Salt Cell clogging up in days

BrianWithAY

Member
Apr 17, 2021
9
Dallas
Cleaned my salt cell (Soaked in 1:4 Acid to water)
Looked Clean.
2 Weeks later it was clogged back up.

Got the report in the attachment, Added 2 containers of conditioner, 1 container of muriatic acid.
Bought a brand new cell.

2 Weeks later it was clogged.
These images are 2 weeks post cleaning.

In 11 years of owning this pool I have never seen this.

Pool is 20,000 gallons.
 

Attachments

  • 20210730_075700_resized.jpg
    20210730_075700_resized.jpg
    123.1 KB · Views: 59
  • 20210730_080448_resized.jpg
    20210730_080448_resized.jpg
    307 KB · Views: 47
  • 20210730_081053_resized.jpg
    20210730_081053_resized.jpg
    140 KB · Views: 58
  • 20210730_082949_resized.jpg
    20210730_082949_resized.jpg
    152.3 KB · Views: 62

UKjames

Silver Supporter
May 1, 2020
214
United Kingdom
Pool Size
44000
Surface
Vinyl
Chlorine
Liquid Chlorine
Hi welcome to TFP.

I think your water chemistry maybe slightly off. However, To tell for sure what the problem is you need to get a test kit that will give accurate results that the experts on here (and you) can trust. To do this TFP recommend a Taylor’s K-2006C (the one with FAS-DPD) or TF100 You can find a link on this site too buy one.

Once you do that post up a suite of results and download the pool math app.

When you have an accurate base line you’ll get some advice on how optimise your water to prevent the swcg scaling up
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
17,528
Evans, Georgia
Wow.. If I were to believe those pool store numbers (and I don't) you should be having more problems than you mention. It appears you're having a reaction possibly between your high pH and the calcium that the SWG plates, but I could be wrong. It has to do with your CSI number, which you can manage via the PoolMath app and your testing.

Your biggest problem is relying on Leslie's to test for you and tell you what you need. Here at TFP we expect the owners to test themselves as no one cares to get it right more than the owner. Right??

And with the help of PoolSchool and the PoolMath app owners learn why they need to add x chemical and why they don't need y chemical. We learn how the chemicals work together, and what will happen when we add them.

No pool store potions either- the basic same chemicals you buy at the market. Dirt cheap compared to a pool store.

Get your self a test kit- either the TF-100, www.tftestkits.net or the Taylor K-2006C. Get your chemistry in line with good testing.
 
Last edited:

BrianWithAY

Member
Apr 17, 2021
9
Dallas
Cleaned the cell. Got the Ph correct, 4 weeks later, it is 100% clogged.
I think it is time to turn my pool over to a pool company.

I cannot believe for 10 years I have had no issues with this pool.
Couple times a year, I toss some acid in and toss some salt in.
 
  • Like
Reactions: JeanZ1

proavia

LifeTime Supporter
TFP Guide
Feb 6, 2015
2,499
Chandler AZ
Pool Size
12300
Surface
Plaster
Chlorine
Liquid Chlorine
Post a full set of current test results from one of the recommended test kits.

FC
CC
pH
TA
CH
Salt
Water temp

Test Kits Compared
Read thru ABCs of Pool Water Chemistry
Read thru Recommended Levels
Use the FC/CYA Chart
Use PoolMath

Unless you are testing your pool water using one of the recommended test kits you really have no idea what your true test results are.

With a saltwater pool, it shouldn't take more than 5 minutes three times a week to test your pool water - once you get your numbers dialed in.
 

BrianWithAY

Member
Apr 17, 2021
9
Dallas
So I got this kit but the instructions are not so simple to understand.
I don't think I am an idiot but 3-4 attempts to go through this and I am thinking of just getting a pool guy.

Any youtube channel recommendations that make this process easier to understand?
I have maintained this pool for 11 years using only the red drops, yellow drops and the salt indicator.
I don't know what has changed that it is going south on me. I now have strange colored algea sploches, the cell is clogging at light speed and Leslies recommended I add conditioner, and acid which I did but in 5 days the PH is back up to 8.

Sorry I am frustrated and somewhat impatient.

Back to the kit. The instructions are written by pool experts so there is a lot of translation for "newbies" that is getting lost on me.
 

