Copper in the Water

[Jesster444]

I have a well that collects ground water near my pool (I think the ground water might come from a natural spring). I would like to use this water to refill any evaporated water instead of from the hose (which has municipal water). Although the water coming from the well appears clear (and is being run through its own cartridge filter before hitting the pool), my pool starts to turn green the more water that dumps in from the well. My initial reaction was that it was algae, SLAMing didn't seem to do the trick, so I looked at this forum and I started thinking it was copper. However, I read this: Copper in Pool Water - Further Reading, which suggested that copper rarely comes from ground water. I tried one of those water test kits from Lowes on the water coming out of the well and it showed nothing for iron or copper (ran the test twice and same results for both).

I talked to a water tech at a water filtration company, he thought it might be tannins and suggested I run a little test, which I ran as shown in the picture below:


From the left:

1. Tap water
2. Tap water with a capful of 7.5% bleach
3. Well water
4. Well water with a capful of 7.5% bleach
5. Well water with .3oz of dichlor

The color change was pretty instant (within 5 minutes). To me that seems like what people describe as copper reacting to the chlorine, but why are the copper tests turning out negative then? Any thoughts or other tests you would like me to run to figure this out, please let me know. Thanks!

 

[ajw22]

@JoyfulNoise likes these type of science experiments.

 

[Jesster444]

Here is how they look 2 hours later:



The well with bleach (4th from the left) has turned less green and formed some white stuff on the bottom (pictured below) and the well with dichlor has turned brown.

 

[JamesW]

Probably iron.

 

[JoyfulNoise]

That’s not copper. It’s called “natural organic matter” (NOM). What you’re seeing is the reaction of a very high dose of chlorine (a cap full of bleach in that low volume of water is literally over 1000ppm FC) with NOM causing oxidation, color formation and coagulation of the resulting by-products. This is why water treatment facilities use a lot filtration and coagulation processes to remove NOM prior to any chemical treatment processes. Otherwise you get significant fouling of the equipment and formation of disinfection by-products (DBP’s) and trihalomethane’s (THM’s) all of which are very bad for potable water.

 

[Jesster444]

So is it safe to use the well with this NOM to add back what is lost due to evaporation or will it cause me more issues than it’s worth? Is there a way to capture or filter the NOM before I put it in the pool?

 

[JoyfulNoise]

I didn’t quite follow you on your water sources - are you saying you have both municipal water and well water?

 

[Jesster444]

I have both. The well captures water that was running under the pool during construction and pumps to the nearby lake. It goes off about every 5-10 minutes and outputs about 30 gallons. With the waterfall, I get more evaporation so I thought it’d be nice to use that periodically to offset the evaporation and lower my water bill but not if it is going to cost me more in other areas.

 

[JamesW]

I would just use the better city water.

Whatever is in the well water is not worth dealing with.

There's probably a mixture of iron and other contaminants in the well water.

 

[Jesster444]

Thank you for all the information so far! The iron tests were negative and filtering out the NOMs might be a cost saving in the end based on the increased water bill. But if it takes commercial grade equipment to do so, then maybe not.

 

[JamesW]

There's probably iron in the water regardless of what the tests say.

If water comes out of the ground, there is iron in it.

 

[JamesW]

Well Water Testing - Private Well Users

www2.illinois.gov

Maybe have the water tested by a certified lab.

https://www2.illinois.gov/epa/Documents/iepa/certification-training/labs/accredited-labs-condensed.pdf