Staining caused by solar heater?

[giulietta1]

I wasn't sure what topic this went with! Chemical, water testing, structural?

I've had some mysterious staining in my pool. Several pieces of indirect evidence pointed to metals as the cause. The local pool store lady was stubborn about testing my water for metals, so I didn't actually get my water tested for metals. However, I observed a fading endpoint on the CH test, my pH had been very low (possibly causing corrosion of metal components in equipment), and vit C tablets faded the staining when dropped in the pool. So I used ascorbic-acid based stain remover and Metal Free, and the stains cleared up beautifully.

From what I have seen, tho, there is more staining stuff coming from the solar heater return! I didn't think there was any metal in that equipment, but the staining has the same properties as before, including the response to the vit C. I have actually SEEN discolored water coming from that return when I start up the booster pump (for the solar). Also it leaves a rather concentrated deposit on the step towards which it flows.

I would love some advice on this! Offhand I don't know the mfr of my solar heater/panels. I have some info on that, so I can look it up at home later. I don't recall whether I circulated water thru the solar panels while I was running the stain treatment. Maybe that would be the solution.

I am reasonably certain the metals (if that's the problem) are not coming from my source water. I suppose it's possible that some metal-contaminated water was in my solar pipes and didn't get the benefit of the treatment. It's hard to imagine that such a small volume of water could hold enough metals to cause this degree of staining, but I don't know enough to rule out that possibility. Another possibility, mentioned previously, is that there are metal components in the solar collection system which come into contact with the water.

Should I get my own metal testing kit or strips? (I really don't want to try the pool store again.) Does anyone have other ideas re: what could be causing this? My pH hasn't tested below 7.2 since I got plenty of alk in the pool, more than a month ago. I'd appreciate comments, suggestions, and/or advice.

TIA,
Jules

 

[JohnT]

Some types of panels can lose material from the panels if standing water remains in the panels while the sun is shining. Normally this is carbon black from rubber panels, but other panels may be subject to similar deterioration. I would think this would be fairly easy to remove with a brush though.

A metal test kit would certainly be worthwhile in the presence of staining problems.

 

[giulietta1]

The stains don't brush off, but I appreciate the input! I will try draining the solar when I'm not using it, to see if that will help.

Do you know the # of the Taylor test kit for metals?

 

[chem geek]

The Taylor K-1264 at this link tests for both copper and iron, but it is expensive at $84. Typically, the metals combine with the carbonate in the water and this occurs more readily under conditions of high TA and high pH (because that's when there is more carbonate in the water). Copper carbonate is blue-green and is the typical patina you find on copper that is weathered though this often includes copper hydroxide as well (copper oxide is also possible and is black). Iron carbonate is yellow-to-red-to-brown while iron oxide-hydroxide and iron hydroxide are red-brown to orange-red (the latter is more common since the chlorine in water tends to oxidize the iron to the state where it combines more readily with oxygen than with carbonate). So typically, if your stains are greenish, then it's copper while if it's rust colored then it's iron.

Regardless of which metal you have, the solution is the same. First add a sequestrant to prevent further precipitation of metal and to capture metal precipitate you will dissolve in the next step. Then, use an acidic reducing agent such as ascorbic acid (vitamin C) to remove the stain (Jack's Magic products are good stain removers as well; oxalic acid is also sometimes used) though you need to turn off the pump and have the chlorine level low or near zero (because chlorine will oxidize the ascorbic acid). The reducing agent is mostly for iron to force it into a more readily soluble form that is more easily held by the sequestrant. The only way to actually remove the metal from the water completely is through drain/refill, splash-out and backwash.

 

[giulietta1]

I found the K-1264 at the Taylor website, but did more looking and found the k-1730 ($21.05) for copper testing and the k-1716 ($52.55) for iron. Hmmm, the prices for those two individual kits add up to LESS than the cost of the combined kit! I didn't study the components closely enough to determine whether they were the same, but that pricing makes me curious.

My concern is that I've got SOMETHING that is apparently contributing metals to my pool water. I can do the stain removal/metal sequestering route again, but if possible I want to isolate the source of the metals so I can stop this happening!

I am reasonably sure that there's no metal in the source water. I've tested my tap water with the CH test and didn't have the fading endpoint problem with that water. Nor do I see any metal staining in toilets, etc.

