Yellowing of liner and equipment

[bmtrimp]

My liner is yellowing (especially in the white areas) as well as the baskets in my skimmer and pump. I thought maybe it was my liner getting old but why would my baskets yellow too? I have tried googling and searching for an answer but could not find anything. I've tried super chlorinating to remove it with no luck, I've had my water tested and there we no significant levels of copper or iron in the water. Everything else was in check. The pool tech at the store said that my water was practically perfect and they didn't know why i would have yellowing on these areas as well. I tried to scrubbing with my hand to see if the yellow go away and it does not. The pool tech recommended "off the wall" from bioguard to scrub the areas but not only does the entire pool need scrubbed (along with baskets) but it seems like a "i don't know so here" kind of response. I haven't changed anything in my process from last year to this, the only major changes i made this year is new filter sand. I can't imagine that the sand did that though. (I used majestic white II) My setup should be in my sig.

Any thoughts? Thanks!

 

[JoyfulNoise]

Go get a Mr. Clean MagicEraser sponge and try to scrub a small area somewhere (inside the skimmer, the weir door, whatever) and let us know what happens. If the yellowing rubs off, then there's a couple of different explanations. After you clean a small test area with the sponge, go to a different area and try a vitamin C test. Just put a bunch of crushed up vitamin C tablets in an old nylon and hold it against a yellowed surface for about 5-10mins (may not even need that much time). Let us know if the stain lightens or disappears.

 

[bmtrimp]

Well the vitamin C took it right off while the Mr. Clean took some persistence and didn't do as well as a job like the C. I'm guessing it's rust staining. Any ideas on why i'm seeing this. I use city water and the water test didn't show any iron. Any way to easily treat the whole pool? Thanks for your help!

 

[JoyfulNoise]

Iron would never show up on a municipal report because iron is not considered a drinking water contaminant. So municipal-supplied waters can have iron in them. Is your municipal supplier using any kind of metal sequestering agent? Many use phosphonate sequestering agents but they don't always have to report the level. You can call and ask and they should be able to tell you.

So yes, it is iron staining. What's happening is the plastic parts are becoming slightly porous with age and water exposure (happens to all plastics and rubber in water) and that additional little bit of roughness makes the perfect surface for iron to scale out onto. The vitamin C is removing it and putting it back into solution in your pool while while the Mr. Clean sponge is just mechanically removing the roughness. Mr Clean sponges are made of melamine foam which has a very fine micro-roughness to it that acts a lot like sandpaper. It's often used as a finally polishing step on metal surfaces to buff the surface oxides smooth.

Anyway, you can treat with vitamin C (ascorbic acid) with a spot cleaning approach or use the magic eraser to try to get at it. Sadly, it's just going to come back. The iron levels in the water can be below testing threshold and what you're seeing is simply what builds up over time. You could try a startup dose of metal sequerstrant to see if that removes the stains for long enough and many folks here have been getting good results using ProTeam's MetalMagic formulation. You may not need to use a lot of it so it could be a quick method for removing stains.

 

[bmtrimp]

Thanks for the advice. I appreciate it!

 

[bmtrimp]

Just wanted to follow up. I picked up some stain free (asorbic acid) and wow! It made a huge difference! Followed up with a squestrant and things are looking good. Thanks again!

 

[JoyfulNoise]

Thanks for following up. Glad you got the stains removed. Sequestrants do break down over time from chlorine oxidation and so the stains may return. You should see how long it takes for the startup dose to last and that will give you an idea of how much sequestrant you'll need for maintenance.