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Thread: challenging pvc problem

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    challenging pvc problem

    I'm going to build a 1000 gallon spa outside my slab-on-grade house. My original intent was to heat the spa with the 130,000 Btu/hr output high efficiency hot water heater augmented with solar panels on the roof. The "boiler room" is in the back corner of the house and my heating contractor/spa specialist POSER who didn't have a clue what he was doing placed a 4" pvc chase under the slab to the spa location 80' away with only a pair of Rehau Pex (only 13/16" inside diameter) to heat the spa. The slab is poured, the house is built. The spa is the last step before I'm finished. Once I excavate for the spa I'll yank the undersized Pex pair out and replace it with schedule 40.

    But the largest suction/returns schedule 40 pipe I can fit inside the 4" chase is two 1/5" diameter pipes ' and they only fit if I use "repair couplings" aka "flush inside slip couplings" (they're the same outside diameter as the 1/5" schedule 40 pipes and made so they have 2 street ends or spigot ends [2 ways to say the same thing]. They reduce the ID of the pipe at the connection, so I'll lose some flow there, but as I'll only need 3 pairs of them to get to the boiler room and back, it shouldn't be too bad.
    My big problem is this: I can't find any made as elbows. They're all straight. I've tried plastic oddities, spears, nibco, and midland and nobody knows where I might find 45 degree elbows made that way. It'll take 2 pairs of 1.5" 45 degree elbows to get thru the pair of 4" 45's that I created the sweeping elbow with that gets me from under the slab to above it in the boiler room.

    The only solutions I've come up with are heat bending some sections to try creating the shape I need, then reaching them into the 4" pvc from above the slab and gluing them to some repair couplings that I'll have prepped on the ends of the 1.5" pipes that I've stuck thru from 65' away outside. It's either that, or I have to take out a section of 4.5" slab, cut off the 4" sweeping turn, poke the pair of 1/5" pipes thru, use conventional fittings to get back above the slab, then sleeve and bush them to protect them from being solidly poured in the slab. Does anybody have a better idea?

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    Mod Squad jblizzle's Avatar
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    Re: challenging pvc problem

    I can not picture how you would be needing to put and get turns inside a conduit under concrete ...

    Have you considered using flex schedule 40 PVC? At least then you would not need the inside couplers that will restrict flow.

    Also that pipe is generally too small for the high flow rates needed for a spa. But if it is just used for a heating/filtering loop that could work. With a separate plumbing loop and pump closer to the spa using larger pipe for the jets.

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    Mod Squad Bama Rambler's Avatar
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    Re: challenging pvc problem

    I don't normally recommend flex, but in this case I agree with JB, it's probably your best bet. You can also buy it in rolls so you won't need any couplings.
    Dave J. TFP Moderator
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    UnderWaterVanya's Avatar
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    Re: challenging pvc problem

    Quote Originally Posted by jblizzle
    I can not picture how you would be needing to put and get turns inside a conduit under concrete ...

    Have you considered using flex schedule 40 PVC? At least then you would not need the inside couplers that will restrict flow.
    I'm thinking - and I could be wrong - that the elbows are ONLY for the ability to go from parallel to the ground to perpendicular to the ground. Like this:

    L________ The "L" needs a 90 degree elbow if the pipe "___" is below grade and the equipment is above grade.
    Inlaws Pool Boy since June 14th 2012, Pool built ~ 2003, In-Ground, 16'x32'
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    UnderWaterVanya's Avatar
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    Re: challenging pvc problem

    Questions for the OP:

    • What is 1/5" pipe? If that's 1/5th I'm confused since 13/16th's is a lot bigger.
      What is the reason for two pipes - is one outgoing (return) and one a (suction) bringing water back?
      Can you fit more than two pipes in the conduit - perhaps paralleling the existing pair of 13/16th's?
    Inlaws Pool Boy since June 14th 2012, Pool built ~ 2003, In-Ground, 16'x32'
    13500 gal, Vinyl Liner, Fiberglass Slide, TF-100 Test Kit, Hayward 210T
    sand filter, A.O. Smith 1.5HP main pump motor (C48L2N134C1),
    Hayward SuperPump (model ?), Polaris 380 & PB4 Booster Pump