Thx,
Jules

 

[duraleigh]

Hi, Jules,

You certainly have all the characteristics of iron stains. Something in that circulatory loop of pool water is metal. (good chance that the low pH triggered the release or certainly aggravated it) I don't know solar systems well enough to have an an educated opinion as to whether or not that could be the source. You don't possibly have an old heater still in the loop, do you?

 

[giulietta1]

Nope, no heater except the solar. There is apparently SOMETHING in there that causes the staining! Every time I start up the solar, a brown cloud issues from the return. It doesn't cloud the water all thru the pool, just settles out. . .

The previous owner of the house was a DIY-er who did some rather funky things in installing the pool. The pipes I can SEE are PVC, but I don't know what's in the solar panel tubing. I still haven't looked up the brand/mfr.

Thx,
Jules

 

[mbar]

If there is a cloud coming out of your return from the solar panels then I would think that you would have to flush out the panels. I would put in a big dose of sequestering agent - more than the amount they say on the bottle. Keep your ph at 7.0 to 7.2 and keep the pump running for 24 hours with the solar panels turned on. This way you will get the sequestering agent through the panels. You can put a piece of pantyhose on the return from the panels to collect any particles that are getting through. Keeping your ph low and using the sequestering agent will sometimes lift off stains that are new. IF this doesen't work, then you can put some ascorbic acid in again. I wouldn't buy a metal tester yet - you really don't need it. Just use the sequestering agent, and keep your ph on the low side for now and see if it helps.

 

[giulietta1]

Well, I have one dose of Metal Free left. Maybe that would be enough??

If there are metal deposits inside the pipes I should think your method would work. . . don't know if the stocking would help (the particles are very small). Worth a try, I suppose.

Thx,
Jules

 

[Poolsean]

Have you considered your booster pump? There may be metals in it, such as diffuser screws and shaft seal and spring. With low pH, this will cause corrosion.
Can't think of anything in the solar system that would cause a metallic staining.
Did you say you tested your source water for metals? Well water will sometimes have metals. Left sitting in a solar system that was isolate can allow it to settle and come out in a more concentrated cloud when the solar is turned on.

What type of valves are you using to isolate the solar panels? Brass gate valves can be affected by low pH too.

 

[mbar]

I would go ahead and put another dose of metal free in. I think that if it doesn't clear up after the whole system is flushed, then it is coming from somewhere that is bleeding out metal, as sSean said. After you have the ph balanced and the system is flushed, and you still get brown water out of the solar heat, then I can't think of what is causeing it from the solar panels. Did you check to see that the solar panels are not pushing water out from the pump? It is only a thought that the lines were swithed, and instead of getting the water throught the pump to the solar panels and then to the pool, it is going from the pool to the solar panels, into the pump then returned to the pool, whcih could give you discolored water.

 

[giulietta1]

My pH isn't low--it's been pretty close to perfect, around the 7.4-7.5 range. It WAS low for some time, but it's been at appropriate levels for a couple of months.

I don't have a metal test (yet), but I have other evidence that there's little or no metal in my source water (not well water). No metal stains in toilets/showers/etc; no fading endpoint on CH test. When I test the pool water's CH, I get the fading endpoint problem.

No, the lines aren't switched; the return pipe is exposed and the water exits that, doesn't enter it. That I can say with certainty. The booster pump is on the return line from the main pump and filter.

I'm not sure about the valves, but I think everything is PVC. Actually I don't open or close any valves to start up the solar, I just turn on the booster pump. There is a valve to isolate it, but I don't usually do anything with that.

I will try another dose of Metal Free, with the solar running this time.

Thx,
Jules

 

[giulietta1]

I got a strips-based test kit for iron and copper; apparently I do have copper! Somewhere between 2 and 3 ppm. Iron test looked to be zero. I will put in the dose of Metal Free this weekend while I'm home to keep an eye on the pool.

Thx,
Jules

 

[mbar]

I wonder if there are any copper pipes or couplings in the plumbing for the solar heat? Did you test your fill water? It would be good to know where the copper is coming from. Even if you don't find out, you can control the metals by keeping metal free in the water and keeping your chlorine in the proper range so that you won't have to shock your water, which is one of the reasons the metals fall out of solution. I can help you manage water with metals in it, so don't let it get you down!

 

[giulietta1]

I don't know about any copper pipes or couplings in the solar apparatus; my understanding was that they didn't usually have them. What I can see is all PVC, but I'm guessing there must be some copper in there somewhere!

