning. There is no organic matter in the pool and the water is crystal clear and has been for a couple days. I bought fresh TFP kit chemicals before opening the pool. Guess I'll try again tonight.
- May 3, 2014
- 59,317
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
You can likely run the pump at a much lower rpm if you wish. What rpm does your iChlor SWCG require to operate? Use that rpm as your base level.
Could the rain introduce organic matter into the pool that would cause the FC level to drop?
- May 3, 2014
- 59,317
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
As long as you do not have ground runoff running into the pool, or trees overhanging the pool that bird excrement can wash off from, no. Rain itself is clean, mineral free water.
- May 3, 2007
- 17,210
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Rain water can actually contain anything that is also in the air since it travels through the air on the way to the ground and collects these particles as it falls. Including but not limited to algae spores, pollen, dust and minerals. In fact, rain needs to have dust particles in order to form.
www.usgs.gov
ChatGPT
Rainwater is not pure H2O; it can contain various substances depending on environmental factors and pollutants present in the atmosphere. Here are some common components found in rainwater:
Follow a Drip Through the Water Cycle | U.S. Geological Survey
You may be familiar with how water is always cycling around, through, and above the Earth, continually changing from liquid water to water vapor to ice. One way to envision the water cycle is to follow a drop of water around as it moves on its way. Read on to learn more about the journey.
ChatGPT
Rainwater is not pure H2O; it can contain various substances depending on environmental factors and pollutants present in the atmosphere. Here are some common components found in rainwater:
- Dissolved gases: Rainwater can contain gases such as oxygen, nitrogen, carbon dioxide, and sulfur dioxide, which are dissolved from the atmosphere.
- Particulate matter: Dust, pollen, and other particulates suspended in the atmosphere can be carried down by raindrops.
- Acids: Rainwater can be slightly acidic due to the presence of carbon dioxide, which forms carbonic acid when dissolved in water. In areas with high levels of air pollution, rainwater can become more acidic due to the presence of sulfur dioxide and nitrogen oxides, forming sulfuric acid and nitric acid, respectively.
- Microorganisms: Rainwater can carry microorganisms such as bacteria, viruses, and fungi from the atmosphere or from surfaces it comes into contact with.
- Trace elements: Small amounts of minerals and trace elements can be present in rainwater, including calcium, magnesium, potassium, sodium, and various metals.
- Organic matter: Organic compounds from decaying plant and animal matter can be present in rainwater.
- Chemical pollutants: Rainwater can pick up pollutants from the atmosphere, such as heavy metals, pesticides, and industrial chemicals, especially in urban and industrialized areas.
We’ve got some pretty heavy deluges over the past couple days over here and I got lots of debris and nearly 2” of water overnight.
No rain overnight last night. Pool passed OCLT this morning (5.5 to 5.0). Pool crystal clear. CCs were zero. Thank you TFP!
reggiehammond
Gold Supporter
- Oct 4, 2020
- 1,615
- Pool Size
- 30000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
+1. Pay close attention to the FC today. If the CYA is too low for this point in the season by you, you'll be below min in no time if yesterday's loss continues.
Post up a full set of test results.
Post up a full set of test results.
Yes, I did go from 13.5 FC to 5.5 FC in one day. Maybe because of all the rain (I wasted off 7 inches) and a CYA of only 25 to begin the SLAM?? I don't know. Currently salt level is 3600, PH 7.6, TA 80. I have CYA up to 40 now, FC this morning was 1.0. Pool water is crystal clear. I had adjusted Pentair SWCG from 20% to 40% about a week ago. Should I wait until I get the CYA up to 80 before adjusting SWCG upward?
If anything you want more FC now until the CYA is protecting it. 40 CYA might be enough compared to where you were, or it's still a little short.
reggiehammond
Gold Supporter
- Oct 4, 2020
- 1,615
- Pool Size
- 30000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
You'd be wise to do an Overnight Chlorine Loss Test tonight.
Low CYA can explains FC loss, but you're all over the place. The FC of 1 this morning is far under minimum, and you do not want to raise CYA if you may need them SLAM Process soon.
reggiehammond, you say I do not want to raise my CYA?? For a salt pool on TFP is shows a CYA of 80 is appropriate. I am at 40.
Pool passed OCLT. FC after sunset was 1.0. This morning before sunrise FC=2. No ccs. I am raising SWCG output from 40% to 60% this morning.
Pool passed OCLT. FC after sunset was 1.0. This morning before sunrise FC=2. No ccs. I am raising SWCG output from 40% to 60% this morning.
Having more chlorine at the second OCLT test indicates something wrong, like the SWCG not being turned off. Its not a passing grade.
Pump shuts off at 10pm. I thought higher chlorine this morning was result of no sun at night along with too low of CYA.
Chlorine doesnt increase naturally, it only decreases. Eithet chlorine got added after the first test or one of the tests had an error counting drops. The OCLT also needs to be started when the FC normals are above normal range. Starting at 1ppm isnt normal.
Chlorine got added after the first test via SWCG. The pump ran with the SWCG running until 10pm. This was my mistake. I believe that is why the FC was higher this morning. I will wait until FC is up over 3 and redo the OCLT.