Questionable MA injection location

[wireform]

Not pool in signature:
I'm involved in this pool as a back up to the customer to be reassured pb isn't doing anything non recommended. This pool and equipment is still under warranty so the po doesn't want to abandon them yet with Easytouch/ Intellichem. Not a fan of the intellichem system as I have many without it running perfectly well.ORP sensors is a non stop cleaning or change out issue. I find the Intellichem is constantly malfunctioning and causing non stop call outs to the pb and they're always looking for items to bill, for instance, I laid down the law of the land that nothing gets added to the water without my pre check. In one scenario they brought some gallon jug to lower the FC which was about 9-10 at the time and I said nothing doing. 10 fc isn't high and if it's high it'll come down without adding that junk.
Rant over, now the question. Pool pad is having an enclosure being built as this pool stays open all year and is also heated to the sky with the auto cover. I was doing my inspection yesterday on the ongoing work and saw something that to me may not be right. The MA injection line is plumbed right before the salt cell and that can't be correct. The first cell lasted about one year and was under warranty but something tells me now the cause may be due to the constant diluted MA passing through the plates. I'm I onto something here?

 

[mknauss]

I believe that is correct. The Intellichem will turn off the SWCG when adding acid.
@Dirk is all into that stuff ------

 

[ajw22]

Even if the Intellichem is setting the Intellichlor to 0% to turn it off before dispensing acid you have low pH water flowing through the cell. That cannot be good for the life of the SWG plates.

I would change the acid dispensing to after the SWG cell.

 

[Dirk]

Pentair specifically recommends the acid injector be placed before the SWG. It's in the manual. Though I cannot say why.

Pentair programs their IntellipH system to shut down the SWG while the IntellipH is injecting. I would expect the IntelliChem does the same thing. It's easy enough to double-check. Initiate a manual acid injection event in the IntelliChem controller and observe the SWG. Its output lights should all go off (as in 0%). If any stay on, then it's not working as expected. If they all go off, then it's working correctly.

My injector is placed as recommended, and I've had no issues with the SWG down stream. If your SWG died after a year, and the runtime doesn't account for its short life, I'd say you just happened to get a lemon.

While I agree it's counterintuitive to have low pH water running over the SWG plates, I doubt it amounts to anything. It's not like giving the plates an acid bath cleaning, or anything close. Out of curiosity I looked up some spec's. Check my math:

At about 1500 RPM a typical pool pump will push 35GPM. That's about the flow rate an SWG is going to want.
The Pentair acid pump puts out about 4oz of acid a minute. And you should only be running 1:1 acid in its tank, or about 15% muriatic, give or take. 4oz for a minute is the systems manual injection cycle, your actual setting my be pushing even less, maybe much less, but let's say 4oz.
So that's 4 oz of 15% acid in 35 gallons (4480oz) of water, which is about a 1:2240 dilution of full strength muriatic. And that's for a minute max, you're not soaking the plates in the stuff. And then, of course, they get "rinsed off" for the next 59 minutes with pool water! Even if your flow rate is half that, it's still a 1:1000 dilution. I doubt that's causing any undue wear on the plates.

 

[Dirk]

By the way, if you want to fix something, you need to move the tap for your booster pump. Right now you're sending highly chlorinated (and/or acidic) water into that pump and vac head. The SWG should always be the last thing in your plumbing before the water returns to the pool.

That tap should be between the filter and the acid injector.

 

[Dirk]

By the way part two, I see that your SWG is humping five LEDs. That's 100% output. If you are running that 24 hours a day, here's some more math:
10000 hours (best-case life expectancy of your SWG) ÷ 24 hours a day = 416 days. That's just over a year.

If that's what you're doing, your SWG pooped out pretty much right on schedule.

 

[wireform]

Pentair programs their IntellipH system to shut down the SWG while the IntellipH is injecting. I would expect the IntelliChem does the same thing. It's easy enough to double-check. Initiate a manual acid injection event in the IntelliChem controller and observe the SWG. Its output lights should all go off (as in 0%). If any stay on, then it's not working as expected. If they all go off, then it's working correctly.

Interesting though. Back in the summer I had a frank talk with the pool builder....and he told me then that regardless of what the led's show on the cell, the Intellichem decides the cell value according to the ORP and I should disregard the led's and I had to believe him as I'm a total stranger to the orp system....

By the way, if you want to fix something, you need to move the tap for your booster pump. Right now you're sending highly chlorinated (and/or acidic) water into that pump and vac head. The SWG should always be the last thing in your plumbing before the water returns to the pool.

That tap should be between the filter and the acid injector.

Not my doing but will try to work on getting this changed.

 

[Bperry]

Pentair specifically recommends the acid injector be placed before the SWG. It's in the manual. Though I cannot say why.

Maybe cause they also sell a replacement SWG. seems like a no brainer safety item to put it after the SWG especially if they are shutting down the SWG when injecting acid.

