My CH was down to 120 so I added 50 pounds of calcium chloride and it only increased CH to 225 . Pool Math says 27 pounds should have done that. 50 pounds should have taken it over 300. I am pretty sure my pool volume can't be off that much. I did this with chlorine pretty high (near SLAM level) but I get the same test levels regardless of chlorine levels it drops. Can anyone tell me how this is possible? Thanks
What can cause raising CH to require double the calcium chloride Pool Math says?
- Thread starter NickJ
- Start date
- Jun 24, 2021
- 7,753
- Pool Size
- 30000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60
The pump runs all the time at a speed that should achieve one 29,000 gallon exchange per day. I have tested numerous times over the past week and get a CH of 225 every time. I used calcium chloride from Leslie's. It was in a 50 pound bag labeled by a company that claims to be the largest supplier of calcium chloride. I guess the initial measurement (120) would be more suspect since I only did it once but I was very surprised CH had dropped that low over the winter. It was well above 300 as I recall and the only water loss was back-flushing to maintain water level after rain. It does rain a fair amount here in SC but it has never done this before but I did switch to liquid chlorine a couple of years ago so it has not gotten any calcium from cal hypo since then. I guess it just caught up with me and I must have skipped the CH testing assuming hardness was holding when it was actually continuing to decrease.
Thanks. Leslie's 50 pound bag. I included this in a longer answer to another question. It was supposed to be 100% calcium chloride but I plan to dig up the bag to be sure and if I retrieve it from the trash and discover it was NOT I will post that here. It seemed to dissolve very quickly and little hit the bottom of the pool when I dumped it in and the little that did vanished when brushed.
Usually the pool store stuff is pure. You spend a ton on the fancy label, but at least it isn't all filler.
For future knowledge, folks got lucky this year with dirt cheap calcium chloride at concrete suppliers and agriculture supply stores. (Like for actual farmers, not TSC for Harry Homeowner).
For future knowledge, folks got lucky this year with dirt cheap calcium chloride at concrete suppliers and agriculture supply stores. (Like for actual farmers, not TSC for Harry Homeowner).
I discovered it was 83 to 87% not 100% as I had assumed but that would still be over 41 pounds when Pool Math asked for 27 so I am still baffled. I thought calcium hardness was one thing that stayed constant unless water was added. I have some more on order and will see what pool math says to add to raise it from 225 to 300 and report what
happens.
If anyone could explain - even a theory - what is happening I'd appreciate it. Raising Ch was one of the suggested methods of calculating a more exact pool water volume but obviously that can't work if adding 41.5 to 43.5 pounds can only raise CH as much as Pool Math says 27 pounds would.
- May 3, 2014
- 58,898
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
The pool should be brushed very well with pump running after adding items like calcium or salt. Their density is such it can settle in the deep end.
Do you think running a pool cleaner like A Dolphin with its rubber tractor like brushes helps? I have brushed but probably not as much as I should. For things that don't dissolve readily (like CYA) I put it in the skimmer and I count on the pool filter dissolving it and try to give it a week.
- May 3, 2014
- 58,898
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
The robot will help. But a good vigorous brush session really mixes the water. You state you have a 'hopper style' deep end. A great place for that higher density water to sit.
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Yes, when we bought the house (1978) the pool had a 1 meter diving board so the bottom of the "hopper" is about 10 feet deep. The reason I asked about a chemical way to determine pool volume is not entirely due the disparity in the CH I achieved when adding 50 pounds (actually 41.5 to 43.5) of calcium chloride being so much less than Pool Math projected. I also got significantly less of an increase in CYA level after putting 8 pounds in the skimmer but I did that at the start of a SLAM and could not give the filter a whole week to dissolve it before I had to back flush it (about 4 days). When I add more CYA I will make sure that does not happen. I estimate CYA at 25 since I barely see the dot at 30. Although I am an engineer and divided the pool into multiple geometric shapes (including the upside down pyramid comprising the hopper) when I calculated the volume many years ago there are so many angles and slopes that required estimating I worry it could be off but I don't think I could be off 50%.
Also, could you clarify " A great place for that higher density water to it." I did not follow. Sorry
- May 3, 2014
- 58,898
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
At 78 I am probably getting senile but I still don'y understand. There is a return (drain) at the very bottom of the "hopper" about 10 feet below the water surface. It is always open and the pump runs all the time so I had assumed that return path carried more water back to the filter than both skimmers at the water surface "combined" due to the 10 foot head at the bottom. I now take water samples from the deep end for testing several feet below water surface (using a modified product called a "back saver" that attaches to a pole). With this description of my set-up do you still think that water would be any different?
- May 3, 2014
- 58,898
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
You would need to severely restrict flow into the skimmers to get any appreciable flow from the main drain. The head is equal in both systems. The main drain has more resistance as the lines are longer.
What I stated may not be occurring. But it is an explanation to your concern.
What I stated may not be occurring. But it is an explanation to your concern.
Thanks. I think I understand. I appreciate your advice. I left out the fact my pump is is about 3 or maybe 4 feet below pool water level. (down a hill) One line from one skimmer to the pump is probably 60 feet but the other is under 20 and the line from the deep drain is maybe 25 feet. That distant skimmer has noticeably less suction as you would expect.