Total Alkalinity and Pentair Pool Heater

[dustindclark]

I have a Pentair MasterTemp 400K BTU Heater that is under warranty (pool startup was Thanksgiving 2021...so ~21 months ago). It recently started leaking, and the technician came out yesterday and confirmed that it is totaled. He pulled off the heater manifold, and the copper tubing had corroded through. He also tested the water, which showed high in copper and an alkalinity level of 50 (I tested when he left and my TFP kit shows between 60 and 70). In general. I have always targeted TA between 60 and 80 (per the TFP app) and a pH of 7.6. The alkalinity level is usually on the money (70ish), and pH (if anything) gets a little high...but it's mostly stable, so I rarely have to add muriatic acid.

I have not heard anything official from Pentair yet, but the tech says that they will likely deny the claim. He says that the ideal alkalinity is 80-100, and low alkalinity would be the reason that my heater failed. Prior to the discussion with the tech, my understanding was that low pH (not low alkalinity) would eat through metal components. Either way though, my pool chemistry has always stayed pretty close to the TFP recommendations. Per page 60 of the Pentair manual, the ideal pH is 7.4 to 7.6. I have definitely stayed in that range or higher. The ideal alkalinity range shows 80-100, but it shows a minimum of 60.

So, I guess my questions are:

1. Anyone had experience with Pentair in this regard? I guess it's my word against theirs on the chemistry...can I fight this with logs?
2. What TA should I really be targeting? 80-100?
3. Can low TA really cause copper to deteriorate and fail? No, right? Should be low pH. Either way, I really wish I had followed the Pentair recommendations rather than TFP...at least until my warranty had expired.
4. Why would there be a discrepancy between the tech's TA test and my TFP TA test?
5. Copper in the water seems bad...do I need to drain/refill?

 

[dustindclark]

Attaching pictures and test results from technician.

 

[JoyfulNoise]

Is there a trichlor tablet feeder on your plumbing or has anyone been putting trichlor tablets in the skimmer?

 

[dustindclark]

I'm the only one maintaining the pool. Yes, there's a tablet feeder (with a check valve behind it), but I rarely use it. I've used about 50 lbs of the tablets total since startup, and otherwise use liquid bleach.

 

[Bperry]

Attaching pictures and test results from technician.

I only see one copper tube corroded? Seems if there was a chemistry issue that all the tubes would have similar corrosion.

 

[dustindclark]

I only see one copper tube corroded? Seems if there was a chemistry issue that all the tubes would have similar corrosion.

This seems logical to me. Hopefully Pentair sees it the same way...

 

[dustindclark]

Pentair did not see it that way. They have indicated that this will not be covered under warranty.

 

[JamesW]

Can you show the system?

 

[dustindclark]

Can you show the system?

These are the best pictures I have with me (taken at install). Will try to get some better ones when I get home.

 

[pjt]

Why would there be a discrepancy between the tech's TA test and my TFP TA test?

The tech got the water tested at Leslie's. Their testing is lousy, and the "total alkalinity" listed is most likely adjusted alkalinity.

 

[pjt]

Yes, there's a tablet feeder (with a check valve behind it), but I rarely use it.

Can you verify the check valve is intact and functioning correctly?

 

[Bperry]

Pentair did not see it that way. They have indicated that this will not be covered under warranty.

Just kinda solidifies my belief that the warranty for this stuff is worthless. Was there reason that the TA was 10ppm too low? That’s pretty shady. Do you have logs of test results?

 

[JamesW]

Probably due to the tab feeder.

If the bypass is open, tab liquid can get into the heater.

The check valve is in the wrong place.

 

[dustindclark]

Just kinda solidifies my belief that the warranty for this stuff is worthless. Was there reason that the TA was 10ppm too low? That’s pretty shady. Do you have logs of test results?

Agree that it seems shady. Especially considering that I did the TFP TA test as he was leaving. In my test, it started to change color at 6 drops, but it didn't fully change until the 7th drop...so I think it's closer to 70. I'm not sure if that would matter though even if my numbers were perfect. It's my word against theirs as to the history of the chemicals.

Can you verify the check valve is intact and functioning correctly?

Yes. I had visually checked before he took it apart, but he left the heater disconnected....so if the check valve wasn't working, my system would be leaking with the heater bypassed (which isn't happening).

The tech got the water tested at Leslie's. Their testing is lousy, and the "total alkalinity" listed is most likely adjusted alkalinity.

Good eye...I totally missed that in the photo.

Probably due to the tab feeder.

If the bypass is open, tab liquid can get into the heater.

The check valve is in the wrong place.

The check valve is in the right place. The heater is bypassed and disconnected now, and the check valve isn't leaking. If it was in the wrong place or not working, I'd be leaking water when the system is on.

Also, until my heater started leaking, I never bypassed it (right or wrong)...so when the system was on, water was always flowing through the filter > heater > check valve > tablet feeder.... and thus never had pressure against the check valve. The copper pipe that failed was second from the top, so I think I'd have to have pressure going the wrong way for this to happen if it is a tablet feeder issue.

 

[1poolman1]

I only see one copper tube corroded? Seems if there was a chemistry issue that all the tubes would have similar corrosion.

Water pouring out of the lower bolt holes is the indication that the heat exchanger is gone. Its not the bad tube on the outside that is the problem. Appearance of the tubes isn't that bad, except that 21 months is a bit too soon.

Regardless of having a check valve before the tab feeder, the corrosive solution will get back into the heater as it deteriorates the seal in any check valve, including the so-called "chemical resistant" ones that Rainbow (now Pentair) made for that purpose.

Unfortunately, the damage that is seen is always the result of bad chemistry, unless there was some outrageously high flow rate through the heater. Even the rust on the mounting flange, which is stainless steel, is an indication of bad chemistry. Either way, it is never covered under warranty by any heater manufacturer.

 

[JoyfulNoise]

My heater has been exposed to pool water with a TA between 50 and 70ppm, pH anywhere in the 7’s (mostly stays around 7.6 or higher) and a CH above 500ppm for over ten years now. No corrosion issues whatsoever.

In my estimation, the root cause of the corrosion is that tab feeder. It may have “only” had 50lbs of tablets run through it (which is still quite a lot) but that could have been enough to strip off any protective layer that was there leaving bare copper to the mercy of pool water. Those tablet feeders are called “heater-eaters” for a reason. The initial burst of acidic chlorinated water probably kicked off the corrosion that slowly destroyed it over the last 22 months.

Sorry, it sucks. But that’s why TFP tells people all the time to get rid of those things … they are more trouble than they’re worth.

 

[JamesW]

If the bypass valve is set incorrectly, tab juice can go into the inlet of the heater and into the filter.

The angry red color of the copper is due to chlorine and low pH.

The rust on the stainless steel is also a good indication of chemical attack.

In my opinion, this is not a warranty issue.

Tab feeder juice is about as bad as it gets for copper and anything else.

It is nasty toxic dangerous and corrosive.

 

[proavia]

While this seems not to be a heater manufacturer issue, it might be a pool builder (or check valve installer) issue.

 

[JamesW]

The check valve is in the right place.

The check valve is not correct; it needs to be before the feeder with no way to get back to the system.

In any case, if you have tabs in the feeder, the pump needs to be on.

The second that the pump is off, the tab juice begins to get very dangerous, toxic and corrosive and it migrates through the system destroying everything in its path.

 

[kul]

angry red color of the copper is due to chlorine

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?