Connecting a 1" circulator pump to an 1-1/4" flange - any issue?

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Old 11-19-13, 05:55 AM
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Connecting a 1" circulator pump to an 1-1/4" flange - any issue?

I've got 1-1/4" isolation flanges and a pump with a 1" inlet/outlet. Seems like the bolts line up and gasket would seal. Would the abrupt change is size right at the pump cause turbulence or other issues?
 
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Old 11-19-13, 07:29 AM
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I'm going to say that it would probably be fine... pumps themselves don't actually have 'sizes', but the pump needs to be appropriate for the amount of water that must be moved against whatever resistance (system 'head') the system piping imposes.

What make/model is the pump?

I presume that the are 1-1/4" because the piping is that size?
 
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Old 11-19-13, 07:43 AM
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Probably be OK, I think. But, it is best to have a straight run of at least 10+ pipe diameters on the suction side of the pump. You can try it and see if there is unusual flow noise or cavitation. Discharge side isn't important.

Why didn't you choose a 1-1/4" pump model?
 
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Old 11-19-13, 08:07 AM
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Thanks for the feedback. Very helpful. The pump is a grundfos alpha 15-555/lc and I chose it because it is adequate for my system of 100k btus and numerous short zones. But, I've safeguarded for an upgrade in the system by running 1-1/4" pipe because I may develop portions of my attic and basement in 5 or 10 years and wanted to reduce hassle. I got the used DE 04 peerless propane boiler for free and it's sized right for my current operation.
 
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