Maintaining CSI in Winter, with colder water temps

Stoopalini

Gold Supporter
Jun 8, 2020
442
Central Texas
Pool Size
14060
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
As the pool water temp gets colder, I notice my CSI dropping below the target range.

My pH has been rising pretty quickly, requiring around 15oz of MA every 2 days to keep it below 8.0.

In order to keep the CSI in range with the lower water temp, should I allow the pH to stay in the 8.0-8.1 range?

Right now my CSI is -0.69 with a pH of 7.6. But at 8.0 pH, it would be -0.27. Even with a pH of 7.8, the CSI would be -0.46; which I realize is within the target range of PoolMath, but is outside the recommendation I keep seeing of between 0 and -0.30.

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ajw22

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TFP Guide
Jul 21, 2013
21,116
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Yup, let your pH rise to offset colder water. It is easier to adjust pH then TA or CH.
 

Bperry

Gold Supporter
Aug 20, 2020
99
Knoxville, TN
I have similar numbers as you, except my CH is in the 400’s. Which makes it easier to keep the csi a little higher. Though the pH is pretty stable needing a little acid about every other week.
 

Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
1,645
Rancho Cucamonga, CA
Aeration will cause pH to rise. Limit the use of waterfalls, water features, and the spa spillover to decrease aeration. Each time you add MA, your TA drops which further lowers CSI. You don't want your TA to drop any further.
 

Stoopalini

Gold Supporter
Jun 8, 2020
442
Central Texas
Pool Size
14060
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Thanks guys, I appreciate the guidance. I'll let the pH go to 8.2 max, and see how things settle.

Aeration will cause pH to rise. Limit the use of waterfalls, water features, and the spa spillover to decrease aeration. Each time you add MA, your TA drops which further lowers CSI. You don't want your TA to drop any further.
I run my waterfall for one hour each day, and that alone doesn't seem to raise the pH much. About 4-5 weeks back though, a suction side leak developed, so I'm now getting air in the pump basket. Then when the pump kicks up to high speed (2x per day), that air is pushed out of the returns as very fine bubbles. I believe this is the main culprit to my pH rising faster than prior to this suction side leak developing.

Here's a video I made for my PB, showing the issue. I'm just waiting for them to come resolve it.

But all of that said, the CSI falling out of range is really what I was trying to understand. As for the pH rise, I'll keep dosing MA, but will change my approach from dosing at 8.0 to bring it down to 7.6, to dosing at 8.1/8.2 to bring it down to 8.0 . If my TA continues to drop and hits 50, then I'll decide how to proceed (ie: raise TA with baking soda, or maybe add boric acid to provide a larger buffer for the low TA ... I've been considering adding borates anyway)
 

HermanTX

Gold Supporter
May 20, 2020
926
Katy TX
Pool Size
14600
Surface
Plaster
Chlorine
Liquid Chlorine
With regard to your bubbles. I have read on this forum that a SWCG will produce gas and show as bubbles when you are running VS at low speed. The high speed will clear them as your video shows. You indicate you have a SWCG so that could be one answer to your issue. I don't have a SWCG but search and you may find that info or maybe others can provide input to that. Also, if you want to test for suction side leaks around the pump and pipes above ground, try this technique in this video. You should keep your pump at a constant speed throughout the test to reduce variables.
Suction Side Leak Testing

 

Stoopalini

Gold Supporter
Jun 8, 2020
442
Central Texas
Pool Size
14060
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Ya, an SWCG can produce gas bubbles downstream, and you'll see them at the returns. But an SWCG can't produce bubbles in the pump basket, as it's upstream from the generator.

The air I see in the returns happens when the large air bubbles in the pump basket break up and flow downstream. I also hear loud gurgling in the buried pipes when this happens.
 

ajw22

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TFP Guide
Jul 21, 2013
21,116
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
The air I see in the returns happens when the large air bubbles in the pump basket break up and flow downstream. I also hear loud gurgling in the buried pipes when this happens.
What speed are you running your pump?

It is normal for an air bubble to form in the pump basket when run at low rpm.
 
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Stoopalini

Gold Supporter
Jun 8, 2020
442
Central Texas
Pool Size
14060
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
What speed are you running your pump?

It is normal for an air bubble to form in the pump basket when run at low rpm.
I run it at 1200 RPM 24x7, and kick it up to 2500 RPM 2x a day for one hour each time.

Where does the air come from when run at low RPM?
 

ajw22

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Jul 21, 2013
21,116
Northern NJ
Pool Size
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Where does the air come from when run at low RPM?
Your pipes are sized to be full at high RPMS and flow. At very low RPMs the water does not fill the pipe and air bubbles form along the plumbing and over time the air gets carried to where you see it in the pump basket.

When you run your pump at 2500-2700 RPM do you see air bubbles continuing after the lines are purged of accumulated air?

If you have an air leak you will see bubbles continuing at high RPM as well as low RPM.
 

Stoopalini

Gold Supporter
Jun 8, 2020
442
Central Texas
Pool Size
14060
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Your pipes are sized to be full at high RPMS and flow. At very low RPMs the water does not fill the pipe and air bubbles form along the plumbing and over time the air gets carried to where you see it in the pump basket.
But where does the air enter the system? Once the pipes are filled for the 1st time, flushing the air out ... when the pump drops to low speed, I don't see how air can be introduced unless there's a leak somewhere.

When you run your pump at 2500-2700 RPM do you see air bubbles continuing after the lines are purged of accumulated air?

If you have an air leak you will see bubbles continuing at high RPM as well as low RPM.
Yes, when run at high speeds (even after the air is flushed from the pump basket), you still see bubbles coming in; but they don't collect because the velocity is such that they flow right through the basket and don't get stuck in the ridges on the bottom side of the lid.
 

ajw22

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Jul 21, 2013
21,116
Northern NJ
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But where does the air enter the system? Once the pipes are filled for the 1st time, flushing the air out ... when the pump drops to low speed, I don't see how air can be introduced unless there's a leak somewhere.
The water coming into your skimmer is a bit aerated. At low speeds the air separates over time. That is why the bubble in the pump basket starts out small and grows over time until it stabilizes.

When you have a suction side air leak at high RPMS you see a big churn of bubbles in the pump basket and often water swirling around with the air.
 

Stoopalini

Gold Supporter
Jun 8, 2020
442
Central Texas
Pool Size
14060
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
The water coming into your skimmer is a bit aerated. At low speeds the air separates over time. That is why the bubble in the pump basket starts out small and grows over time until it stabilizes.

When you have a suction side air leak at high RPMS you see a big churn of bubbles in the pump basket and often water swirling around with the air.
Makes sense ... will that create enough air to cause gurgling in the return pipes under the decking? We frequently hear loud gurgling when air is coming out of the returns.
 

ajw22

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TFP Guide
Jul 21, 2013
21,116
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Makes sense ... will that create enough air to cause gurgling in the return pipes under the decking? We frequently hear loud gurgling when air is coming out of the returns.
Hard to say. If that area has some turns in the piping the turns can create turbulent water.