Total Alkalinity and Pentair Pool Heater

[JamesW]

I am talking about the chlorine from the tab juice.

Tab juice is liquid with trichlor dissolved at maximum solubility.

The juice has a very low pH and a super high level of chlorine including chlorine gas.

The low pH strips off the protective copper oxide coating and the chlorine viciously and violently rips the electrons from the copper.

 

[dustindclark]

I just have a hard time believing that it's a tab feeder issue given 1) how rarely I used tabs, 2) the fact that the system (including the check valve) is only 21 months old, and 3) that the 3-way valve always routed water through the heater (never bypassed, so in this configuration, there's no way for tabs to flow to the heater).

I would estimate that 90% of the time I used liquid bleach. The 10% of the time was when I was leaving town for more than a week and some rare occasions where I didn't have bleach available. It was very infrequent...I still have some of the second box of tabs left.

Looking back through my logs, the lowest my pH has been is 7.2, and the only reason it was that low was that I was working to decrease TA per the TFP app:

To lower TA you reduce pH to 7.0-7.2 with acid and then aerate to increase pH

That guidance would seem to void the Pentair warranty since the minimum is 7.2 per the manual.

I get that all signs point to a chemistry issue, but I don't see how this recipe adds up to a heater failure in 21 months.

 

[proavia]

I thought chlorine was not an issue? Isn’t it usually due to low ph/acid? Or can high chlorine contribute?

And if the answer is that high chlorine can contribute to this heater issue, does that mean slams are dangerous to equipment?

Tabs are acidic.
With no flow, the chlorine levels rise and and pH drops (acidic).
That's what causes the damage.
SLAM chlorine levels are not an issue.

 

[JamesW]

In my opinion, the liquid from the tab feeder got into the heater.

Low pH by itself won't dissolve copper.

When the copper is new, the oxidizers in the water will oxidize the copper and a film of copper oxide will form a coating on the copper and this creates a barrier to further oxidation.

However, if the pH is too low, the protective layer will not form or it will be removed, which exposes the copper to more oxidation from chlorine and oxygen in the water.

It seems obvious to me that the liquid from the tab feeder got into the heater and caused the damage.

It is also possible that the bypass was set incorrectly, which will cause the heater to run with no flow.

Can you remove the heat exchanger and show what it looks like?

 

[JoyfulNoise]

The diverter valve highlighted in red is your problem -



These valves are NOT chemically resistant (not that it matters) nor do they create a perfect seal. When the pump stops running, the acidic "tab juice" in the tablet feeder WILL back flow into the plumbing. It will acidify the water all the way behind it. That includes the check valve (which in and of itself does not create a perfect seal) AND the diverter.

While I understand your disbelief, let me assure you that it is entirely chemically possible. It doesn't take much acid to completely remove all the carbonate alkalinity in water and turn the water very acidic. Trichlor can easily drop the pH of water down to 4.5 (the point of zero alkalinity). Once the pH of water drops below 7.0, copper oxide is no longer stable and breaks down leaving bare copper metal as the most stable chemical species.

As @JamesW alluded to, copper metal by itself will not dissolve in low pH .. but, copper metal in the presence of high chloride ion (Cl-) concentration AND low pH will start to dissolve rapidly. That is exactly what the "tab juice" is - low pH, high oxidizer levels (in the form of chlorine), and high chloride (spent chlorine) concentration. Any amount of trichlor used can cause this damaging effect and then, once enough copper is removed, the heater is toast.

Get rid of the tab feeder, it is not your friend. Switch over the an SWG and you will never have this problem because SWG's do not produce acidic by-products.

 

[JamesW]

If the diverter valve was rotated 180 degrees, the liquid from the tabs could go into the inlet of the heater.

All it takes is one time.

Also, that orientation will cause the heater pressure switch to close and the heater can fire with no flow.

Sorry to say, but it looks like user error and not a warranty issue.

 

[dustindclark]

If the diverter valve was rotated 180 degrees, the liquid from the tabs could go into the inlet of the heater.

All it takes is one time.

Also, that orientation will cause the heater pressure switch to close and the heater can fire with no flow.

What I'm saying is that that diverter valve was never touched until after the heater failed...water always flowed through the heater until the heater started leaking. That was the first time in 21 months that I had bypassed the heater. If the diverter valve can also leak, then that is news to me. Neither the diverter valve nor the check valve are leaking now though with the heater disconnected.

Sorry to say, but it looks like user error and not a warranty issue.

If by "user error", you mean occasionally using tabs, then yes...I guess I'm guilty. I didn't plumb the system myself though, so I'd say I've been using the system as designed/built.

While I understand your disbelief, let me assure you that it is entirely chemically possible. It doesn't take much acid to completely remove all the carbonate alkalinity in water and turn the water very acidic. Trichlor can easily drop the pH of water down to 4.5 (the point of zero alkalinity). Once the pH of water drops below 7.0, copper oxide is no longer stable and breaks down leaving bare copper metal as the most stable chemical species.

