Mastertemp 300 heat exchanger leaking/went out

[Rle015001]

My 3 1/2 year old Pentair Mastertemp 300 natural gas heat exchanger is leaking and causes a loud noise and then shuts off. Apparently my chlorine got too high and caused the copper pipe to corrode and spit blue/black particles in my spillover hot tub during the winter. 20K gallon total that includes pool and spillover hot tub. I was told by my pool installer that I can either replace the exchanger for $2600 ($1800 for the parts and $800 for labor) or I can purchase a new Mastertemp 250 for $4300 ($3730 new unit and $600 to install).
1)Thoughts on what I should do keeping in mind the new one is 50K BTU less than the one I have. Also, I don’t know if there is any other damage to the heater.
2) Are these prices reasonable?
3) Where is the best place to buy a new heater?

 

[JoyfulNoise]

Chlorine “getting too high” doesn’t cause a heat exchanger to fail. Heat exchanger failures are either due to poor water chemistry (low pH) or mechanical erosion caused by excessive water flow. Also, running the heater outside of the recommended water and air temperature ranges can cause soot damage and/or condensate damage to the heat exchanger.

Did the technician show you the damage they found?

How has this pool been cared for? What type of chlorine sources are being used?

Is the plumbing correctly installed?

Heat exchangers can and do fail but there’s usually a certain cause for it other than a general statement about “too much chlorine”. If you don’t find the root cause of the failure then you risk wrecking a new heater.

Can’t say much about pricing as it varies from area to area. Only way to know for sure is to get multiple quotes. Typically it’s not worth paying for a heat exchanger replacement as it’s a lot of work and there’s very little warranty offered. If they replace it and it fails again in 6 months, you’ll be back to square one. Usually it makes more sense to install a new heater. The lower BTUs just means that it will take longer to heat things but you’ll still use the same amount of gas no matter what.

 

[JamesW]

Black and coral specs in hot tub (possibly from heater)

I used my wave blaster to clean my in ground hot tub and I have the following sitting on the seat and bottom. Pool is shut off in winter and we keep the hot tub open. I presume it has something to do with unbalanced chemicals eating at the copper tubing in my heater. Can anyone tell me what...

www.troublefreepool.com

You need to figure out what happened early on to destroy the heater.

What details are available?

Can you show pictures of everything?

 

[JamesW]

Be ready to bypass it when it starts to leak.

 

[Rle015001]

Chlorine “getting too high” doesn’t cause a heat exchanger to fail. Heat exchanger failures are either due to poor water chemistry (low pH) or mechanical erosion caused by excessive water flow. Also, running the heater outside of the recommended water and air temperature ranges can cause soot damage and/or condensate damage to the heat exchanger.

Did the technician show you the damage they found?

How has this pool been cared for? What type of chlorine sources are being used?

Is the plumbing correctly installed?

Heat exchangers can and do fail but there’s usually a certain cause for it other than a general statement about “too much chlorine”. If you don’t find the root cause of the failure then you risk wrecking a new heater.

Can’t say much about pricing as it varies from area to area. Only way to know for sure is to get multiple quotes. Typically it’s not worth paying for a heat exchanger replacement as it’s a lot of work and there’s very little warranty offered. If they replace it and it fails again in 6 months, you’ll be back to square one. Usually it makes more sense to install a new heater. The lower BTUs just means that it will take longer to heat things but you’ll still use the same amount of gas no matter what.

Apologies. Let me correct my statement. Unbalanced chemicals I believe is what I was told. I do remember two winters ago the chemicals got out of whack for 2-3 weeks. Attached is a pic technician provided me.

 

[Rle015001]

Apologies. Let me correct my statement. Unbalanced chemicals I believe is what I was told. I do remember two winters ago the chemicals got out of whack for 2-3 weeks. Attached is a pic technician provided me.
View attachment 481242

Here is a pic of my wave blaster cleaning the hot tub. Notice the blue and black particles.

 

[JamesW]

I would get a new heater, but make sure that everything is 100% perfect on the install and the operation.