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    Re: challenging pvc problem

    I'm sorry, I mis-typed 1.5" and instead typed 1/5" pipe a few times.
    Jason et al, it very well may be that flex pvc is the way to go, but other forum posts (from here and elsewhere) have me scared of it. Maybe I just need to build it to be accessible for replacement if necessary. I was/am hoping someone might have a better solution than flex or what I've come up with as a plan to avoid flex while still getting larger pipes in place to replace the PEX (which is banned for this use anyway since it can't stand up to chlorine etc).
    I'll try again to be clear about what I propose: Picture a 4" pvc raceway (aka "chase") running horizontally under the slab. Now picture a 45 degree elbow sloping up thru the slab, followed by a 4" straight section of pipe, followed by another 45 degree elbow and you've got my "sweep elbow" assembly thru the slab. I propose to push two 1.5" schedule 40 pvs pipes (already fixed with flush inside slip couplings glued to the ends of them) thru the 4" pipe from outside till they dead end at the first 45. From above the slab, I should be able to reach inside with pre-bent sections of schedule 40 pvc and glue on the bent pieces by pushing them onto the pre-installed couplings. It'll require getting it right first try - or I'll have to bust up the slab to make it right. And you're right about my pipe sizing. Since the Poser radiant heating/spa contractor undersized the suction/return chase, I will only be able to run filtration and maintenance temps from the house. For spa jets and time-of-use heat-ups, I'm forced to install a separate system in the basement of the nearby gazebo. 2 pipe systems: (1) Filtration, propane maintenance heat, and salt water chlorine generator to be run thru the 1.5" pipes passed under the slab thru the chase. And (2) Electric quick-heat plus spa jets run using 2.5" and 2" pipes from the nearby gazebo basement. The reason I don't do it all from the gazebo basement is that besides being a difficult space to work in, I really want to augment my spa heat with rooftop solar panels piped with a heat exchanger.

    Here are some results from this and other forums:
    I was advised to use copper or PEX on another forum, but since I want to make a salt water spa, copper is OUT as there are many problems associated with copper and salt pools and spas. Also, PEX is banned for use in pools (and by association, in-ground spas, as far as I'm concerned). And for that reason, I'd have to remove the PEX suction and return lines put in by the poser contractor even if they weren't too small.
    Another person informed me that PVC is illegal as supply lines inside a house. That turned out to be true, but I'm wondering if it applies to me because I'll be connecting it to a heat exchanger, Not the domestic supply. I had thought it might be nice to add water to the spa by piping into my return in the boiler room from my domestic system - much of which IS piped with PVC in the boiler room before swapping over to copper into the water heater and PEX to the household fixtures.
    Flex IS attractive from an ease of installation perspective - and termites shouldn't be a problem since it'll be encased in the 4"pvc chase, but still, it will be underground and there Are termites around here. Also, since pipe expands/contracts with heat/cool cycles, it might not hold up to friction where it contacts the bends in the chase. Anybody have any more thoughts on a better fix than I've envisioned or how I could avoid the weaknesses of flex?

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    Re: challenging pvc problem

    Unfortunately I can't see a better way than flex. Not to be discouraging but I don't foresee you being able to get sch40 in and getting it glued. You might get one but I really doubt you will get the second one.
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    Mod Squad Bama Rambler's Avatar
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    Re: challenging pvc problem

    Don't be scared of flex. It's pretty tough. In your situation where it's protected and fairly easy to get to, I wouldn't be scared to use it at all. Termites won't go seeking it out, they just don't avoid it if they encounter it in their normal foraging route. Protected like yours will be, you won't have that problem at all.
    Dave J. TFP Moderator
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    Re: challenging pvc problem

    Thanks guys, I really appreciate the input. Even considering I'd get a better gpm thru flex, I'm going to try the rigid install. The reason is, besides the termite situation (which I agree with Dave that I probably won't have them seeking it out) I'm afraid the water hammer of the pump cycling over time will cause it to wear itself out in the turn. I know this means more work for me in the short term, but I Really don't want trouble down the road. Pay now, play later.
    thanks again,
    scrappy out

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