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Thread: materials suitable for flexible lines

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    materials suitable for flexible lines

    hi folks. i bought a coil of flexible PVC hose here for my tub install, and soon after happened to see a small tub plumbed entirely with vinyl tubing. i read up and learned that vinyl is PVC, so their heat rating is the same. the vinyl seems easier to work with and less expensive; some even have a braided structure to stay round. is there another reason the less flexible "flexible" stuff is preferred by pool and spa builders?

    similarly, is there any reason to avoid rubber hoses?
    plumbing up wall-mounted equipment and plenty gauges below a 500G wooden outdoor hot tub.

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    Re: materials suitable for flexible lines

    Most pool builders don't use flexible pvc. Most use rigid pvc. If you look at the photos of the pool builds here you will see very little flexible pvc. Generally pool builders feel that flexible fails more. Our experience on this forum supports that belief.

    Portable spas use the flexible because of their tight spaces -- its just simpler to work with. I suspect they use it because they feel it will last longer than vinyl and they know it will hold up to the chemicals run through a spa.

    That is why you need to stay away from rubber -- eventually it will react with something.
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    Re: materials suitable for flexible lines

    thanks, you're quite right, i didn't acknowledge that flexible is the poor cousin to rigid. i figured it would be easier to work with for the long lines and that may not even be true.

    my real interest is at the pumping station, where i positioned a number of components in sequence: drain valve -> pump -> filter, and heater -> flow switch -> flow gauge. i will quickly know if there is a leak and want to use the most flexible material i can. it sounds like vinyl may be safe than rubber.

    mcmaster-carr's document on PVC chemical resistance:
    http://www.mcmaster.com/#8354kac/=10bfgzw
    plumbing up wall-mounted equipment and plenty gauges below a 500G wooden outdoor hot tub.

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    Re: materials suitable for flexible lines

    Chemical and temperature resistance are just 2 concerns for pipe selection. Others concerns are strength (pressure rating), longterm bondability (can it stay glued), UV resistance (if outdoors) and general durability.

    Flexible vinyl tubing fails in almost all those performance areas.

    Pressure rating - in 1-1/2 size, pressure rating of unreinforced vinyl is around 25psi. Reinforced vinyl isn't much better. That's unsuitable, as it's right at the normal operating range of most pumping systems. Rigid PVC is in the 350psi range.

    Longterm bondability - Vinyl is heavily loaded with plasticizers, (compounds which impart flexibility to vinyl). Plasticizers are well know to interfere with bonding and tend to migrate and weaken bonds over the long term. Flexibility at joints tends to promote joint failure by allowing the bond to "peel" apart. Glued joints are weakest to peeling forces.

    UV resistance - most all clear plastics are prone to rapid deterioration from UV.

    Durability - whether it be dropping a rake or some other object or being hit by a sharp edge, vinyl is substantially less durable than common rigid PVC pipe.
    21K gal 16' x 40' in-ground pool built 1959, old school with Jacuzzi bronze pump, American Products 24" Sand Filter & Americana Multiport valve, Jandy Lite2 millivolt heater, Coverstar cover, and classic Kreepy Krauly.

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    Re: materials suitable for flexible lines

    thank gtemkin, that taxonomy is very helpful. so, for in my protected outdoor pumping station with a tiny pump, i will need a UV-resistant, chlorine-resistant, pressure-rated tubing, and to put it on hose barbs instead of using glue. i am leaning towards using this product:

    McMaster-Carr

    UV-Resistant Black PVC Tubing
    Very flexible
    Semisoft (Shore A70)
    Temperature Range: -10 to 175 F
    Use with barbed fittings
    Great for outdoor use, this opaque black tubing protects light-sensitive fluid, plus it resists degradation caused by exposure to ozone and UV light. Use with water, air, food and beverage, and bleach. Tubing is made from FDA-compliant resins. It can be sterilized with steam (autoclaving) and gas.
    plumbing up wall-mounted equipment and plenty gauges below a 500G wooden outdoor hot tub.

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    gtemkin's Avatar
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    Re: materials suitable for flexible lines

    Working pressure specs are pretty low. Do you have a pump or is a convective flow style heating system. If pump, do you know what the running pressure is?
    21K gal 16' x 40' in-ground pool built 1959, old school with Jacuzzi bronze pump, American Products 24" Sand Filter & Americana Multiport valve, Jandy Lite2 millivolt heater, Coverstar cover, and classic Kreepy Krauly.

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    Mod Squad zea3's Avatar
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    Re: materials suitable for flexible lines

    The flexible spa hoses tend to develop pinhole leaks, so if you use it only put it in easily accessible areas.
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    Re: materials suitable for flexible lines

    both excellent points. gtemkin, thanks for pointing out the pressure rating (30psi for 3/4 line). the Laing E5 pump is rated at 50psi max... but would only reach that point running with zero head?

    zea3, good to know that's the failure mode. if i even use them, i won't bury the long flexible lines.
    plumbing up wall-mounted equipment and plenty gauges below a 500G wooden outdoor hot tub.

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