Don't get me wrong...I believe you and I appreciate the analysis. I just don't understand why installers put them in and why tabs are so common if they eat heaters...especially with limited use.

 

[JamesW]

The 10% of the time was when I was leaving town for more than a week and some rare occasions where I didn't have bleach available.

Maybe while you were out of town, someone was playing around with the valve?

 

[kul]

All it takes is one time.

I had no idea it was this destructive! Thanks for the information!

 

[dustindclark]

Maybe while you were out of town, someone was playing around with the valve?

It's possible but unlikely. Cover stays closed and my wife doesn't generally even let the kids swim while I'm not home. Kids say they've never touched it, but you know how that goes. I've definitely never come home and found it changed.

The pump runs from 7AM to 2:30PM every day...definitely doesn't run nonstop. I've turned the pump on/off and opened/closed the automated valves trying to recreate, and I can't get a drop out of the check valve or the diverter with the heater disconnected. I'm sure they're not 100%..just saying that I can't deliberately make them leak.

 

[JoyfulNoise]

Tab feeders were never meant for residential pools. I believe their history comes from use on commercial pools where pumps run 24/7. But once commercial pool regulations started limiting the amount of cyanuric acid in pool water, commercial use dried up. So the manufacturers repurposed the product for the residential space. The problem is, they create a toxic stew of chemicals inside of them that doesn’t take long to destroy everything around them. A simple check valve or diverted really isn’t enough to hold back the diffusion of chemicals throughout the water. They won’t leak in a gross sense of the word but they are not chemically sealed.

I don’t think anyone is blaming you but you’ve gotten the wrong advice especially from the technician and Pentair. They want to think that a tiny excursion in TA is what caused all the problems. But that’s not it. It’s their tab feeder and the way your pool was designed and programmed to run. That is what led to the chemical exposure and damage. But, the way their warranty is written and the way the industry is, it’s your fault, case-closed.

Sadly the fix involved buying a new heater and ripping out that tab chlorinator. If you want to use tabs, then fine, use them. But you can only do so in a chemical tablet floater in the pool, not using a automatic feeder in the plumbing.

 

[Rancho Cost-a-Lotta]

Pentair recommends the Rainbow corrosion resistant check valve for installations with heaters (as mentioned by @1poolman1). I'm guessing this will be more justification for Pentair to deny the warranty claim. From the manual:

If your pool or spa has any of the following equipment, special plumbing procedures must be followed for safe operation:

1. Brass or bronze gate, rotary or backwash valves.
2. The preceding valves constructed of PVC or other plastic material with metallic shafts.
3. Filters, heaters, heat exchanges or other items with metallic tanks, shafts, coils or tubes.
4. NOT FOR USE IN COPPER PLUMBING.

Installation of the OPTIONAL Rainbow #R172288 positive seal, corrosion resistant check valve SHOWN ON REVERSE SIDE will prevent the backflow of corrosive liquids and gases that can damage equipment containing metallic components. Examples listed above.

Pentair Rainbow Corrosion Resistant PVC Check Valve 1.5" x 2" | R172288

Pool Supply Unlimited has some of the best prices when shopping for Pentair Rainbow Corrosion Resistant PVC Check Valve 1.5" x 2" | R172288

www.poolsupplyunlimited.com

I hope you're able to get the issue resolved with Pentair and the builder.

Best wishes!

 

[JamesW]

Copper does not react with the hydrogen ions in acid due to being less reactive than hydrogen.

For metals that are more reactive than hydrogen, the hydrogen oxidizes the metal and the hydrogen becomes hydrogen gas.

You can see in the videos that copper has no reaction, but zinc and magnesium have a strong reaction and the bubbles are hydrogen gas.

The metal goes from being in the elemental form to the ionic form.

The below video shows that an oxidizer like hydrogen peroxide, chlorine, bromine or oxygen is needed to oxidize the copper.

The acid just keeps any oxidized copper ions from forming a protective layer on the copper.

If you look at an old penny, you will see that it has turned brown due to the layer of copper oxide and other copper compounds and the elemental copper is not exposed to the oxygen in the air.

However, if you drop the penny in acid, the brown layer will be removed and the elemental copper will be exposed and vulnerable to oxidation.

 

[dustindclark]

Pentair recommends the Rainbow corrosion resistant check valve for installations with heaters (as mentioned by @1poolman1). I'm guessing this will be more justification for Pentair to deny the warranty claim. From the manual:

If your pool or spa has any of the following equipment, special plumbing procedures must be followed for safe operation:

1. Brass or bronze gate, rotary or backwash valves.
2. The preceding valves constructed of PVC or other plastic material with metallic shafts.
3. Filters, heaters, heat exchanges or other items with metallic tanks, shafts, coils or tubes.
4. NOT FOR USE IN COPPER PLUMBING.

Installation of the OPTIONAL Rainbow #R172288 positive seal, corrosion resistant check valve SHOWN ON REVERSE SIDE will prevent the backflow of corrosive liquids and gases that can damage equipment containing metallic components. Examples listed above.

