Copper(?) mystery... need advice

[ECEGatorTuro]

Hi! Looking for advice to understand if I'm doing anything incorrectly. A little background...

We live in the Phoenix area and we have a pool that completed build in Aug. 2020. Over the course of the last 2+ years, I've done all of my own maintenance and kept the water chemistry in balance. I monitor our pool frequently and the water has always been prestine (with the exception of a major dust storm or three). We have a SWG and I never use shock products or tabs, only liquid chlorine if necessary (exception to tab usage is when our SWG died prematurely towards the end of summer and needed a quick stop gap for a few weeks until replacement). Due to the SWG, our pH rises constantly so it's always a battle to keep it in check but not surprising. Our fill water is no better since it usually comes out of the tap at about pH of 8. Since our fill water has high calcium content, our CH has also increased over the last two years and the last reading was about 1400 ppm. I know that's high but I mainly monitor to keep my CSI in check so I never suffer the scaling effects that so many people in Phoenix have issues with. All that to say that the pool water never has an issue going acidic... it is always high so I generally fight to keep calcium scaling and I'm never concerned with etching issues.

That being said, our builder had to drain our pool yesterday for a repair to fix a rusting rebar stain. Once I drained the pool, I immediately noticed that there is a general blusish-green cast over many parts of the pebble plaster surfaces. It was widespread and almost blotchy in some spots. You can't really see it much when the pool is filled because we have a very light/white color pebble and the blueish-green blends in with the water. The difference is very noticible in the repair patch since it's white compared to the surrounding pebble. The tech said that it's very likely the copper is being etched away from the heater core due to acidic conditions and depositing itself on the pebble. This is where I scratch my head in disbelief because I KNOW for a fact that my water never drops below pH 7. I'm constantly battling to control rising pH, not falling!

I'm out of ideas as to where the copper came or is coming from. Our town water quality reports that the copper in the water is 0.17 ppm so it can't be the fill water. Any ideas? I'm just worried that our heater core is somehow disintegrating for some reason.

Thanks in advance for your help!

 

[AQUA~HOLICS]

Have you ever added any liquid algaecides in your maintenance routine?

 

[JoyfulNoise]

It’s not your heater unless you’re running your pool pump at very high flow rates all the time. You can verify it’s not the heater by removing the header/manifold and inspecting the copper tubes to look for erosion. You’ll need to replace all the seals though if you do remove it.

0.17 ppm copper is actually not that great for water unless that value is an average of all test wells and most of the wells are not showing any copper. You also have to realize that contaminants in fill water INCREASE over time just like your calcium hardness does. So if your CH tripled over 2 years, then any copper on the fill water triples as well.

But here’s the thing … what looks like “copper” is often not and, honestly, your pictures are not that striking. PebbleTec plaster can change color with age. My “Caribbean Blue” pebbletec turned into Caribbean grey PebbleTec a few years after installation.

Test a small area. Crush up some vitamin c in a sock and put it on a test area (while water is in the pool) and let it sit for 10-15mins. If it gets lighter in color it’s likely iron stains. If it gets darker colored, then it’s possibly copper.

 

[PoolStored]

Due to the SWG, our pH rises constantly so it's always a battle to keep it in check but not surprising.

This is a myth. What is your TA? Do you know the TA of your fill water? Reducing your TA to 60-80 will slow your pH rise.
Do you know the TA of your fill water? Do you have an autofill? Any idea on how much you lose to evaporation a month?
Do you have water features? (couldn't tell from pic) Running your water features will cause pH to rise.

A quick read...

PH TA Relationship - Further Reading

www.troublefreepool.com

Managing pH and Total Alkalinity - Further Reading

www.troublefreepool.com

 

[ECEGatorTuro]

Have you ever added any liquid algaecides in your maintenance routine?

Never.

It’s not your heater unless you’re running your pool pump at very high flow rates all the time. You can verify it’s not the heater by removing the header/manifold and inspecting the copper tubes to look for erosion. You’ll need to replace all the seals though if you do remove it.