Attachments

  • pooltestkit.jpg
    pooltestkit.jpg
    226.5 KB · Views: 13

BrianWithAY

Member
Apr 17, 2021
9
Dallas
I think conditioner is low so all my chlorine is getting lost.
I was Well below 30 so I started there and added the recommended amount and also got some acid to lower the PH.

Tomorrow I am going to re run through these tests as best as I am able.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,983
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
You have a K2005 test kit. A good kit, just missing one very important test, the FAS-DPD test for FC/CC. So you need to order that kit to complete what you have.
Here is the Taylor Youtube for the K2006 (which has the FAS-DPD) K-2006 Completeâ„¢ Kit with FAS-DPD - YouTube

All the other tests are the same. You have a DPD color match kit for FC/CC testing. OK for approximate results, but plan to get the proper FAS/DPD Chlorine & CC's test kit soon.
 
  • Like
Reactions: BowserB

BowserB

Silver Supporter
Jul 29, 2018
635
"Old" Katy, TX
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Brian, I know several people who are happy with their pool guy. They are happily ignorant of the chemical condition of their pool water. In all honesty, I don't see how it is possible to maintain a swimming pool with a once a week visit. Nonetheless, I do not challenge by happy friends with pool guys. I will not swim in their pools, however, and if any asked to swim in mine, I'd have to insist on washing their bathing suits first--to make sure I didn't introduce something undesirable into my pool.
 

Enjoying this content?

Support TFP with a donation.

Give Support

Phookinl

Member
Oct 11, 2021
10
NSW Australia
Hi Brian,

the deposit forms because calcium carbonate drops out of solution in the cell. Calcium carbonate is less soluble at higher pH and at higher calcium concentration and at higher alkalinity. The plaster surface of your pool is also a calcium compound. So to keep it from getting damaged, you need to balance the calcium hardness, the pH and the total alkalinity to keep the calcium saturation index (CSI) around 0 or a little negative I think the recommedend range is 0, +/- 0.6. I aim to keep it slightly negative. That way you get less deposits in your cell and keep the plaster in good condition.

The calcium carbonate forms in the chlorinator because the chlorinator forms chlorine on one set of plates and hydroxide ions at the other set of plates. The chlorine forms hypochlorous acid so the acid and base even out, but you get a temporary increase in pH at the surface of one set of plates while all that chemistry does it's thing. If you're pH is already high going into the cell then the scale forms really quickly.

One problem with test kits and the kids (and some grown ups) doing tests in pool shops is that they are mostly using colored dyes to indicate the results. Even in the fancy new instruments. Some of these dyes are pH sensitive so if the pH is high, many of the tests can be just plain wrong. So the first order of business is always to get your pH right. Then test everything else. If the pH is really high, it may take a couple of additions of acid before you even see a change in the test. It's not that the test is wrong, just it's maxed out and showing the highest result it can.

I suspect that your pH has been over 8 given the amount of scale that you've been seeing but the colorimetric tests most test kits use don't really give you that detail.

Running at a slightly lower alkalinity will help to keep the pH from drifting up. I tend to aim for about 90.

It's sometimes helpful to add some epsom salts to the pool as this ties up some of the calcium and stops it playing nasty games with the carbonate in the chlorinator. The scale formed is usually softer and easier to clean off as well. About 0.83 lb(13oz)/1,000 gallons ( think that's right it's 1kg/10,000L in metric). There are also chemicals called scale inhibitors that can be added, but if you control the water chemistry then you shouldn't need them.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
18,471
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
It's sometimes helpful to add some epsom salts to the pool as this ties up some of the calcium and stops it playing nasty games with the carbonate in the chlorinator. The scale formed is usually softer and easier to clean off as well. About 0.83 lb(13oz)/1,000 gallons ( think that's right it's 1kg/10,000L in metric). There are also chemicals called scale inhibitors that can be added, but if you control the water chemistry then you shouldn't need them.

Honestly, this is terrible idea. Epsom salt is magnesium sulfate. Magnesium ions are highly soluble in water and while they add to the general hardness, they will not scale out of solution. Sulfates are terrible to add to a pool for a couple of reasons - calcium sulfate scale (gypsum) will form and that is completely insoluble even in very strong acids. Calcium sulfate scale may be "softer" than calcium carbonate scale but it adheres to material surfaces just as strongly and cannot be easily removed except by glass bead blasting. As well, sulfates attack the transition metal coating on SWG plates leading to early failure. Most SWG manufacturers warn against using dry acid for pH control for this very reason. Finally, at high enough concentrations, sulfates attack concrete surfaces and metal equipment (ladders, handrails, etc) leading to advanced forms of corrosion. TFP never recommends using sulfates of any kind in a pool.

