I believe the regular pump flanges are interchangeable between Taco and Grundfos pumps, for example (and presumably others too,) thus allowing us to swap out different brands of pumps without changing flanges. But it is unclear whether the pumps with 1-1/4" unions can also be swapped out with different brands. Here is an example:
Taco pump with 1-1/4" union connection
Grundfos pump with 1-1/4" union connection
Here is Grudfos' half-union.
Here are specs on the Taco half-union, which is very hard to find anywhere, and (& perhaps BECAUSE) it costs twice the cost as the Grundfos version.
I've seen contradictory specs on them. Some sites say the Taco half-union is a 1-1/4" DIN thread. Some say it is NPT (which is certainly wrong for the mating threads in the union). Yet a third brand (Armstrong) is purportedly NPSM threads in the union. I don't have confidence in ANY of the specs, as I've found plenty of them that contradict each other.
Typically, one brand of union is not compatible with another, as the mating threads are not standardized. But it's unusual to even be able to buy a half-union (likely for this very reason). I kindof *suspect* these are indeed standardized, but I'd sure like to get confirmation from someone with a lot of experience swapping out pumps with 1-1/4" union connections of different brands. It seems like it would be odd for these manufacturers to go out of their way to make the other flanges the same, but then make the sortof-standard 1-1/4" union NOT the same.
Can anyone confirm or deny compatibility of the 1-1/4" half-unions for Taco vs. Grundfos?
Taco pump with 1-1/4" union connection
Grundfos pump with 1-1/4" union connection
Here is Grudfos' half-union.
Here are specs on the Taco half-union, which is very hard to find anywhere, and (& perhaps BECAUSE) it costs twice the cost as the Grundfos version.
I've seen contradictory specs on them. Some sites say the Taco half-union is a 1-1/4" DIN thread. Some say it is NPT (which is certainly wrong for the mating threads in the union). Yet a third brand (Armstrong) is purportedly NPSM threads in the union. I don't have confidence in ANY of the specs, as I've found plenty of them that contradict each other.
Typically, one brand of union is not compatible with another, as the mating threads are not standardized. But it's unusual to even be able to buy a half-union (likely for this very reason). I kindof *suspect* these are indeed standardized, but I'd sure like to get confirmation from someone with a lot of experience swapping out pumps with 1-1/4" union connections of different brands. It seems like it would be odd for these manufacturers to go out of their way to make the other flanges the same, but then make the sortof-standard 1-1/4" union NOT the same.
Can anyone confirm or deny compatibility of the 1-1/4" half-unions for Taco vs. Grundfos?
