Copper Piping Failure

[SherrySt]

Is it truly possible that the copper piping inside a pool heater can corrode from the Alkalinity being too low? If so, how long would it have to be low and what would the number have to be? Thanks!

[waterbear]

Low pH is the biggest factor in copper heat exchangers corroding. Low ALK does often tend to go hand in hand with low pH. If you pH is staying stable and not below 7.2-7.4 and you alk is only slightly low I would not worry too much about it. If your alk is low and you cannot get your pH to remain fairly stable then I would adjust the alk.

[waste]

Sherry, welcome to the forum! As I understand it, low alkalinity, in and of itself, doesn't corrode metals, it's acidic (<7.0) water that eats them up. However, the alkalinity is a buffer that keeps the pH from fluctuating too much, almost every time I've had to replace a heat exchanger (3 -4 a year) the pH was very far below my test kit's ability to read and the alk was also low if not nonexistant. The 2 do play off of each other, but it's acidic water that eats the copper heat exchangers. In every case that I've had to replace a heat exchanger, it's because the pool owner has a 'set and forget' tri-chlor feeder, and hasn't taken the time to test their water (once a week would have given them an indication that there was a problem), so they have high cl (and cya) and LOW pH, a very bad combo for metals like copper. As CarlD says 'keep ahead of your water; 2 - 5 min a day to test' - it's probably the BEST advice that is regularly seen on this forum!
I know a fair bit about pool chemistry but there are folks here that truely 'know' chemistry, I'll leave it to one of them to refute or amend what I've said.

EDIT: Evan beat me to the send button

[waterbear]

And I concur with everything you said!:D

[SherrySt]

Thank you so much for your replies. What would the proper steps be to correct the problem? Would there now be copper in the water? If so, how do I remove it?

[waste]

Sherry, to correct the problem, keep your pH above 7.0 (7.0 is neutral and won't hurt anything) though keeping the water slightly 'basic' (ie 7.2 - 7.8) is prefered. You can raise the alk and pH by adding baking soda (it will raise the alk a good bit and the pH a little) There are some expensive products available from your neighborhood pool store, but I'd suggest using the ones recommended here, that you can buy at the supermarket.
(EDIT) Sherry, mbar, knows more about this than I, but some sort of sequestering agent should keep the liberated copper from staining your pool.

Evan, thanks for the 'back-up', you are a credit to this forum!

[waterbear]

It would not hurt to have your water tested for copper and then post the test results (Not just the copper but a full set of results for FC, TC, pH, ALK, Calcium, and CYA...if they can do it an iron test would not hurt either). We can then advise you better on what to do.

[SherrySt]

I do have Ben's test kit so I can post those numbers, but I will have to get the pool store to test for the minerals in the water. I will post them tomorrow. It is raining REALLY HARD here!

[SherrySt]

I have the readings on the pool, using Ben's PS234 Kit. The pool is 22,000 gallons, inground, vinyl liner.

FC .5
CC 0
TC .5
pH >6.8 (color was lighter than lightest color0
Alk 150
Cal 550
CYA The dot disappeared as soon as I started pouring water into the tube.

The heat exhanger in the heater has apparently corroded completely thru. The pool stores says it's due to low pH and has recommended adding pH Up. There is also an automatic chlorinator on the pool.

Thanks for any help anyone can give me!!

[duraleigh]

Hi, Sherry,

You have some pretty important water quality issues.....most of which probably center around the use of the inline-chlorinator.

I would do two things immediately. First, bring your chlorine level up to at least 15ppm and maintain it above ten the rest of the swimming season. Do this with Clorox only. Secondly, get some 20 mule team Borax and get your pH up.....shoot for 7.4.

You've got a lot of adjustments to make but I would suggest those two right away. There's more to come but by keeping things pretty simple right now I think it will keep you from being overwhelmed.

Lastly, don't use any more pucks....they're causing most of your problems.

[SherrySt]

Thanks, Dave! Before I add the bleach I have another question. . .The pool store tested for metals and said that the copper is at 10 and the iron is at 6.6. They said to add 10 bottles of Omni (sequestoring stuff?!?). They also said not to add chlorine again until the metals were down. When the chlorine was added previously, the pool immediately turned green. I assume that was a reaction to the Omni stuff? Anyway, should the water be tested for metals again or should I go ahead and get the chlorine and pH where they belong. THANK YOU!!

[duraleigh]

Sherry, you've got a multitude of issues with your pool water. Those metal results seem pretty high. I would give serious thought to a drain and refill at this point.

Adding the sequestrant prior to the chlorine is a good idea (mbar or other metal "specialists" can advise you better than I) but I'm not so sure that the cost and hassle of the sequestrant, all the clorox, borax, then probably having to aerate to get your Alk down will make it more cost-attractive to start with new water.

You'll have to make the decision but I think, if it were my pool, I'd make a fresh start.....you'll be swimming in a lot less time.

[SherrySt]

Dave - I have been thinking the same thing. With the expense of fixing the heater (it was hard piped for the water to go thru the filter/pump then into the heater) and the cost of the chemicals, it may be worth a drain/refill. If I would go that route, would you recommend a complete drain or only partial? We are in Western PA and I don't want the liner to "float" if we do a complete refill and cause more problems. Is there a magic number that is safe to drain to before you destroy your liner?

[duraleigh]

Sherry,

You might be a candidate for the "plastic sheet method" that's been mentioned on this forum several times but I'm not sure anyone has actually tried it.

Basically, buy enough 4 mil poly sheeting to make a 36' dia circle. (width of your pool plus 4' on each side for the depth. You'll have to tape smaller pieces together (duct tape) to form this piece.

Lay the piece on top of your pool and begin draining. As the water goes down, add the new fill water on top of the plastic at the same rate you are draining the old water from underneath.

The plastic separates the two bodies of water (perhaps not perfectly, but close enough) and, when it reaches the bottom, you have done a complete refil without reducing the total volume in your pool at any time.

Again, it's a great idea and I see no reason why it wouldn't work.....just don't think anyone on the forum has actually done it. If they have, maybe they'll chime in and report results.

[waterbear]

Thanks, Dave! Before I add the bleach I have another question. . .The pool store tested for metals and said that the copper is at 10 and the iron is at 6.6. They said to add 10 bottles of Omni (sequestoring stuff?!?). They also said not to add chlorine again until the metals were down. When the chlorine was added previously, the pool immediately turned green. I assume that was a reaction to the Omni stuff? Anyway, should the water be tested for metals again or should I go ahead and get the chlorine and pH where they belong. THANK YOU!!
I would drain and refill...your copper levels are through the roof and so is your iron. Sequesterant will not remove the metals...just make them unreactive with chlorine for a time and then your problems will return unless you keep adding sequesterant. In the long run draining will be your least expensive option! Stop the trichlor...that is what caused the problem in the first place (actually, not keeping tabs on your pH caused the problem with the low pH but your CYA levels are also very high). The plastic sheet method is probably your best bet. If you add chlorine now your water will turn green as the chlorine oxidizes the copper in the water.

[JohnT]

You'll have to tape smaller pieces together (duct tape) to form this piece.


You can buy large pieces of plastic from greenhouse supply places that will be big enough with no patching. We used to have above ground tanks at work that were drained and refilled this way, and it does work. Ladders etc. might have to come out.