Why is my water blue green?

[Vinny]

This is a question always asked.

I just happened to be glancing through my son's physics book and found the answer.

The reason, other than reflection, is that water absorbs infared light. It absorbs it quite a bit. Whenever something absorbs light we see the complimentary color which in the case of water is blue green.

Over the years I've asked this question along with others. Answers were varied but usually included metals in the water and such. Now we have the answer. I imagine this shows more in a light color tub then in a darker one (mine is a white shell).

Science is a wonderful thing!

[gwstudios]

I was going to say food coloring.

[stuart]

This is a question always asked.

I just happened to be glancing through my son's physics book and found the answer.

The reason, other than reflection, is that water absorbs infared light. It absorbs it quite a bit. Whenever something absorbs light we see the complimentary color which in the case of water is blue green.

Over the years I've asked this question along with others. Answers were varied but usually included metals in the water and such. Now we have the answer. I imagine this shows more in a light color tub then in a darker one (mine is a white shell).

Science is a wonderful thing!

Well then, we've discovered a new wonder...We can manipulate light absorption with sequestering agents or heavy oxidizers because for over 20 years I've been curing blue/green water with that!

Honestly, looking at a lagoon where the water looks blue/green and having your spa water turn to a greenish tint are two different things…Don't confuse physics and common chemistry

I also not so sure that it is "absorbed" in the way you think...the main difference is refraction vs. reflection. What we’re seeing most of the time in color changes in water is refraction dependant on the angle light come into the water and what obstacles it encounters. Sometimes those obstacles are metal particles that can reflect. Think of it like a prism….water is a good prism.

Light is really an electromagnetic radiation and radiation can be either wave or particulate energy….Light is questionable and may be both so absorption is possible.

[TubsAndCues]

One thing I've noticed over the years of caring for tubs in both my store and at home is that when your Total Alkalinity gets just a bit low and the sanitizers are at a good level, the water can have a clear but green tint to it.

I don't know exactly why this happens, but I've seen it dozens of times.  Typically I see it more in bromine tubs than biguanide and chlorine tubs, but it happens there too.

[stuart]

That's simple oxidization...Put acid on metal and you'll get a similar reaction…a blue/green tint

Low alkaline is high acid and will oxidize the metal particles in the water.

[Hillbilly Hot Tub]

Total alkalinity is the measure of the amount of alkaline buffers (primarily carbonates and bicarbonates) in your water. These alkaline substances buffer the water against sudden changes in pH. Hardness and softness of water.

We use pH as an index to express how acidic or basic a solution is. (The scientific definition of pH is “the negative logarithm of the hydrogen ion concentration”.) A pH greater than 7.0 is basic, and a pH lower than 7.0 is acidic.

Quite often I have seen low ALK and a good or high PH.