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Thread: Replacing pump with 2" fittings with one with 1-1/2" fittings and Pentair Rainbow 320

  1. #1
    Join Date
    Apr 2012
    IL, USA

    Default Replacing pump having 2" fittings with one having 1-1/2" fittings/Pentair Rainbow 320

    Hello. I am about to replumb my equipment pad and have two questions:

    1) I have a 35K gallon inground pool with three 1-1/2" intake lines combined into a single 2" pipe which feeds into my single speed, 1.5 hp pump which has 2" input/output ports which runs to my sand filter -> pool heater (also 2" ports for both) then splits into two 1-1/2" return lines. I believe the combined 1-1/2" intake line capacity and the combined 1-1/2" return line capacity allows the 2" plumbing/2" ports in my "equipment domain" to increase overall flow capacity over just having 1-1/2" PVC piping all the way through. Would you agree? However, my current pump is failing so I ordered a Pentair Superflo Variable Speed 1.5 hp pump which I just found out has 1-1/2" input/output ports (with unions that can be 1-1/2" or 2").

    So do the 1-1/2" input/output ports of the new pump now negate any benefits of having 2" PVC pipes in the "equipment domain"?

    2) I am thinking of replacing my current inline chlorinator with a Pentair Rainbow 320 inline chlorinator into my setup. However, the instruction manual states that if you have 2" piping but any of the pump/filter/heater have less than 2" fittings, then a minimum of 6" of 1-1/2" pipe must be installed at the inlet of the chlorinator to achieve enough pressure for proper operation.

    My question is if my pump has 1-1/2" inlet/outlet ports, then will adding a 6" "choke point" of 1-1/2" pipe in the middle of the 2" piping further constrict the flow at all (I suspect not)?

    I only use the inline chlorinator at the beginning of the season to establish a proper CYA level and then switch to manually adding liquid bleach. Or I'll also use it if I'm away for an extended period. If the answer is that the 6" pipe in the middle of the 2" pipe does reduce flow (though I suspect it doesn't), I will consider not adding the inline chlorinator at all and just using floating puck chlorinators for the few times I actually use puck chlorination.

    Thanks for your insights....
    Last edited by zak_michaels; 07-03-2019 at 04:13 PM.

  2. #2
    Join Date
    Apr 2012
    IL, USA

    Default Re: Replacing pump having 2" fittings with one having 1-1/2" fittings/Pentair Rainbow

    Addendum to original post. My current (failing) pump is a PAC FAB Centurion 8-168345-25. I cant find specific data on it but I just read something saying 1.5 hp pool pumps are typically always 1-1/2" inlet/outlets - so I may be mistaken on that point in my original post. However, the questions still stand:

    1) Does having 1-1/2" inlet/outlets on the pump negate any benefit of having 2" pipes in the equipment pad (where the intake and return 1-1/2" pipes are combined into 2" fittings)?

    2) If the pump has 1-1/2" inlet/outlets and the other pad equipment all have 2" ports/2" pipes, does inserting a 6" long 1-1/2" pipe (leading into the chlorinator) have any impact on flow rate since the pump's inlet/outlets are 1-1/2"?

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