0.17 ppm copper is actually not that great for water unless that value is an average of all test wells and most of the wells are not showing any copper. You also have to realize that contaminants in fill water INCREASE over time just like your calcium hardness does. So if your CH tripled over 2 years, then any copper on the fill water triples as well.

But here’s the thing … what looks like “copper” is often not and, honestly, your pictures are not that striking. PebbleTec plaster can change color with age. My “Caribbean Blue” pebbletec turned into Caribbean grey PebbleTec a few years after installation.

Test a small area. Crush up some vitamin c in a sock and put it on a test area (while water is in the pool) and let it sit for 10-15mins. If it gets lighter in color it’s likely iron stains. If it gets darker colored, then it’s possibly copper.

I'd rather not open the heater since it's still under warranty. How high of a flow rate would cause that? It runs about 3-4 hours/day at 60 GPM for cleaning and the rest of the time it's 20-30 GPM.

Regarding the copper in the fill water, the 0.17 ppm value is the 90th percentile of measurements according to the water quality report so it sounds like the majority of sources are lower than that (if they have any at all).

Perhaps the pictures don't give it justice but it's definitely a blueish-green cast all over the place and blotchy in some sections. Iron would make brownish stains no? In the wide angle picture, you can actually see the rust stain they just repaired (due to rebar piece sticking very close to the plaster). I can try that test and see what happens.

This is a myth. What is your TA? Do you know the TA of your fill water? Reducing your TA to 60-80 will slow your pH rise.
Do you know the TA of your fill water? Do you have an autofill? Any idea on how much you lose to evaporation a month?
Do you have water features? (couldn't tell from pic) Running your water features will cause pH to rise.

A quick read...

PH TA Relationship - Further Reading

www.troublefreepool.com

Managing pH and Total Alkalinity - Further Reading

www.troublefreepool.com

What is a myth? That a SWG increases pH? I disagree with you there. I would say that it's a component of pH rise, not necessarily the sole reason. I don't know the TA of the fill water (I haven't tested it in a long time) but my average TA over the past year is 70 according to my logs. I have an autofill but I don't know how much evap occurs (I've never measured). The only water feature we have is the pour over from the spa into the pool so it's some minor aeration but not a huge amount. It's part of the normal water circulation flow as the pop-up cleaners shift zones so I can't shut it off. I guess the point I was trying to make to the repair tech was that my pool never goes below a pH of 7 unless I intentionally dose enough acid so there is no way copper could be leaching from the heater. My pool likes to settle around 8.0-8.1 pH if I ignore it for a week. In the summer, I will dose enough acid to get to pH 7.2 and within a week it will be a pH 8.0. Is that a normal rate of rise for pH for most pool owners? I have no idea. I'm fairly "new" to this since the pool is only a little over two years old.

 

[JoyfulNoise]

Those flow rates generally aren’t excessive. It would probably be a good idea to take the heater out of the plumbing when the cleaners are running by using a bypass configuration but that would require valve actuators and an automation system. You don’t have any equipment or pool details listed in a signature so it’s not as easy to help you without knowing specifics.

The copper in the municipal water report sounds immaterial as well. Copper is rare to find in ground water supplies as it usually come a from a source of contamination rather than natural occurrence.

Looks can be deceiving. Iron stains, depending on their extents and thinkness don’t always look “brown” like rust. And, with a colored plaster as the background, a faint iron stain could look greenish.

The easiest way to get more information is to do the Vitamin C test. That will tell you if copper is there or not.

 

[proavia]

Chances are the fill water TA is 110-130 and pH 7.7-8.0
With our high evaporation rate in the Chandler/Gilbert area, will require a bit more work to keep the TA in check. Shoot for a TA of 60 as that will help slow the pH rise.

