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Thread: Does it functionally matter which way a union o-ring faces?

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    Does it functionally matter which way a union o-ring faces?

    QUESTION:
    When using a repair union, does it matter (from a future leak perspective) which way the o-ring faces?

    DETAILS:
    I learned from this forum (specifically the BBB method) that the mineralizer on the output of my filter was probably useless.
    But I didn't remove it until this week, as I tried to repair every leak in my equipment.


    I first considered this telescopic union (aka expansion coupling) for the repair, but the o-ring location worried me:


    Apparently I'm not the only person worried about that o-ring location, as this DIY guy did the same thing I did (which was not to use the telescopic expansion coupling for fear of leaks):
    http://www.troubleshooters.com/pool/rep ... _Couplings

    So, in the end, I used a schedule 80 union (I could not find any schedule 40 unions in the store):


    My question:
    Since the o-ring location is clearly asymetric with respect to the flow of water, does it matter (from a leak perspective) which way I put the union on the plumbing?
    Silicon Valley, 38,500 gallons in-ground plaster; Sta-Rite System 3 Model S8M150, 259 sqft cartridge 25022-0203S + 191 sqft cartridge #25021-0202S = 450 sqft filter@0.28gpm/sqft = 125 gpm@50psi max. Three 220v Sta-Rite Max-e-Glas II pumps {AO Smith QC1102 1.0x1.65SF for filter + cleaner; SQ1152 1.5x1.47SF for spa jets; square 48Y flange}. 13 Fafco 12'x4' professionally installed "Revolution" solar heating panels + Raypak RP2100 P-R 405A-EP LPG 399,000/hour heater + Compool Lx3600 controller + Infinity 4000 automatic pool cover (120v 3/4 HP motor); both skimmers are NOT filtered & serve only as intake for 9-port water valves (aka cleaner heads) controlling fifteen Paramount PCC2000 3" self-cleaning jets with the optional Debris Containment Canister.

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    Melt In The Sun's Avatar
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    Re: Does it functionally matter which way a union o-ring fac

    Nope, either way is fine.
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
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    Re: Does it functionally matter which way a union o-ring fac

    No. So long as the seal is good, the union does not care which way it faces.

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    Mod Squad Bama Rambler's Avatar
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    Re: Does it functionally matter which way a union o-ring fac

    Technically is does matter, BUT the flow in our pool systems isn't nearly enough for it to be a problem. So practically, it makes no difference at all in your case.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: Does it functionally matter which way a union o-ring fac

    Quote Originally Posted by Bama Rambler
    Technically is does matter, BUT the flow in our pool systems isn't nearly enough for it to be a problem. So practically, it makes no difference at all in your case.
    I thought that might be the case, because it is asymmetric; so it must make a difference, albeit perhaps slight.

    The good news is that, with the replumbing of the filters and removal of the mineral-exchange thing on the filter outlet, I've eliminated all but one leak, which happens to be at the non-standard proprietary hardware outside the filter (which isn't on the filter drawings). Sigh.


    If I can figure out which o-ring these proprietary STa-Rite 2" unions use, I just might be able to plug up the last leak.
    Silicon Valley, 38,500 gallons in-ground plaster; Sta-Rite System 3 Model S8M150, 259 sqft cartridge 25022-0203S + 191 sqft cartridge #25021-0202S = 450 sqft filter@0.28gpm/sqft = 125 gpm@50psi max. Three 220v Sta-Rite Max-e-Glas II pumps {AO Smith QC1102 1.0x1.65SF for filter + cleaner; SQ1152 1.5x1.47SF for spa jets; square 48Y flange}. 13 Fafco 12'x4' professionally installed "Revolution" solar heating panels + Raypak RP2100 P-R 405A-EP LPG 399,000/hour heater + Compool Lx3600 controller + Infinity 4000 automatic pool cover (120v 3/4 HP motor); both skimmers are NOT filtered & serve only as intake for 9-port water valves (aka cleaner heads) controlling fifteen Paramount PCC2000 3" self-cleaning jets with the optional Debris Containment Canister.

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