Stained Vinyl Liner

[Cpagasky]

No problem Tom, I have been brushing it and I'm leaning back toward my initial thoughts of this being a stain as opposed to algae. I had kept the pool at chlorine shock levels for seven days and the levels have remained since. I think there may have been some algae originally as I had some issues getting my chlorine correct early in the year due to large amounts of rain but the stain was always hiding under it. I may just live with it through the summer and try to work on it later in the year when I can lower the chlorine levels and use some stain remover. Let me know if anyone has any better ideas. Thanks

[PoolDoc]

Stains that fade -- but do not disappear -- in *liner* pools with lots of chlorine and no algae are often a result of fungus or mold growing on the DIRT side of the liner. Pigment from the growth will leach through the liner.

There's no real fix, except replacing the liner and treating the underlying surface to prevent regrowth.

[Cpagasky]

That could very well be the case, but as I said earlier I've had these stains last year as well and when I treated with oxalic acid the stain will disappear for a short time only to return a couple days later. Would that be consistent with a fungus on the backside of the liner?