 

[JoyfulNoise]

It seems odd to me that chemistry could do that unless your pool water was wildly acidic, like a pH below 5, for months on end or, perhaps, there was tablet feeder running without a check valve or the check valve failed.

There’s no point in spending thousands of dollars on a new heater if the same conditions are going to exist to wreck the new heater. Outside of a manufacturing defect, a pool heater should easily last 10 years or more with good use and proper maintenance.

 

[JamesW]

I do remember two winters ago the chemicals got out of whack for 2-3 weeks.

Can you explain this better?

 

[JoyfulNoise]

I guess the point is - if you can’t figure out why this happened, not just what happened, then you risk the same damage all over again.

The black colored scale with blue flakes in it is very odd. That would indicate a scale forming inside the copper tubing as anything built up on the outside of the heater would not get pulled in through a leak as this is the pressure side of the plumbing. So this points to improper water chemistry management.

Can you describe how this pool is cared for? What chemicals are added to it on a regular basis? How is it treated in the off season?

 

[ajw22]

I doubt your heater was killed by bad water chemistry unless you used Trichlor tablets in a feeder.

I suspect corrosive condensation from cold weather operation did it.

Heater Condensation - Further Reading

www.troublefreepool.com

My prediction is if you install another MasterTemp heater and run it the same way it too will leak in about 4 years.

 

[Rle015001]

Can you explain this better?

The 2nd winter we had the pool, for some reason the chlorinator settings were off. We had no issues the first winter but the second one (and ever since) we have to toggle the settings on the chlorinator between 1% and 0% because if we leave it at 1% the chlorine will be off the charts. That 2nd winter we went to check the chemicals in the spa and the chlorine was extremely high, ph was low and all the numbers were off but I don’t remember what they were.

 

[ajw22]

The 2nd winter we had the pool, for some reason the chlorinator settings were off.

What type of chlorinator are we discussing?

What is the calcium hardness (CH) level in your pool?

 

[1poolman1]

It seems odd to me that chemistry could do that unless your pool water was wildly acidic, like a pH below 5, for months on end or, perhaps, there was tablet feeder running without a check valve or the check valve failed.

There’s no point in spending thousands of dollars on a new heater if the same conditions are going to exist to wreck the new heater. Outside of a manufacturing defect, a pool heater should easily last 10 years or more with good use and proper maintenance.

You can see that type of damage very often in pools like the OP (vinyl liner) and fiberglass when the pH and alkalinity get crazy low. If tablets are used its even worse. Unless tablets are used exclusively, I've never seen that in a plaster pool. The water will go after anything it can to become alkaline. In a plaster pool that's the plaster if it isn't adjusted properly. Vinyl and fiberglass don't have a source the water can attack other than the equipment, especially the soft copper in a heat exchanger (and any other metals, like the spring on a shaft seal). That's why I remove tab feeders when I do a heater install.

Just before COVID (that's how we measure things now) I did an install of a Max-E-Therm for another company. They had a tab feeder in line that they allowed me to remove as I wouldn't do the install with it still in place. Six months later got a call that the heater was leaking. It wasn't leaking, water was being pumped out the combustion blower. The "service tech" (I use that phrase instead of what I would like to call him) re-installed the tab feeder, which alone shouldn't have caused the issue in six months. But, when I went to test the pool I found it to be fiberglass with zero alkalinity and pH so low it couldn't really be measured with my Taylor test kit. No, I hadn't seen the pool. It was much farther in the backyard, around a corner, and I don't need to see the pool to install a heater.

 

[ajw22]

But, when I went to test the pool I found it to be fiberglass with zero alkalinity and pH so low it couldn't really be measured with my Taylor test kit.

Fiberglass pools with gas heaters should have at least 200 ppm of calcium.

Direct fired gas heaters tend to build up a thin layer of calcium carbonate on their internal surfaces over time. This thin layer acts as a barrier to physical metal erosion (from high flow rates of water) and chemical attack (from chlorine). However, this film is not indestructible and it can come and go over time depending on CH and pH levels.

