2" FPT attached to 1.5" bulkhead??

Raoul5Duke

Active member
Any problems attaching a 2" FPT to the outer threads on a 1.5" bulkhead? They seem to match up and I need to go from a 1.5" bulkhead to the 2" input on my Reeflo pumps.
 

RocketEngineer

Space is big.
If it is the inlet to a pump you need to drill for the inlet diameter and replumb. Restricting the inlet of a pump will cause cavitation issues if the flow is too high for the pump to draw properly.
 

Raoul5Duke

Active member
According to Reeflo, if the inlet and the outlet are the same then cavitation will not occur. Reeflos have a 2" inlet and a 1.5" outlet.
 

uncleof6

New member
According to Reeflo, if the inlet and the outlet are the same then cavitation will not occur. Reeflos have a 2" inlet and a 1.5" outlet.

Actually, that is true, to a point. Although the relationship between the inlet and outlet influence whether or not the pump will cavitate, the directions also say, do not restrict the pump inlet. What that means, is the reduction in the inlet size (to 1.5") is the same as putting a partially closed valve inline with the pump intake volute. Restricting the inlet as well as sizing the outlet larger than the intake (two variations of the same physics) will cause the pump to cavitate.

The pump is designed with a 2" intake, and 1.5" outlet (and not all reeflos have 2" in and 1.5" out; the pressure biased pumps are 1.5" in and 1.5" out. 2" is how you should run it, unless you want better flow by sizing the outlet up to 2". (Common practice when installing centrifugal pumps.) So if you want to run a flow biased pump that way, that's fine, but you will not be utilizing the pump to its fullest.

So the short answer to your original question is no you cannot attach pvc fittings to the external threads that are for the nut only; blulkhead—install/replace with a 2" bulkhead, run 2" pipe to the pump intake. If not, get a smaller wind up toy such as an iwaki et al. that will benefit from the 1.5" pipe rather than experience a performance decrease.
 
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