SWG does not cause the pH to rise. Many pool owners use tabs prior to installing a SWG. Tabs are acidic and help keep pH in check (while increasing the CYA to unacceptable levels). Remove the tabs from the equation and the pH will rise - with or without a SWG.

CH of the fill water is also an issue. Your fill water will probably average 225-250 of CH.
With a CH of 1400, what have you been keeping the pH and TA at?
CH 1400 is mostly unmanagable without agressively keeping the pH and TA in check - agressively managing the CSI. CSI should be kept slightly negative - between 0.00 and -0.30 - for pools with a SWG.

Post a full set of current test results - your last ones since the pool is empty now.
Post your fill water pH, TA and CH.

Are you using PoolMath?
Following TFP recommended levels?
Using the FC/CYA Levels?
Any chance of a water softener in your near future - and plumbed to your autofill line - to help keep CH in check?

Fill out your signature with pool, pool equipment (including manufacturer and model number) and test kit info?
This assists us in providing help more tailored for your pool.

https://www.troublefreepool.com/account/signature

 

[PoolStored]

my average TA over the past year is 70

My pool likes to settle around 8.0-8.1 pH if I ignore it for a week. In the summer

Yes, that is typical. Higher TA and lower pH are the major drivers of pH rise. Aeration will cause pH rise. Solar cover will reduce pH rise. It's all about outgassing CO2. Couple good reads:

Managing pH and Total Alkalinity - Further Reading

www.troublefreepool.com

PH TA Relationship - Further Reading

www.troublefreepool.com

To raise the pH of 10,000 gallons of pool water from 7.5 to 7.8 (CYA 30ppm, TA 100ppm, zero borates), you need to liberate about 0.3lbs of CO2 gas. 1lb of CO2 gas occupies 243 liters or 64 gallons of volumetric space at standard atmospheric pressure and temperature; so 0.3 lbs of CO2 would be equivalent to 19.2 gallons. So, even if all of those bubbles coming out of your return line are 100% CO2 (which they are most certainly not), you do not have > or even = 19 gallons of gas coming out of your pipes, let alone what it would take for it to rise from 7.2 to 8.

Aeration caused by the SWG is not a major contributor to pH rise. Yes, the aeration does cause some pH rise but you would be hard pressed to see it without some very specific equipment capable of measuring small changes in pH. The water coming out of the returns will generally have higher pH as is predicted by the electrolysis equations for the conversion of chloride to chlorine but, by and large, all of that pH rise will eventually go back down once the chlorine has oxidized organics or killed pathogens as those reactions are acidic (lower pH).

As @proavia hints, you have constant pH rise because you have high fill TA and are constantly fighting pH rise because of the TA. I too have an SWCG. I added acid at the beginning of the year to adjust after winter, and a bit to winterize. I added 0 MA during the pool year and my pH sat at 7.4. My TA is 60. I don't have to fill, typically I have to drain from rain. You may be able to get to a fairly stable pH below 8, if you monitor and maintain TA at 60 with muriatic and aeration. Even your pH of 8-8.1 is ok...no reason to drive it down to 7.2, unless you are trying to lower TA.

Hope this helps!

 

[mgtfp]

Even your pH of 8-8.1 is ok...no reason to drive it down to 7.2, unless you are trying to lower TA.

Apart from the high CH of 1400. That requires indeed some aggressive pH/TA management as mentioned by proavia to keep CSI in check, especially with an SWG.

Ultimately, that CH needs to come down. This will allow maintaining pH in a region where CO2 outgassing slows down.

 

[ECEGatorTuro]

Those flow rates generally aren’t excessive. It would probably be a good idea to take the heater out of the plumbing when the cleaners are running by using a bypass configuration but that would require valve actuators and an automation system. You don’t have any equipment or pool details listed in a signature so it’s not as easy to help you without knowing specifics.

The copper in the municipal water report sounds immaterial as well. Copper is rare to find in ground water supplies as it usually come a from a source of contamination rather than natural occurrence.