Sooo. . . I don't have to shock if I keep my chlorine in the proper ranges? What about KPMS shock? Does that also cause metals to fall out of solution?

I haven't tested my source water YET, but will do so soon, tonight probably.

Thanks so much for your help!

Jules

 

[duraleigh]

Hi, Jules,

Okay, time to show that despite my ignorance, I never lack opinions!! :lol:

I think I remember reading that copper will precipitate out in a greenish cast.....not brown like you described. If that's correct, and you dont have iron as the source, could it be organic? (dead algae). Again, your description was classic for iron stains.....I would have doubts about copper.

 

[mbar]

duraleigh is right, copper usually gives a bluish stain. The fact that the brown only comes out when you use the solar would say that is coming from there, so it may be something that is still being flushed out. All the same you can take your chlorine up to shock levels slowly, while keeping an eye out for any stain starting to form. If you see stain starting, then you can add more sequestering agent, while bringing your ph down to 7.0-7.2. As for KPMS, I am not familiar with it - I don't know if it causes metals to precipitate or not, so I can't say - but if anyone else knows about how it works with metals I would love to hear. In the time I have been dealing with metals in my water, I have never been told to use this so as not to get stains. It would be wonderful if it works! Anyway, you never have to shock your pool water if you don't have any combined chlorine. Shocking is used to reach the breakpoint to get rid of the combined chlorine. In most cases if you keep your chlorine steady with your cya, your chlorine should be able to breakdown organics before they can overtake the chlorine demand and you won't get any cc. Sometimes heavy bathing loads (little kids peeing) or bad storms can overtake the chlorine and then you would have to shock. Hope you find out what is causeing the brown water. The fact that it does stain, and the stain comes off with ascorbic acid makes still think it is metals. If it were organic the stains would come off with chlorine.

 

[giulietta1]

The staining itself is sort of a greenish brown. The water is clear, it just looks like a dust cloud that issues from the solar return. Then that stuff settles out. Maybe I should try to catch a sample right from that brown cloud!

KPMS is potassium monopersulfate, aka MPS, Oxone, or non-chlorine shock. Maybe you know it by one of those other names?

I don't use CYA b/c mine is an indoor pool. For the same reason leaves and such are not much of an issue. I get a few bugs, mostly a lot of dead pillbugs. Unfortunately I have persistent CC's at around 0.6 but chlorine shocking doesn't help with those (again b/c of the indoor pool and lack of direct sunlight).

It's hard to imagine that there's something in the plumbing of the solar collectors that hasn't gotten flushed out by the hundreds of hours I've been running water thru it!!

I really can't imagine that it could be algae, not with the chlorine levels I'd been running during the conversion from the dreaded Baq. Some of the stains look more gray or black; they look like scorch marks to me. Did you ever shoot off fireworks off a sidewalk or driveway, and they left sooty stains behind? I have some stains that look like that. But most of the staining is sort of brownish, maybe a greenish brown, and it covers most of the submerged surface of the pool. It's worse near that solar return.

I will see if I can track down more info about the solar collectors I have, and I will try the stain remover and sequestrant again this weekend.

Thx,
Jules

 

[mbar]

Can you put a piece of stocking over the return from the solar heater? Maybe you can catch some of the stuff coming out if it. It really is a mystery - why would the cloud only come out of the solar return, and not out of the regular return? It leads me to beleive that is has to be something in the solar system or pipes leading up to it or down from it. I wouldn't do the stain treatment until the cloud stops coming out - because the ascorbic acid will only lift the stain off the pool and get it back into solution, and unless there is enough sequestering agent in the water to bind with the metals, the metals will only fall out of solution onto the surface of the pool again.t The sequestering agent will bind with the metals, therefore I would just get more sequestering agent in it with the ph at 7.0. Once you have all of the "cloud" stopped, then you can deal with the surface stains. Is this the first time you have stains in the pool? Fiberglass pools tend to stain very easily, I read somewhere that it is because it has a negative charge. I don't know if I believe it, but I do know that fiberglass does stain easier than other pool surfaces. I now understand that it is an indoor pool, I missed that before. I really hope you keep posting, because I am really interested in what is going on. Would it be expensive for you to do a couple of drain and refills after the cloud stops? I am just trying to figure out the best way to get the pool stain free. I know how to get the stains off - but unless we can figure out why they are getting there, we can't keep it stain free.

 

[Guest]

sounds like biguanide residue in the collectors to me. When the chlorine hits it it changes color just like in a conversion.