Trichlor contains acid that lowers the pH and chlorine. It's the combination of low pH and chlorine that is most corrosive.

Low pH prevents or removes the formation of a protective layer of calcium on the heat exchanger and chlorine oxidizes the copper. This is why maintaining a Calcium Hardness of at least 200 ppm is recommended if you have a gas heater.

It is often said it is the low pH caused by the acid in Trichlor that damages the heat exchanger. Of the four industrially important strong acids, only two, nitric and sulfuric, are strong enough oxidizing agents to dissolve copper. The concentration of copper(II) ions is larger with the nitric acid, because it is a stronger oxidizing agent than sulfuric acid.

Copper in Concentrated Strong Acids

 

[1poolman1]

Fiberglass pools with gas heaters should have at least 200 ppm of calcium.

Direct fired gas heaters tend to build up a thin layer of calcium carbonate on their internal surfaces over time. This thin layer acts as a barrier to physical metal erosion (from high flow rates of water) and chemical attack (from chlorine). However, this film is not indestructible and it can come and go over time depending on CH and pH levels.

Trichlor contains acid that lowers the pH and chlorine. It's the combination of low pH and chlorine that is most corrosive.

Low pH prevents or removes the formation of a protective layer of calcium on the heat exchanger and chlorine oxidizes the copper. This is why maintaining a Calcium Hardness of at least 200 ppm is recommended if you have a gas heater.

It is often said it is the low pH caused by the acid in Trichlor that damages the heat exchanger. Of the four industrially important strong acids, only two, nitric and sulfuric, are strong enough oxidizing agents to dissolve copper. The concentration of copper(II) ions is larger with the nitric acid, because it is a stronger oxidizing agent than sulfuric acid.

Copper in Concentrated Strong Acids

You know chemistry, I only know what I've experienced. Chemistry was the one subject I couldn't ever get straight.
Either way, vinyl or fiberglass pools with tablets are a recipe for disaster when it comes to pool heaters if the pH, alkalinity, and CH aren't cared for properly. I freely admit that I've made a good living because someone wouldn't care for their water correctly, even though I do all I can to educate.

 

[JamesW]

If you put a metal like aluminum, zinc or magnesium in hydrochloric acid, the hydrogen ions will oxidize the metal and cause it to dissolve.

The hydrogen ions will be reduced to hydrogen gas.

However, hydrogen ions will not oxidize copper.

When copper is oxidized by oxygen, the copper forms a layer of copper oxide.

Because the copper in copper oxide is oxidized, this creates a protective barrier that prevents further oxidation because the oxygen cannot get past the copper oxide to the underlying copper metal.

This is why old copper pennies usually get a uniform chocolate brown color.

If you put the copper in a low pH solution, the copper oxide layer can be stripped off and then oxygen or other oxidizers like chlorine can attack the metal.

So, in a pool with low pH, the copper will be destroyed because the protective layer will not be able to form and oxygen and chlorine will continue to oxidize and dissolve the copper.

Notice in the below video they had to add hydrogen peroxide in addition to acid to make the copper dissolve.

 

[JamesW]

In this picture, you can see that the copper in solution is shiny metal and above the solution is brown due to the copper oxide layer.

The acid strips off the copper oxide and then the H2O2 can begin to oxidize the copper metal.

 

[JamesW]

The reactivity of six metals are qualitatively tested by adding 3M HCl.

If the metal reacts with HCl it will react with H+ from the dissociation of HCl and make Hydrogen gas (bubbles) and the metal chloride.

The spontaneity of the reaction will be done by observing the production of hydrogen gas.

 

[Rle015001]

What type of chlorinator are we discussing?

What is the calcium hardness (CH) level in your pool?

Intellichlor IC 40

Pool is still hovered so I cannot rest the calcium hardness. I do have another question in that should I be using something other than test strips or possibly take a water sample to Leslie Pool up the street for testing?