Cleaned Jandy SWG for first time

[ChristopherDB]

It's been almost 7 months since my pool was constructed and the SWG was turned on. It is a Jandy PLC1400. Pump runs 24/7. At night just at 1100 RPMs which is enough flow for the SWG. It was set to 20% output but is reduced down to 10% now that it is colder out in Florida.

I cleaned it for the first time and was surprised by the amount of buildup. I mixed 1 part acid 10 parts water and let it sit for 20 minutes until it stopped bubbling and then washed it out. There was still a lot more buildup so I increased to 1 part acid 5 parts water and let it sit for another 15-20 minutes until it was close to no bubbling and washed it out.

Im concerned if I'm going to have this type of buildup and I need to clean every couple months that the acid is going to kill the useful life of this SWG. Should I be concerned? Is there anything preventative I can do to stop this buildup?

Pool is plaster and since it's new, Im adding 1/2 gallon or acid per week to keep PH down. I check all points with the TF100 once a week and check PH and Chlorine 3 times a week. Here's where I've been keeping the chemicals at:

Chlorine: 5-10
PH: 7.5
TA: 60-70
Salt: 2900-3300
CYA: 75
Calcium Hardness: 350-400

Attached is photo.

Also, when I unscrew the unions it it hits the 2.5" coupling and doesn't clear enough room to remove the SWG, so I have to try hard and bend the PVC and pop out the unit. What a PITA it was getting back in. I'm concerned flexing all that pipe to jam the SWG back into place will eventually cause a failure in a joint. Is it supposed to be so difficult to remove? Attached is photo showing the union on one side with very little clearance to the left because it hits the elbow. The other side is the same.

 

[ajw22]

Yes, you should be concerned with the acid cleaning reducing the life of your cell.

What is your CSI?

Try lowering your TA a bit more and possibly adding borates to the pool.

TA does need to be adjusted down with an SWG. The problem is, INSIDE the cell, the CSI is very different than in bulk pool water.

With high TA and aeration from the bubbles the SWG creates, you'll get faster pH rise inside the cell and so there's more potential for scaling. With current reversal, the cell tends to stay clean but you'll get more snowflakes out of the returns. Calcium hardness is only one part of the equation.

If the SWG cell pH rises much above 10 (and it can easily do that) and if there is sufficient levels of carbonate ions available (CO3--), then you will get calcium carbonate precipitation. The higher the TA and pH, the more carbonate anions are available.

Borates are particularly helpful preventing scale in a SWG because the pKa for boric acid / borate anion buffering is approximately 9. That essentially means you get the maximum buffering capacity at a pH of 9 and that tends to hold down the pH rise inside the cell. Keeping the pH below 10 in the SWG cell reduces the risk of calcium and magnesium scaling (insoluble magnesium hydroxide precipitates at a pH of 10.2 or so).

Borates in pool - Further Reading

www.troublefreepool.com

 

[Bperry]

It's been almost 7 months since my pool was constructed and the SWG was turned on. It is a Jandy PLC1400. Pump runs 24/7. At night just at 1100 RPMs which is enough flow for the SWG. It was set to 20% output but is reduced down to 10% now that it is colder out in Florida.

I cleaned it for the first time and was surprised by the amount of buildup. I mixed 1 part acid 10 parts water and let it sit for 20 minutes until it stopped bubbling and then washed it out. There was still a lot more buildup so I increased to 1 part acid 5 parts water and let it sit for another 15-20 minutes until it was close to no bubbling and washed it out.

Im concerned if I'm going to have this type of buildup and I need to clean every couple months that the acid is going to kill the useful life of this SWG. Should I be concerned? Is there anything preventative I can do to stop this buildup?

Pool is plaster and since it's new, Im adding 1/2 gallon or acid per week to keep PH down. I check all points with the TF100 once a week and check PH and Chlorine 3 times a week. Here's where I've been keeping the chemicals at:

Chlorine: 5-10
PH: 7.5
TA: 60-70
Salt: 2900-3300
CYA: 75
Calcium Hardness: 350-400

Attached is photo.

Also, when I unscrew the unions it it hits the 2.5" coupling and doesn't clear enough room to remove the SWG, so I have to try hard and bend the PVC and pop out the unit. What a PITA it was getting back in. I'm concerned flexing all that pipe to jam the SWG back into place will eventually cause a failure in a joint. Is it supposed to be so difficult to remove? Attached is photo showing the union on one side with very little clearance to the left because it hits the elbow. The other side is the same.

Those numbers put your CSI around -0.5 which shouldn’t be allowing any buildup. Do you have a log of what actual test results have been over the past few months?

 

[ChristopherDB]

Thank you both for the insight.
Since this pool is 8 months old, I'm struggling with PH and I'm constantly putting in acid every few days to keep it in check. At the same time I'm struggling with the TA and it's always on the low side, and I'm having to put in baking soda more often than I feel I should. I keep the numbers in range but it's a lot of chemicals to keep it balanced.

