Cast, stainless, or bronze pump for Garn non-pressurized system.

[Sawyer]

I was looking for Grundfos 15-58, I saw two styles of pumps and one said "Open Systems (Stainless Steel or Bronze Construction)". Does this mean that I must use a Stainless Steel or Bronze Construction pump as the Garn is not a pressurized system?

 

[jebatty]

I think most use a cast iron pump rather than stainless or bronze for an open system. If the same water being heated by the system is used for DHW (no hx), then go with bronze or stainless. Follow Garn's directions, but I assume you will be using some water treatment for pH correction and possibly O2 scavenging. Isolation valves on the pump are good practice for any needed maintenance or replacement.

I used a cast Taco for over 10 years on an OWB open system without failure or issue. Now using it on my Tarm for 2 more years and still going strong.

 

[Sawyer]

Yes Jim, Garn does have a water treatment program. I will go with the cast pumps and isolation valves when considering my choices.

 

[Jim K in PA]

I am using Grundfos cast pumps. No need for the $$ of the non-ferrous pumps. Even though the Garn is non-pressurized, there is very little opportunity for O2 absorption, and the water treatment regimen, if followed properly with testing, should keep everything happy for years to come.

 

[Eric Johnson]

Even in a fresh water application, a cast pump like a Taco 007 will last for years. And then it's just a matter of spending $35 or so to replace it. That's been my experience.

 

[Sawyer]

Thanks again for the replies!