Lots of manufacturers recommend cleaning the cell with acid so adding a little acid automatically in the plumbing wouldn’t be any worse (according to their logic)

 

[JoyfulNoise]

When the IntelliChem controls the IntelliChlor it runs the SWG at 100% output until the ORP achieves set point. It doesn’t matter what you set the IC to in the EasyTouch panel, the IntelliChem is the big boss man.

And that’s exactly the problem with iChem/ORP control - it tends to not be representative of the actual FC level and so you are chasing a “ghost in the machine” which means your SWG is hammering away at 100% output while the ORP probe dances a jig.

Also, I disagree with Pentair and @Dirk regarding the acid injector but it’s what the manufacturer directs people to do and so it’s done. Acid is very bad for ruthenium coatings … doesn’t matter the concentration. Ruthenium hydrated complexes are very water soluble and they can form in oxidative environments at all pH levels below 10 or so (the lower the pH, the more thermodynamically stable they become) and chloride ions are really good at making them even more soluble (sulfates are even better at it). It’s why SWG anodes are consumable.

 

[wireform]

@JoyfulNoise
I can't agree with you more on every point and that was my concern...thanks

 

[Flying Tivo]

That cannot be good for the life of the SWG plates.

I stuck with pentair recommendation. 5 years going and no ill effect visible. I do use 15%MA which is easier on the cell. Im no math expert but dosing 230ml per minute@10GPM, its quite diluted when it reaches the cell. I do agree that Logic dictates after the cell, but this are my 0.02.

 

[Dirk]

When the IntelliChem controls the IntelliChlor it runs the SWG at 100% output until the ORP achieves set point. It doesn’t matter what you set the IC to in the EasyTouch panel, the IntelliChem is the big boss man.

Thanks for that reminder. I had forgotten that. The IntelliChem overrides any setting in the IntelliChlor, it just uses it as a dumb chlorine production plant. So it runs it at 100% and turns the output on and off like a light switch.

But that could still explain the short lifespan. If for whatever reason the IntelliChem is hammering the IntelliChlor 24/7, it'd only last a year and a few months. As I said, if it's not doing that constantly, and it only lasted a year or less, then you got a lemon. It happens.

Also, I disagree with Pentair and @Dirk regarding the acid injector but it’s what the manufacturer directs people to do and so it’s done. Acid is very bad for ruthenium coatings … doesn’t matter the concentration. Ruthenium hydrated complexes are very water soluble and they can form in oxidative environments at all pH levels below 10 or so (the lower the pH, the more thermodynamically stable they become) and chloride ions are really good at making them even more soluble (sulfates are even better at it). It’s why SWG anodes are consumable.

I can't argue the science. @JoyfulNoise, can you think of a reason that Pentair made this choice? Or make one up?! I've disassembled the Pentair acid injector. It's all plastic. There's a little ball floatie thing that seals up any backflow, so I can't imagine how the super-chlorinated water coming off the SWG would cause any issues for the injector should it be mounted after the SWG.

When I first installed mine after reading the instructions, I half-assumed the injector was first to give the SWG plates a periodic acid bath, to keep them nice and calcium free. But as you describe, that can't be it. Or it could be the reason, if the Pentair engineers didn't know any better about the acid and the ruthenium coatings, which is not inconceivable.

 

[JoyfulNoise]

I’d say more than one data point is needed. One cell was shot after one year, could have easily been a lemon out of the factory. As much as I like Pentair hardware, I don’t think their plates are any different than anyone else’s - they all come from the same few factories in Asia. Let’s see how long this new one lasts. If this pool owner keeps chewing through SWGs every years or so, then that would indicate a problem with the way the system is setup or the pool chemistry.

I had forgotten (or totally misread) that Pentair suggests using a 1:1 dilution of acid. That’s a much better approach to acid injection than full strength MA. Finding the sweet spot of acid dilution and tank filling frequency is a good idea - use the most dilute acid you can at the shortest fill cycle you’re willing to tolerate. And, as is always the case, an ounce of preventative maintenance on the tubes and check valve goes a long way to ensuring that the system doesn’t cause any inadvertent leaks.

 

[wireform]

One more fact I forgot to mention but can't remember the cause or what my argument was I had with the pb because I was checking on chems and there were some ridiculous swings. He wasn't a happy camper but he looked stupid and said he'll look into it. I said at the time something here ain't right. It turned out the intellichem controller was bad and changed it out under warranty too which corrected whatever it was that bothered me. For all you know the cell wasn't being shut off while the acid was acid injection happening.

 

[Flying Tivo]

Its funny looking back a my pool journey. Initially i would look for exact numbers and a perfect CSI. Now the whole range of numbers is fine with me and my pool. A simple timer/dosing system is more fool proof than any system out there. Dont know if one gets wiser with age, but do know i get older.

 

[JoyfulNoise]

I understand the urge to automate everything but, honestly, the law of diminishing returns is applicable. As one starts heaping on more and more automation, the problems, performance, maintenance issues start to grow faster than any perceived or actual benefit. Just like @Flying Tivo , if my pool water tests out in the right ranges, then I’m perfectly fine with that. The pool water is very stable these days and I can mostly ignore it between testing (which is probably less frequent than it should be ).