Pentair Rainbow Corrosion Resistant PVC Check Valve 1.5" x 2" | R172288

Pool Supply Unlimited has some of the best prices when shopping for Pentair Rainbow Corrosion Resistant PVC Check Valve 1.5" x 2" | R172288

www.poolsupplyunlimited.com

I hope you're able to get the issue resolved with Pentair and the builder.

Best wishes!

This is the check valve I have.

 

[1poolman1]

I just have a hard time believing that it's a tab feeder issue given 1) how rarely I used tabs, 2) the fact that the system (including the check valve) is only 21 months old, and 3) that the 3-way valve always routed water through the heater (never bypassed, so in this configuration, there's no way for tabs to flow to the heater).

I would estimate that 90% of the time I used liquid bleach. The 10% of the time was when I was leaving town for more than a week and some rare occasions where I didn't have bleach available. It was very infrequent...I still have some of the second box of tabs left.

Looking back through my logs, the lowest my pH has been is 7.2, and the only reason it was that low was that I was working to decrease TA per the TFP app:



That guidance would seem to void the Pentair warranty since the minimum is 7.2 per the manual.

I get that all signs point to a chemistry issue, but I don't see how this recipe adds up to a heater failure in 21 months.

For example, I installed a heater for another company in December of 2021. It was a Max-E-Therm, same heater as yours in a different housing. Pool had the same inline tablet feeder as yours. I refuse to install the heater without removing that and the homeowner gave permission.

Six or seven months later the other company called and said the heater was leaking. Upon inspection I found three things; first the tab feeder had been reinstalled by the service company. Second the alkalinity was about 50. Third, water was being pumped out of the blower as the heat exchanger was completely destroyed. Pictures of the heat exchanger, like the picture you posted, showed the ends of the tubes almost gone.
No, Pentair would not warranty the heater, as they shouldn't, because of user error.

Have seen the same thing in other heaters, RayPak and Hayward, that I installed and the service company installed one of those terribly-destructive feeders. The RayPak, fortunately, only had an issue in the manifold, but had the temp sensor and the uni-therm governor (same as the thermal regulator in your heater) destroyed in less that two months.

The Hayward had the same issue as yours, a badly damaged heat exchanger in about nine months.

Twenty-one months, sadly, is well within time for that damage to occur. The heat exchanger can be replaced for less than the cost of the entire heater, but it is a very large job. Usually the cost is about 50% of the cost of a new heater for a company to do it.

 

[kul]

This all makes a lot of sense. My heater is about 7 years old and the heat exchanger just went out and is leaking. While I have cared for my pool the last almost 2 years, it was serviced by a pool guy and pool store suggestions in the past. Pucks were routinely in the skimmer basket and the pool guy said the previous owner used to like adding a lot of acid. I’m guessing that’s why I didn’t make it to 10 years. Things happen. Live and learn. Hopefully the next one lasts longer since I use the TFP guidance.

 

[1poolman1]

This all makes a lot of sense. My heater is about 7 years old and the heat exchanger just went out and is leaking. While I have cared for my pool the last almost 2 years, it was serviced by a pool guy and pool store suggestions in the past. Pucks were routinely in the skimmer basket and the pool guy said the previous owner used to like adding a lot of acid. I’m guessing that’s why I didn’t make it to 10 years. Things happen. Live and learn. Hopefully the next one lasts longer since I use the TFP guidance.

Because they have been marketed for decades as "skimmer tablets," there are two groups of people who love pool owners to put tablets in the skimmer, those who replace skimmers (yes the tablets do damage the plastics) and those who repair/replace pumps and heaters.

 

[dustindclark]

Twenty-one months, sadly, is well within time for that damage to occur. The heat exchanger can be replaced for less than the cost of the entire heater, but it is a very large job. Usually the cost is about 50% of the cost of a new heater for a company to do it.

This is an interesting option, especially if I could do this myself. It looks like the exchanger kit is $2,062 though if I'm reading this right (page 451 here). Since my original heater was $2,552 (still working on a quote for a new one), it doesn't seem worth the hassle.

 

[Ahultin]

This is an interesting option, especially if I could do this myself. It looks like the exchanger kit is $2,062 though if I'm reading this right (page 451 here). Since my original heater was $2,552 (still working on a quote for a new one), it doesn't seem worth the hassle.

Heat exchanger can be found online for half of the shown "list price"

 

[JoyfulNoise]

This is an interesting option, especially if I could do this myself. It looks like the exchanger kit is $2,062 though if I'm reading this right (page 451 here). Since my original heater was $2,552 (still working on a quote for a new one), it doesn't seem worth the hassle.

It's A LOT of work. It's doable on your own but you should plan for spending at least an entire day on it assuming everything unbolts correctly and nothing breaks in the process. @PoolGate rebuilt his heater when his heat exchanger failed (it was a Jandy) so he can give some insight into the DIY difficulty level.