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Thread: Spa plumbing question

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    Spa plumbing question

    First time poster and first time pool owner. This is an outstanding site and I look forward to using it quite a bit as a new pool owner. My pool is under construction right now and I have a question about the plumbing for my raised 8 foot spa with 6 jets. I have 3 inch pvc pipe coming from the spa drains going to the pump where it reduces down to 2 inches to go through the pump, filter and heater and then the builder has planned (not done yet) 2 inch pvc pipe back to the spa which is 90 feet from the equipment pad. My question is should I increase the return pipe size after the heater to 3 inch pipe like the suction. Builder states I wouldn't gain much since 2 inch is running through the pump, filter and heater. I am very new to this and have researched this for multiple days and can't seem to figure out what is the best option.
    Pool Build in progress, 21x42 freeform gunite 3.5 to 8 feet deep with additional 11x20 beach entry to tanning ledge (35k), 2 foot bond beam wall with four 2 foot sheer descents and raised 18inch 8 foot spa on top of the bond beam wall. Hayward 3400 vsp for pool/spa combo, Hayward 1.5Hp for 4 sheer descents, 400k btu heater, Hayward 450sf cartridgefilter

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    Mod Squad jblizzle's Avatar
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    Re: Spa plumbing question

    Welcome to TFP!!!

    Larger pipe lowers head loss, this is more pronounced on the suction side. It would certainly not hurt to run the larger pipe from the spa return valve to the spa (which is a long distance) and then reduce back to 2" in the gunite if required.

    Doing so will allow you to run the pump a little slower (saving power) and still have adequate flow rate for the jets.

    But, builder is right it likely will not make a huge noticeable difference since you are able to dial in your pump speed.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Re: Spa plumbing question

    Thanks for the quick response. Would I get the same results running two 2 inch lines in parallel instead of one 3 inch line from the spa return valve to the spa which will reduce to 2 inches in the gunite at the spa. Also, does the larger pipe help to heat the spa quicker. Thanks
    Pool Build in progress, 21x42 freeform gunite 3.5 to 8 feet deep with additional 11x20 beach entry to tanning ledge (35k), 2 foot bond beam wall with four 2 foot sheer descents and raised 18inch 8 foot spa on top of the bond beam wall. Hayward 3400 vsp for pool/spa combo, Hayward 1.5Hp for 4 sheer descents, 400k btu heater, Hayward 450sf cartridgefilter

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    Mod Squad jblizzle's Avatar
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    Re: Spa plumbing question

    Pipe size will not have any impact on the heating rate.

    You generally do not want the return pipes to be larger than the suction pipes. Two 2" pipes is slightly less cross-sectional area than One 3" pipe, so that would be fine (and maybe cheaper for the material too). If you do that, have them feed the jets on opposites sides of the loop.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Re: Spa plumbing question

    Thanks for all the info. The gunite has already been put in so no option of feeding the jets on opposite sides of the loop. I had the builder change and put in the 3 inch drain in the spa right before the gunite was put in. So I will have a 3 inch suction line to the pump, and 2 inch return line to the spa with a 2hp blower going through it's own 2 inch line. I was just concerned with the 90 foot run from the equipment to the spa, but it sounds like I will be OK. They are running the rest of the long plumbing in a couple of days so now would be the time to change it if needed. Is there any value added in running the two 2 inch lines in parallel if they just combine before the spa and go into one 2 inch line that feeds all 6 jets? Thanks again.
    Pool Build in progress, 21x42 freeform gunite 3.5 to 8 feet deep with additional 11x20 beach entry to tanning ledge (35k), 2 foot bond beam wall with four 2 foot sheer descents and raised 18inch 8 foot spa on top of the bond beam wall. Hayward 3400 vsp for pool/spa combo, Hayward 1.5Hp for 4 sheer descents, 400k btu heater, Hayward 450sf cartridgefilter

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    Mod Squad jblizzle's Avatar
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    Re: Spa plumbing question

    Yes. They will be lower head loss and therefore a higher flow rate at a lower RPM of the pump.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Re: Spa plumbing question

    Thank you very much. That is what I will do. I really appreciate the advice.
    Pool Build in progress, 21x42 freeform gunite 3.5 to 8 feet deep with additional 11x20 beach entry to tanning ledge (35k), 2 foot bond beam wall with four 2 foot sheer descents and raised 18inch 8 foot spa on top of the bond beam wall. Hayward 3400 vsp for pool/spa combo, Hayward 1.5Hp for 4 sheer descents, 400k btu heater, Hayward 450sf cartridgefilter

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