scale buildup in cells of intellichlor IC40, needs frequent acid wash

[bgrinstein]

After 4 years of working with little need for cleaning, my intellichlor IC40 now requires frequent (about every 1-to-2 weeks) acid wash else it will not produce chlorine. The reason is pretty obvious, it builds up significant amount of minerals between the plates, near the top and bottom edges.

This photo shows the scale buildup view from top https://flic.kr/p/pa9cbU
and this one from bottom https://flic.kr/p/pa8Qu2

These two photos are after washing with acid: https://flic.kr/p/ppB29s and https://flic.kr/p/prCT5e

Note that the most central plates in the cell, where most buildup occurs, have been eaten away (best seen in photos after washing ).

Where do I start looking for the reason for this. Chemistry (my PH is fine I keep it 7.5-7.8)? Chlorinator (rotten cells)? Any help is welcome.

 

[JamesW]

A full set of test results, including water temperature, would help us help you.

 

[Chuckiechan]

You are probably high on one thing or another. Your test results will help zero in on your issue.

I was able to find a hose nozzle with sufficient pressure to clean my cell without acid. Bed Bath & Beyond sells a "as seen on TV" type nozzel that may also do the trick.

I've been able to avoid acid of all types since conventional wisdom is Muraitic acid is bad and vinegar is safe but slow.

 

[bgrinstein]

A full set of test results, including water temperature, would help us help you.

Here we go, from my local pool store:
FAC: 5
TAC: 5
pH: 7.5
TA: 100
AA: 100
CYA: 20
Calcium Hardness: 400
salt: 3400
phosphates: 100

The chlorine seems high but that's intentional: I ran it at high all day yesterday since it had dropped low since I had postponed cleaning the salt-cell a bit.

I have had the problem for the better part of the year, during which the water temperature has changed from low 60s to low 80s (pools stay open during winter in Southern California)
Looking forward to your advice
B

 

[JamesW]

Your current numbers don't indicate a big risk for scaling. However, with your TA so high, I would suspect that the pH frequently gets high, which could lead to scaling.

The roughness on the plates increases the risk of scaling because it creates a surface more conducive to holding scale.

If the plates are damaged in such a way as to prevent cell reversing, then buildup would not be reversed as designed.

Also, if the cell is after a heater, then the water would periodically be hotter, which increases the CSI and increases the risk of scaling.

I would suggest lowering the TA to about 60 and increasing the CYA to about 60.

 

[bgrinstein]

Your current numbers don't indicate a big risk for scaling. However, with your TA so high, I would suspect that the pH frequently gets high, which could lead to scaling.

The roughness on the plates increases the risk of scaling because it creates a surface more conducive to holding scale.

If the plates are damaged in such a way as to prevent cell reversing, then buildup would not be reversed as designed.

Also, if the cell is after a heater, then the water would periodically be hotter, which increases the CSI and increases the risk of scaling.

I would suggest lowering the TA to about 60 and increasing the CYA to about 60.

How can I tell if the plates are damaged in such a way as to prevent cell reversing? Also, if they are damaged, can I replaced the damaged plates only (as opposed to replacing the whole chlorinator, which is a hefty expense)?

 

[prs]

Here we go, from my local pool store:
FAC: 5
TAC: 5
pH: 7.5
TA: 100
AA: 100
CYA: 20
Calcium Hardness: 400
salt: 3400
phosphates: 100

If you read thru the posts on the "Just Getting Started" forum you will find that test results from pool stores are often worthless, and will lead you to make decisions that are usually wrong and expensive.

Buy a decent test kit and find out for yourself if your water is truly balanced and your CSI is is where it should be.

 

[Jkbr78781014]

I am not getting CL reading. Pentair told me to acid wash cell regardless of scale build up. The cell is 5 years old and on 8k hours so this is a last ditch effort.

here are my most recent results. I have been at 100% output for 1 month straight.

i have 23k pool and installer put in IC20. It lasted so long can’t complain but should have ic40 when I replace.

Trying to just buy time maybe get to end of Summer.