While I understand the use of magnesium salts is very popular in Australia and other countries, it is not recommended for pools. It does more harm than good and does not help with the control of carbonate scaling in any meaningful way.
 

Phookinl

Member
Oct 11, 2021
10
NSW Australia
Honestly, this is terrible idea. Epsom salt is magnesium sulfate. Magnesium ions are highly soluble in water and while they add to the general hardness, they will not scale out of solution. Sulfates are terrible to add to a pool for a couple of reasons - calcium sulfate scale (gypsum) will form and that is completely insoluble even in very strong acids. Calcium sulfate scale may be "softer" than calcium carbonate scale but it adheres to material surfaces just as strongly and cannot be easily removed except by glass bead blasting. As well, sulfates attack the transition metal coating on SWG plates leading to early failure. Most SWG manufacturers warn against using dry acid for pH control for this very reason. Finally, at high enough concentrations, sulfates attack concrete surfaces and metal equipment (ladders, handrails, etc) leading to advanced forms of corrosion. TFP never recommends using sulfates of any kind in a pool.

While I understand the use of magnesium salts is very popular in Australia and other countries, it is not recommended for pools. It does more harm than good and does not help with the control of carbonate scaling in any meaningful way.
Yeah, it's probably what my german boss would call "sub-optimal" :). I agree with what you're saying at high levels of sulfate and with respect to the coatings on the SWG. Lets keep it in perspective though. Regularly adding sodium bisulfite to adjust pH is going to build up far higher sulfate concentrations in the water than a one off dose of epsom salts.

I respectfully disagree with the concerns about gypsum scale and I would point out that we're talking about 40ppm. It's negligible in terms of gypsum deposition potential even in a heater. As far as corrosion goes in a heater, I would leave that one to the manufacturer of the heater, but if it's built to stand up to several thousand ppm of sodium chloride I suspect it would cope fine with 40ppm of sulfate. It's going to tie up a little bit of calcium by ion pairing, reducing the saturation in the SWG slightly and it's going to add a little bit of magnesium hydroxide into any deposit in the SWG softening it and helping it redissolve when the cell isn't running and making it easier to clean.

With respect to the SWG, I would leave that up to the manufacture, but I know that mine is compatible with it and the manufacturer actually sells the material in this application at the quoted dose. As they would have legal liability if their product caused serious corrosion issues either in SWGs or in pool equipment generally, I doubt very much that they would be pushing the stuff if there was a significant risk of damage at the recommended dose.

Realistically, this is a problem that can and should be managed by properly balancing the water so in the vast majority of cases it shouldn't be necessary. There may be just the occasional person who can benefit from it, but they would be quite rare. There's an exception to every rule isn't there ? ;)

In terms of dry acid if I was to adjust the pH in my pool weekly with dry acid I would be adding around 4 ppm of sulfate, week in week out indefinitely and that will build up. 200 ppm in a year. Next year it's 400 ppm. After 5 years without partial changes, it's a gram per litre. Yes, dry acid is bad news. That will have an impact.

Probably the main reason not to do the epsom salts is that it makes it hard to keep track of what the calcium saturation index actually is. The Taylors kits are measuring calcium hardness rather than total hardnes, so they shouldn't pick up the magnesium , but many cheap tests and some pool shops do total hardness. That 40 ppm of sulfate comes with 9.4 ppm of Mg which equates to 40 ppm as CaCO3 (what the test reports). So if that is included in the calcium hardness it's going to be a noticeable source of error. Meanwhile the sulfate ties up 16 ppm of real calcium (41ppm as calcite) and I haven't seen any standard pool test kits with sulfate reagents. So while you can just subtract 41from the measured hardness when doing the CSI, that won't happen automatically in PoolMath. It will gradually bleed out with partial water changes and so on, but tracking it means buying an additional test kit.

As a one off if I was stuck, I'd do it. I wouldn't make a habit of it and there would be better options in most cases. We regularly have water restrictions here due to droughts. That makes it difficult or very expensive to do a partial water change. So some people might well end up with high hardness and running very low alkalinity levels or low pH comes with it's own problems. In that case a little mag sulfate is the lesser of two evils.