On my second heat exchanger!

[Rngr275]

Evening all… It has been awhile.
So I installed a Takagi T-K4-IN-P around September 2012. It developed a water leak up in the combustion chamber December 2013 (15 months old). The heating coils and chamber were in perfect shape and they replaced the exchanger, no questions asked. Two weeks ago there was no hot water and I found a puddle of water on the floor under the heater. Upon inspection I found that there was a pin hole leak in one of the elbow on the out side of the combustion chamber. It is not an elbow fitting but where the pipe is bent as it comes out of the heat exchanger (it does this multiple times in order to redirect the water in and out of the heat exchanger). The exchanger was only 9 months old. They want this one back to try and determine why it failed so quickly but from their questions they are looking to blame the water being supplied.
I recently tested the water which comes from a spring fed 500 gallon cistern in my basement (bought an Amish house). Everything looked great from the test (home test). Total Alkalinity~120, Chlorine~0, Total Hardness~0-50. The only thing that looked "Not Ideal" was the pH which was between 5 and 6.5 . I tested the pH with some other test strips from work which are a little more accurate and it was ~6. I know this is a little low.
My question(s) is/are:
Is a pH of 6 low enough to eat through a copper pipe in 9 months?
Do I need to treat water with a pH of 6.
Any other ideas on why the pipes keep forming leaks. Takagi was/is highly rated but it could be a quality issue on their side.
Thoughts?

Thanks McD

 

[Reach4]

See http://takagi.com/media/16158/2013_Warranty-info.pdf

See 5. THIS WARRANTY WILL NOT COVER THE FOLLOWING:• Introduction of water with pH levels less than 6.5 and greater than 8.5 into the product.

Also look at all of the other restrictions. This may not have been a good fit for you.

 

[Sponsor]

 

[Rngr275]

See http://takagi.com/media/16158/2013_Warranty-info.pdf

See 5. THIS WARRANTY WILL NOT COVER THE FOLLOWING:• Introduction of water with pH levels less than 6.5 and greater than 8.5 into the product.

Also look at all of the other restrictions. This may not have been a good fit for you.

Awfully tight pH spec. but it is what it is. SInce my pH is between 6-6.5 it appears I will need to treat the water. I think a Calcite filter system should work since the starting pH is not too low. I still find it hard to believe that water with a pH in the 6-6.5 range can eat through a copper pipe in 9 months.
Do any of you have recommendation for a good low cost calcite system?

Thanks
McD

 

[Reach4]

Don't forget the hardness requirements, which seem even more tight to me.

The calcite will raise the hardness, but I don't know by how much. Get a hardness test kit. The Hach 5-B is well respected.

"Hardness~0-50" ... is that a test strip range in PPM? There are about 17.1 PPM per grain.

 

[Rngr275]

Don't forget the hardness requirements, which seem even more tight to me.

The calcite will raise the hardness, but I don't know by how much. Get a hardness test kit. The Hach 5-B is well respected.

"Hardness~0-50" ... is that a test strip range in PPM? There are about 17.1 PPM per grain.

The hardness was tested at 50ppm (or less). Takagi's spec for hardness is 120ppm so I have a little room. Thanks for your input.