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Thread: Help selecting best venturi tee nozzle size

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    Help selecting best venturi tee nozzle size

    I have a 6x6 square spa with four jets connected via 2" PVC to intelliflow VS pump which is used used for both pool/spa. The venturi jets are connected to a 2" air pipe which extends approx 15' from my spa. Spa is located approximately 50' from pool equipment pad and is connected via 2 piping.

    I noticed my existing venturi tee nozzles are 1/4" and assume I should I should swap these out with 1/2" or 7/16" venture nozzles to get better performance? Should I also change the return size on each jet? Return jet openings are 1.5 (rings w/o eyeball)?

    If it matters venture tee nozzles are recessed approximately 10 behind the return jet opening.

    Thanks in advance for recommendations.

    -Brian

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    mas985's Avatar
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    Re: Help selecting best venturi tee nozzle size

    There are a couple of issues when going to larger jet sizes. First, in order to get the same exit pressure, you need higher flow rates for larger jets. This can be a problem because the plumbing may not support it. So for a 1/4" jet, you only need 7 GPM/Jet to achieve moderate pressure while for a 7/16" jet, you will need 19 GPM per jet. Since you have 4 jets that would be a total 76 GPM which doesn't sound too bad as long as the pump can produce that with the head loss in all parts of the plumbing.

    If you can tell me the filter pressure when the pump is running the jets, I can estimate the flow rate of the jets with the old and new jets. Also what kind/size filter do you have?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Help selecting best venturi tee nozzle size

    Filter is a clean and clear 200 cartridge filter.

    15 PSI @ 2,300 RPM @699 W
    22 PSI @ 2,800 RPM @ 1,177 W
    26 PSI @ 3,000 RPM @ 1,424 W
    30 PSI @ 3,200 RPM @ 1,705 W

    I am also attaching links to pictures of plumbing during construction. Return lines are 2" and I believe 4" on drain line connected to two VGB drains in spa floor.
    Other plumbing in the photo is the blower line for floor air vents and retractable spa fountain.

    http://1.bp.blogspot.com/-qSk5_cC0yu...0/DSC_0407.JPG
    http://2.bp.blogspot.com/-rMorId0Foy...0/DSC_0427.JPG

    Thanks for the help!

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    mas985's Avatar
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    Re: Help selecting best venturi tee nozzle size

    Are you sure the jets are 1/4"? The pressures that you posted are more indicative of 3/8" jets which are the most common type used in spas.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Help selecting best venturi tee nozzle size


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    mas985's Avatar
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    Re: Help selecting best venturi tee nozzle size

    You have the full size Intelliflo and not the i1 or i2?

    When running the spa, is any of the water diverted to other returns (floor or fountain) besides the jets?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Help selecting best venturi tee nozzle size

    Full size Intelliflo VS. I have four jets in the spa and an additional return that only runs when in pool mode.

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    mas985's Avatar
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    Re: Help selecting best venturi tee nozzle size

    The spa floor pipes are only for air? No water?

    Do the jets feel really strong almost too strong at 3200 RPM?

    Also, it might be helpful if you could post a picture of the pad equipment and plumbing.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Help selecting best venturi tee nozzle size

    Just air from blower at poolpad for the floor pipes and jets do not feel too strong.

    Here are some pics during construction:
    http://4.bp.blogspot.com/-QCTvmcsmwq...0/DSC_0555.JPG
    http://4.bp.blogspot.com/-X2talvYIw-...0/DSC_0500.JPG

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    mas985's Avatar
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    Re: Help selecting best venturi tee nozzle size

    Best I can tell, flow rate is around 60 GPM @ 3200 RPM which would be around 15 GPM per jet and should be more than enough for the jets so it is surprising that the jets do not feel that strong. But again, I was expecting much higher filter pressure for 1/4" jets so my first thought was that some of the water was getting bypassed around the jets. Something isn't adding up here and I am not sure what is going on.

    Have you tried removing the jet nozzles and running without them? What is the filter pressure then?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Help selecting best venturi tee nozzle size

    I removed jets. New ratings as follows. As it relates to my original statement I should clarify that jets always felt powerful. My assumption was that the opening on the venturi nozzles should be larger based on only having four jets and that this would up the performance. On another note my regular setting for SPA is 2,300 while it heats up. When operating at this speed my Intellichlor IC60 does not kick on (low flow). That leads me to believe I am just under or right around 25GPM @ 2,300 RPM.

    Pressure w/o ventur T's (2" pipe to spa, 1 1/2: pipe in gunite wall with 1 1/2" return rings directing water into spa:

    14 PSI @ 2,300 RPM @ 775 W
    19-20 PSI @ 2,800 RPM @ 1,348 W
    22 PSI @ 3,000 RPM @ 1,665 W
    24 PSI @ 3,200 RPM @ 2,035 W

    Thanks again for all the help!

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    mas985's Avatar
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    Re: Help selecting best venturi tee nozzle size

    15 PSI @ 2,300 RPM @ 699 W
    That should be resulting in about 45 GPM so the SWG should be fine with that. The Intellichlor normally has a bypass with a small check valve. If that isn't closing at the lower flow rates, that might explain why there is not enough flow rate.

    As it relates to my original statement I should clarify that jets always felt powerful. My assumption was that the opening on the venturi nozzles should be larger based on only having four jets and that this would up the performance.
    If the jets are now powerful, I don't understand this statement. Exactly what are you trying to achieve. When you widen the orifice in the jet, it will generally make the jets fell less powerful unless you can increase the flow rate to the jet.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  13. Back To Top    #13

    Re: Help selecting best venturi tee nozzle size

    If I bypass the heater my readings are as follows in SPA mode (with venturi T nozzles removed):

    9 PSI @ 2,300 RPM @ 876 W
    15 PSI @ 2,800 RPM @ 1,510 W
    17 PSI @ 3,000 RPM @ 1,822 W
    19 PSI @ 3,200 RPM @ 2,205 W

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