Liner fading/bleaching/yellowing in return jet path?

[Auburn02]

Trying to determine if my eyes are playing tricks, if this is a chemistry issue, or if this is just the way it is and I'm going to have to accept it.

We've had our pool completed for about 2.5 years now, and this winter I started to notice the first area of discoloration of the liner. I get that it's inevitable with vinyl liner pools but this is the first time I've seen one that didn't just fade evenly with time, but at least appears to be directly related to the output from one of the returns.

This is on our sunshelf, so it gets much more direct flow from a return jet than other areas of the liner. I also previously had the return jet intentionally aimed at the surface of the shelf to be able to blow debris off of the shelf where the Dolphin can get to it, but since noticing this I've redirected the jet to just focus on the surface of the water instead.

So is this normal? I manipulated some settings on the photos to highlight the areas but in person it really is quite noticeable (to me) - maybe not to the casual guest, but it's definitely has a yellow/green/bleached out tinge to it. Anything else I should check or try?

As far as chemistry, I will admit to the FC being on average on the higher side of normal with a couple of SLAMs in the 2.5 years. Again though if you told me that would cause the whole liner to fade faster ok, but is the water being pumped out immediately after passing through the SWG really that potent that it would cause a discoloration immediately at the point of the return exit?

Going to submit this thread from my PC and then attach pics from my phone...

 

[Auburn02]

Pics. Yellow lines highlight the directional flow of the wall return over the sun shelf and where the discoloration is concentrated.

 

[mknauss]

Shallow water results in less UV protection. UV is what impacts liner colors unless you are dumping solid chlorine in that area. Hopefully not with a SWCG.

 

[YippeeSkippy]

Chemistry test results?
FC
CC
pH
TA
CH
CYA
Salt if applicable

 

[Auburn02]

Shallow water results in less UV protection. UV is what impacts liner colors unless you are dumping solid chlorine in that area. Hopefully not with a SWCG.

A good point, I don't think I'd be as shocked if the entire shelf faded faster than the rest of the pool, but (and I don't know that the pictures really do it justice) it certainly seems concentrated in the area immediately in the flow of that particular return jet.

The only time I dump solid chlorine is when I've had to SLAM or in colder weather when the SWCG is not operable, and when that occurs I dump into the flow of the jet in the deep end.

 

[mknauss]

The only time I dump solid chlorine is when I've had to SLAM or in colder weather when the SWCG is not operable, and when that occurs I dump into the flow of the jet in the deep end.

Is that the jet pointed to this area?

 

[Auburn02]

Chemistry test results?
FC
CC
pH
TA
CH
CYA
Salt if applicable

Most recent results (FC has been falling as the temps are warming and I have not yet adjusted the SWCG):

FC: 3.0
CC: 0.0
pH: 7.5
TA: 50
CH: 50
CYA: 20
Salt: 2800

Going back over the past four months or so there was a several month span where CYA was 30-40 and FC was in the 8.5-10.5 range. The pool gets very little sun in the winter and I was adjusting the SWCG down incrementally but probably let FC stay above the recommended range for a few months straight.

 

[Auburn02]

Is that the jet pointed to this area?

No, the jet I dump the liquid chlorine in front of is across the pool, about as far from the sun shelf as possible.

In the second picture you can see a PVC fitting across the pool, that is a deck jet but the return is almost directly below there.

 

[YippeeSkippy]

Truthfully, I can barely see the difference. You of course see it all. Nature of the beast.
The only advice at this point I can see is to make sure the jet return isn't aimed down but rather out straight yet still under the water and see if that helps?

 

[Bperry]

A fun experiment might be to aim the jet somewhere else and see if the yellow spot goes away or moves.

 

[Auburn02]

Truthfully, I can barely see the difference. You of course see it all. Nature of the beast.
The only advice at this point I can see is to make sure the jet return isn't aimed down but rather out straight yet still under the water and see if that helps?

Agreed, certain angles and lighting conditions it’s more obvious but certainly is far “worse” to me than likely anyone else who would look upon the pool.

But your suggestion is what I’ve done so far, just moved the return outlet up parallel to the water and not down to blow off the shelf.

A fun experiment might be to aim the jet somewhere else and see if the yellow spot goes away or moves.

Not a bad plan. Just reverse all three to have the pool circulate clockwise instead of counter clockwise and check it again in a couple years.

I will at least try some vitamin C tabs for good measure, but if iron were the culprit I’m not sure there would be any explanation for the staining to only occur on the shelf in the path of that one return.