Are CH levels in any way associated with water color?

[three4rd]

Hi,

I'm having great trouble so far this year with the pool color being green rather than blue. My CH is around 160. I seem to recall reading somewhere that lower CH levels can be associated with water clarity / color issues, but perhaps I'm totally wrong on this. My readings are all within recommended parameters and the water is clear, just that it's not blue.

Thanks,
Keith

 

[chem geek]

No, CH won't affect the color. If the CH gets rather high, especially if pH and/or TA are high, then the pool can get cloudy, but not colored.

Water that is colored but clear is usually from metals. Iron is yellow to brown but against a blue pool surface it looks green. Copper may be green or blue-green.

If you lower the pH and the color fades, it's most likely from metals; likewise if you raise the pH and the color intensifies, it's most likely metals.

 

[three4rd]

No, CH won't affect the color. If the CH gets rather high, especially if pH and/or TA are high, then the pool can get cloudy, but not colored.

Water that is colored but clear is usually from metals. Iron is yellow to brown but against a blue pool surface it looks green. Copper may be green or blue-green.

If you lower the pH and the color fades, it's most likely from metals; likewise if you raise the pH and the color intensifies, it's most likely metals.

Hi,

I had even added a quart of stain / metal control. That is interesting about the interaction between pH and color. I will experiment a bit with that. There was improvement (less green, a bit more blue) after I cleaned out and recharged the filter. Friends of ours who had a similar problem said they just kept backwashing and brushing. This color issue is rather unprecedented in the 29 years that I've had the pool. Thanks for the info. I'll probably try lowering the pH and see what happens. Given that I already added stain control, shouldn't that have taken care of it?

Thanks,
Keith

 

[three4rd]

Curious....why does lowering or raising the pH affect color in the presence of metals? More importantly for my purposes, how do I get rid of the metals if having already added stain / metal treatment didn't already do the job? There is no reason there should be any metals present in the pool, but I can't rule anything out.

 

[chem geek]

Because the metal oxides-hydroxides precipitate more at higher pH and it is those that color the water because the concentration of metal ions by themselves is far too low to show significant color. By "precipitate", this doesn't mean just on surfaces, but as particles in suspension which is what can give the water color.

As for the metal sequestrant, that would prevent this IF there was enough of it used, but remember that chlorine breaks it down over time so you need to keep adding more.

 

[three4rd]

I'm the one who doesn't use chlorine.......biguanide system instead. The color is improving after lowering the pH, but it could also be a function of the filter just taking really long to clear up whatever is going on, since the pool has looked a bit better each day. Either way, the pH was over 8 so it needed lowering. I might add a bit more sequestrant anyway...can't hurt. Thanks for the explanation.