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

[rock]

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?

 

[Melt In The Sun]

Re: Does it functionally matter which way a union o-ring fac

Nope, either way is fine.

 

[clayg]

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.

 

[Bama Rambler]

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.

 

[rock]

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.

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.