Looks can be deceiving. Iron stains, depending on their extents and thinkness don’t always look “brown” like rust. And, with a colored plaster as the background, a faint iron stain could look greenish.

The easiest way to get more information is to do the Vitamin C test. That will tell you if copper is there or not.

Thanks for the tip! I'll try the vitamin C test when I can get my hands on it.

Chances are the fill water TA is 110-130 and pH 7.7-8.0
With our high evaporation rate in the Chandler/Gilbert area, will require a bit more work to keep the TA in check. Shoot for a TA of 60 as that will help slow the pH rise.

SWG does not cause the pH to rise. Many pool owners use tabs prior to installing a SWG. Tabs are acidic and help keep pH in check (while increasing the CYA to unacceptable levels). Remove the tabs from the equation and the pH will rise - with or without a SWG.

CH of the fill water is also an issue. Your fill water will probably average 225-250 of CH.
With a CH of 1400, what have you been keeping the pH and TA at?
CH 1400 is mostly unmanagable without agressively keeping the pH and TA in check - agressively managing the CSI. CSI should be kept slightly negative - between 0.00 and -0.30 - for pools with a SWG.

Post a full set of current test results - your last ones since the pool is empty now.
Post your fill water pH, TA and CH.

Are you using PoolMath?
Following TFP recommended levels?
Using the FC/CYA Levels?
Any chance of a water softener in your near future - and plumbed to your autofill line - to help keep CH in check?

Fill out your signature with pool, pool equipment (including manufacturer and model number) and test kit info?
This assists us in providing help more tailored for your pool.

https://www.troublefreepool.com/account/signature

I always thought that SWG do contribute to pH rise due to the electrolysis process but PoolStored seems to have answered the reasons as to why that's not the case. Interesting.

I just refilled the pool last night and just tested the water this morning. You're right about the CH in the fill water (we're neighbors!) as I got 250-300 on this test. When I had the CH at 1400, my TA was roughly in the 70-90 range and I would constantly have to add MA 1-2 a week to keep it from drifting to its happy place (around pH 8.1). I was aggresively managing the CSI and trying to keep it bouncing between -0.3 and 0.3 which is probably why after 2+ years, I have an almost impercetable calcium scale line starting to show.

My last test result before the full drain was:
FC - 5
pH - 7.8
TA - 70
CH - 1350
CYA - 50
Salt - 4000
Borates - 50

Current test results with a fresh fill:
FC - 0.5
pH - 8.2
TA - 140
CH - 300
CYA - 0
Salt - 400
Borates - 0

I've been using PoolMath for several years now (my first foray into pool care was a little 12' AG pool I would put up every summer) and I love it. I try to stay within the recommended values and just make certain compenstations to keep CSI in check due to the high CH. We have a softener for our house but I never though about plumbing it to the auto-fill. That's not a bad idea! I'd just have to figure out how to tie into our current soft water loop in the house or perhaps buy a separate system just for the pool autofill. What do people typically do?

I just added all of my info to the signautre. Thanks for pointing that out! Thanks for all of your help too.

Yes, that is typical. Higher TA and lower pH are the major drivers of pH rise. Aeration will cause pH rise. Solar cover will reduce pH rise. It's all about outgassing CO2. Couple good reads:

Managing pH and Total Alkalinity - Further Reading

www.troublefreepool.com

PH TA Relationship - Further Reading

www.troublefreepool.com

To raise the pH of 10,000 gallons of pool water from 7.5 to 7.8 (CYA 30ppm, TA 100ppm, zero borates), you need to liberate about 0.3lbs of CO2 gas. 1lb of CO2 gas occupies 243 liters or 64 gallons of volumetric space at standard atmospheric pressure and temperature; so 0.3 lbs of CO2 would be equivalent to 19.2 gallons. So, even if all of those bubbles coming out of your return line are 100% CO2 (which they are most certainly not), you do not have > or even = 19 gallons of gas coming out of your pipes, let alone what it would take for it to rise from 7.2 to 8.

