Heater bolts corroding

[JamesW]

If it was full of water, it would be leaking out.

Hard to tell for sure why the bolts corroded.

I would replace the bolts and periodically remove a bottom bolt to see if the heater is leaking.

Do not run the heater with any bolts missing.

 

[joepaiii]

If it was full of water, it would be leaking out.

Hard to tell for sure why the bolts corroded.

I would replace the bolts and periodically remove a bottom bolt to see if the heater is leaking.

Do not run the heater with any bolts missing.

Do you have the specs on the bolts? Thanks for all your help!

 

[JamesW]

I do not know the specs.

Take it to a fastener place and get good stainless steel bolts.

Replace one at a time.

 

[1poolman1]

Do you have the specs on the bolts? Thanks for all your help!

The leak is most likely at the mounting plate behind the manifold, not inside the combustion chamber or it would fill with water and eventually come out the blower, as JamesW mentioned.
The usual cause for those bolts to rust is the ends of the tubes have corroded away and water is not staying inside the manifold because, with the tubes shortened by corrosion, they are no longer inside the manifold and the O rings can no longer seal.
This is how the exchanger looked new:

Look at the video, at the 3:55 mark, to see what likely happened to your heater (I saw that kind of damage after 6-months for an improperly cared for pool):

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[JamesW]

Looks like you will need to remove the manifold to check the tube ends.

 

[joepaiii]

The leak is most likely at the mounting plate behind the manifold, not inside the combustion chamber or it would fill with water and eventually come out the blower, as JamesW mentioned.
The usual cause for those bolts to rust is the ends of the tubes have corroded away and water is not staying inside the manifold because, with the tubes shortened by corrosion, they are no longer inside the manifold and the O rings can no longer seal.
This is how the exchanger looked new:
View attachment 610828
Look at the video, at the 3:55 mark, to see what likely happened to your heater (I saw that kind of damage after 6-months for an improperly cared for pool):

Google Search

What type of chemical problems can cause it? My ph never gets really low. It may get a little high in the middle of winter but using the LSI calculations seem to suggest when water is cold that doesn't matter as much. I have been maintaining the pool and use all the tfp testing kits and try to keep it aligned with the tfp guidelines.

 

[1poolman1]

What type of chemical problems can cause it? My ph never gets really low. It may get a little high in the middle of winter but using the LSI calculations seem to suggest when water is cold that doesn't matter as much. I have been maintaining the pool and use all the tfp testing kits and try to keep it aligned with the tfp guidelines.

Couldn't begin to guess at that for your pool, especially from 1500 miles away.
It could also be water moving too fast. I'd check the usual RPM the system runs.
Its not the SWG, even if it was producing chlorine when the system is off (very difficult for that to happen), as its a gas that would rise, not fall into the heater, so don't worry about that. The amount it produces when running is quickly sent to the pool, so that is not an issue.
The proper amount of salt in a pool with a SWG is less than the amount in tears, so that is not the issue.
Pool water itself is very hard on everything and has to stay where it is intended. As you see, even stainless-steel bolts are not completely safe, though those bolts are not high-grade stainless because they shouldn't have to be.

 

[JamesW]

Do you have the specs on the bolts?

5/16x2-3/4” SS Hx Hd Capscrew.

Note: 5/16" can be course (18 TPI) or Fine (24 TPI), so measure the TPI (Threads per inch).



5/16x2-3/4” SS Hx Hd Capscrew

https://www.pentair.com/content/dam/extranet/nam/pentair-pool/residential/heaters/max-e-therm/manuals/maxetherm-heater-manifold-replacement-manual-english.pdf

The main difference between fine and coarse thread bolts is the pitch, or number of threads per inch (TPI):

• Fine thread
  A 5/16" fine thread bolt has 24 TPI. Fine threads are better for applications where vibration is a problem, or where precise adjustments are needed. They also provide more strength in shear and tension, and are better for thick gauge metal.
• Coarse thread
  A 5/16" coarse thread bolt has 18 TPI. Coarse threads are stronger than fine threads, and are better for most applications, including construction and industrial use. They are also better for thin gauge metal, and are often used in aviation and military applications.

 

[JamesW]

Looks like it is probably 5/16"-18 x 2-3/4" long.

I am pretty sure that the original screws are not stainless.

 

[JamesW]

https://www.pentair.com/content/dam/extranet/nam/pentair-pool/residential/parts-sheets/product-catalog-parts/pool-heaters-parts.pdf

 

[joepaiii]

I wonder if adding stabilizer to the skimmer did this. I don’t use a skimmer sock and thought it was ok since it gets to filter first. This was usually once a season in the spring to get cya up. But maybe that caused an issue.

I am beyond sad that this happened this quick as I thought I was doing things right with my chemistry.

My TA always runs between 50-70. It had run lower and then I pushed it up. The CH is usually 270-300. My FC is usually always between 2-8 depending on cya level. My cya is usually 20-30 after winter and then I get it to 50-60 for summer. My ph always shows 8 when I test and 1 drop of acids demand gets it to 7.4 color and I add 4 cups of acid near a return (20k gallons). I have waterfall so that and the SWG push ph up.

Anyway thanks for the help and I will post pics when I finally pull the manifold to see what the exchanger looks like. If I replace it I am thinking to put an automatic bypass in. Seems like a no brainer to help with heater life and get better flow at lower rpm’s with my pump.

Also wondering how much better the HD heat exchanger is. Also like to understand the ETI heater vs master temp.

 

[JamesW]

I wonder if adding stabilizer to the skimmer did this.

Probably not.

The pH does not drop that much downstream.

A lot of exposure would probably have an effect, but once or twice is probably not significant.

Maybe an electrical issue causing corrosion.

Do you have any other corrosion anywhere?

 

[joepaiii]

Probably not.

The pH does not drop that much downstream.

A lot of exposure would probably have an effect, but once or twice is probably not significant.

Maybe an electrical issue causing corrosion.

Do you have any other corrosion anywhere?

Just the metal in the filter. Not really bad but shows rust. I have to pop off the manifold at some point. Probably will install an auto bypass since my intellicenter should handle it.

 

[joepaiii]

Here are my full tests from today. Still trying to understand if chemistry caused my problem. I will update again when I pull the manifold.

 

[JamesW]

I do not see any obvious signs of a chemistry problem from the reported numbers.