Quote Originally Posted by cmcq View Post
The insides of my 5-6 year old Pentair MiniMax NT gas heater just rusted out.
This calls for a lot more investigation as to what exactly happened.

There should be nothing inside the heater to "rust" which means we are using the common name for iron or steel reacting to oxygen in the water which shows as the delightful orange stains we have all seen.

Since there should be no ferric substances in any pool piping; what could have rusted? As noted in a prior post, we may be dealing with a chicken and egg scenario whereas a leak somewhere attacked the shell of the heater which caused the rust you are seeing.

Since no units are perfect and since no light commercial pipe is truly tested for proper thickness with these units, a leak in a copper coil may have developed due to improper bending and/or annealing of said pipes or from using a lighter gauge pipe like type m where type L or thicker should have been used. As I said, this pipe is used to create the coil"s" that the pool water circulates through.

I have seen this happen with coils on heat pumps that carried r-22 refrigerant which is not close to being as corrosive as pool water. It was simply a bad batch of pipe that Trane bought to make their coils. The coils were replaced by Trane less the labour to replaced said coils and with that, this is why I would investigate where the leak originates.

Why all the bother?

If it is a small section of a coil it can be replaced for a nominal fee and you again have a working heater for little cost.

If an Iron pipe nipple was used where a brass nipple should have been used, same procedure; replace the nipple with a brass nipple and off you go.

Lastly, you may have recourse with Pentair to at least get a replacement coil.

So out with the tools and please let us know what you find inside the unit.