I just subscribed to the Pool Math app so I don't have logs from the past.
Right now my CSI is -.68. My pool builder came yesterday after I reported my overflow line wasn't working and draining the pool so they dumped a gallon of acid down the line and as a result, much of that acid must have gotten into the pool because my PH is very low. If I had PH at 7.6 like normal my CSI would be -.4 which appears to be in range.

I keep my pump running 24/7 and at night it is running at 1100 RPM so water is flowing over the SWG slowly, but enough to keep it running. Because the flow is slow, could that cause unnecessary build up of calcium because of the PH rise inside the cell that ajw22 is talking about?

Last thing, since the pool is new the SWG was not used during the first month startup but it was still in line, so could a lot of buildup have happened during that time when the pool builder was inadequately maintaining the pool?

 

[ajw22]

What is low TA that you add baking soda to raise it to what?

The higher your TA the faster your pH will rise. Rasing your TA only increases the rate you need to add acid and adjust your pH. You have yourself on the pH and TA yo-you that you will never get off.

Stop raising your TA. Let your TA find its natural equilibrium. Just manage your pH between 7.6 and 8.0.

Post your water chemistry in the format...

FC
CC
pH
TA
CH
SALT
WATER TEMP
CSI

 

[ChristopherDB]

Low would be anything under the low range of what Pool Math is suggesting. Once it gets to 40, I'll add 4lbs of baking soda to get it to 55.

If I have to add 1/2 gallon of acid every week to keep PH under 8 and don't touch the TA with backing soda, will the TA continue to drop lower and lower?

Here is a test that I just did a few hours ago;

FC: 8
CC: 0
pH: 7.8
TA: 50
CH: 400
SALT: 3000
WATER TEMP: 75
CSI: -.28

 

[ajw22]

Right now your water chemistry looks perfect.

Do you have a spa spillover or any water features running?

What is your fill water ph and TA?

Do you have an autofill line?

What % MA do you use?

64 oz of 31% MA will reduce your pH by 1.0 and TA by 16.

You should not be adding more then 16-20 oz of 31% MA to reduce your pH by 0.2-0.3, If you do not do a large reduction in pH it will not hit your TA hard.

 

[ChristopherDB]

I do have an 8ft spa spillover that operates 3 times a day for 30 minutes each.

Fill water has a TA of 50 and PH of 8 and I rarely have to fill due to rain. Fill valve is electronic that I control from my phone but not automatic.

I use 31.45% MA.

When pool builder dumped MA to clean out an overflow line, I estimated about a 1/2 gallon went into the pool based on the PH drop. It dropped to 7. It is currently at 7.8. Looking back at my cameras to see when they came, it was actually on Tuesday, so in 5 days the PH went up .8 which is right around the 1ppm drop per week that I am using 64oz of MA to fight the PH rise.

So if I'm having to lower the PH 1ppm per week, and that subsequently lowers TA by 16, I'm needing the baking soda to keep TA within range Pool Math is suggesting. Should I do more frequent additions of MA, such as a cup a day, so the TA is not affected as much? Should I just wait a week and see how low the TA will go while keeping PH around 7.6? Appreciate all the support you've been providing.

 

[ajw22]

You want a low TA. The lower the TA the less rapidly your TA will rise.

Lower your ph to 7.8, not 7.6, with small amounts of acid.

When was your pool plastered and filled?

 

[Bperry]

I do have an 8ft spa spillover that operates 3 times a day for 30 minutes each.

Fill water has a TA of 50 and PH of 8 and I rarely have to fill due to rain. Fill valve is electronic that I control from my phone but not automatic.

I use 31.45% MA.

When pool builder dumped MA to clean out an overflow line, I estimated about a 1/2 gallon went into the pool based on the PH drop. It dropped to 7. It is currently at 7.8. Looking back at my cameras to see when they came, it was actually on Tuesday, so in 5 days the PH went up .8 which is right around the 1ppm drop per week that I am using 64oz of MA to fight the PH rise.

So if I'm having to lower the PH 1ppm per week, and that subsequently lowers TA by 16, I'm needing the baking soda to keep TA within range Pool Math is suggesting. Should I do more frequent additions of MA, such as a cup a day, so the TA is not affected as much? Should I just wait a week and see how low the TA will go while keeping PH around 7.6? Appreciate all the support you've been providing.

If it’s only been 8 months since plastering, the pH will rise fast for another few months. The spa overflow is also contributing to that.

One thing to note on pH. The lower you move it away from its equilibrium point, the faster it will rise back and fight you. So if it wants to be at 7.8 and you lower it to 7, it’ll shoot up quick from 7-7.4, then rise to 7.6 a bit slower, and then 7.8 even slower. So don’t add a bunch of acid trying to move the pH very much. Just keep it in the 7’s. 7.8 is fine, even 8 is ok as long as your test kit can reliably measure it at 8 without confusing it with 8.2 or 8.4.

 

[markayash]

I also have a spa and was battling all the time to keep my PH around 7.4. Finally somebody here suggested see where it stops and it’s around 7.8 so I add a little acid every few weeks and keep it around 7.6. I don’t even measure just pour in about a cup and call it done and so far it’s worked perfectly.
I had in my mind it would climb to infinity and beyond
My TA stays around 60 and rarely changes