Aeration caused by the SWG is not a major contributor to pH rise. Yes, the aeration does cause some pH rise but you would be hard pressed to see it without some very specific equipment capable of measuring small changes in pH. The water coming out of the returns will generally have higher pH as is predicted by the electrolysis equations for the conversion of chloride to chlorine but, by and large, all of that pH rise will eventually go back down once the chlorine has oxidized organics or killed pathogens as those reactions are acidic (lower pH).

As @proavia hints, you have constant pH rise because you have high fill TA and are constantly fighting pH rise because of the TA. I too have an SWCG. I added acid at the beginning of the year to adjust after winter, and a bit to winterize. I added 0 MA during the pool year and my pH sat at 7.4. My TA is 60. I don't have to fill, typically I have to drain from rain. You may be able to get to a fairly stable pH below 8, if you monitor and maintain TA at 60 with muriatic and aeration. Even your pH of 8-8.1 is ok...no reason to drive it down to 7.2, unless you are trying to lower TA.

Hope this helps!

Thanks for the explanation!

Apart from the high CH of 1400. That requires indeed some aggressive pH/TA management as mentioned by proavia to keep CSI in check, especially with an SWG.

Ultimately, that CH needs to come down. This will allow maintaining pH in a region where CO2 outgassing slows down.

Yeah, I had to aggressively manage the pH rise with my CH being so high. It's a moot point now since I had to drain it and just refilled it again. It's nice to have the CH back to 250-300!

 

[proavia]

Plumbing soft water to the autofill - with our hard water, this would be a good thing.

My garage and pool are on the same side of the house. I drilled a hole thru the exterior wall of the garage for the soft water line, installed a backflow preventer on the outside garage wall, ran the soft water line down the side of the house and plumbed into the autofill line. I used 3/4" copper above ground and changed to sched 40 PVC underground.

My neighbor had to run PEX from the softener in the garage, up thru the attic space to the opposite corner of his house. Where the PEX comes out under the eave, he converted to PVC, ran it down the wall into the ground and connected to his autofill. Any PEX exposed under the eage and the exposed PVC was painted to match the house and protect the PEX/PVC from the sun (this is important).

Since connecting my autofill to soft water 2 years afo, my CH has risen by 50 ppm - and some of that could be testing error. Before this, my CH would rise about 300-500 ppm per year due to our high evaporation rates here in the desert southwest.

Keeping the TA in the 60-70 range has lessened my pH rise, even with a SWG. keeping CSI in the 0.00 to -0.30 (negative 0.30) range has kept the SWG plates clean. Some here have never had to clean their SWG as they also keep the CSI within that range.

EDITED TO ADD - any PEX run thru a wall cavity or the attic is a continuous run without joints or connections. Probably not a good idea to have joints/connections/couplers anywhere in the attic/walls.

 

[onBalance]

Sorry to be so late responding to this issue, but in regards to your copper staining problem, there is a possible reason for this to occur. Even though the city water does not contain a lot of copper, the water coming out of your backyard faucet may contain a significant amount of copper. And that is because some houses have copper plumbing throughout and if that plumbing is not properly grounded, copper can jump off the pipe at the faucet and build up in your pool water.
You should have that backyard faucet water tested for copper to determine if that is what is occurring.

This issue is exactly what happened to a pool in my area many years ago. I tested the water in the front of house and no copper was found, which confirmed the city water report. Then I tested the water at the backyard faucet and it contain a lot of copper. I hired a plumber to check the house plumbing, which had copper piping, and he found some aluminum bonding fittings that were loose. He changed them to copper fittings and made them very tight. Problem corrected. Drained pool, performed acid wash, and re-filled with copper free water.

If your house does not have copper piping or is properly grounded, and the backyard faucet water doesn't contain copper, then I am at a loss and do not have an answer for this problem. Based on your photos, it does appear to be copper staining.