pH and liner bubbles

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nagrath

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May 12, 2012
16
Ok, I'm freaking out. I finally got through my CYA-Ammonia-superchlorination drama on my 16x34 5-year-old inground vinly pool, gotten all the numbers good, pool sparkling, and a couple of days ago I noticed a few bubbles in the liner. Small, low, barely noticeable. Today I looked, and either there are a lot more, or the light made them very visible. They seem to be everywhere, in no discernable pattern. just evenly distrubuted about the pool, even on sides and in the deep end. What's going on? I have had trouble keeping the pH high enough but this year it was actually high (7.8 plus on the taylor) until I lowered it and super-duper-chlorinated to remove the ammonia created over the winter by CYA conversion, However now, my Taylor test says my pH is 7.2, pool co test says 7.8, and my liner is bubbling. Doe this mean I have to get a new liner? I did have to add around 40 gallons of chlorine to superchlorinate, but my FC was never above 10 or so! Can super high chloramine levels damage the liner, too? Anyone know what replacing a liner of that size costs and involves? Help!!!

John
 
As I said in my post, it is an in-ground pool. I am getting soft "blisters" in the liner, maybe 6-8" long, 3-4" wide, pretty evenly distributed about the pool. I will try to post a picture later. they are soft, and give the bottom a "squishy" feel under the toes. I am guessing that water is somehow able to diffuse through the liner; while we did have one set of wrinkles due to a watertable rise once, that was a single radiating set of narrow ridges, these are evenly distributed soft blisters or bubbles in the liner.

John
 
The water will not penetrate the liner. The most common cause of the liner coming away from the wall is water table issues (ground water behind the liner). However, that doesn't sound like your issue since you have "bubbles on the floor. A good pic would be helpful and a current set of test results (particularly pH) may be very helpful.
 
Thanks, I will try to get a full set of test results and some pictures later today. Last pH readings were ~7.2. I do have an opaque, automatic cover which I use most of the time.

John

OK: Added an image. Best I could do--this is looking down the slope into the deep end; best place to see the bubbles with the current lighting.
 

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I've seen the same thing and it's water under the liner. Since you've already had a water table issue, that reinforces the probability that it's water. It'll go away, but as you already know the wrinkles may not.
 
That looks like a problem I had after my pool was built and before I had proper drainage put in. The bubbles will go away and my leave liner wrinkles, however you can get rid of them without draining your pool.

A local pool builder taught me how to get rid of liner wrinkles using the vacuum hose. You turn off the main drain to get max power to the hose, then take the hose under water (wear goggles) and use the suction from the hose to quickly and gently lift and pull the liner while using your free hand to help smooth the wrinkle as you go. It works best if you alternate pulling on either side of the wrinkle. The key is to never let the hose get fully attached to the liner. When you feel the hose start to pull at the liner, slowly pull up and away from the wrinkle while smoothing it with your free hand.

I have removed many wrinkles from my liner and have done a neighbors pool who was ready to pay someone $600 to have someone drain his pool and stretch his liner. I did it in 30 minutes and only charged him a 6 pack of beer.
 
Thanks for the hint about smoothing the wrinkles! We did have a very strange Spring--no rain for 2 moths then quite a bit of rain, but I am still not entirely convinced that it is subsurface water; there was a water issue when the pool was built; the builder didn't put in a pump, but did excavate extensively and lay in a lot of gravel for drainage. The starlike wrinkle I had one year after extensive rains (the sump pump in my house running continuously) I could believe came from that, but my house sump is still pretty dry. I have seen quite a few comments online about this coming from low pH breaking down the liners plasticizer. Do you disagree that this happens? I have tried very hard to maintain proper pH but I know I have had episodes of 6.8 (or possibly lower, as that is the low range for the Taylor test and most strips) but I have done my best to bring it up immediately with borax or sodium carbonate-based products. I did not get a chance to run a full test set yesterday but will do so as soon as I can.

John
 
The fact that you said they fill "squishy" lends to the suspicion that it's water too.
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Yep! "squishy" gives it away for me, too. If it's not water, what else is squishy? air?....that can't happen on the bottom of a pool. Something has to occupy that space and only an equalization of pressure on bioth sides of the liner would let it "float" a wrinkle or bubble.

If acid wrinkled the liner, I would think it to be a series of hard ridges mashed flat by the water pressure from above.
 

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So here's what's happened since my earlier post. The wrinkles have worsened, though unexpectedly (if it was water infiltration) they seem to have gotten worse during a very dry period. They now are are on all the horizontal pool surfaces except the deepest bottom. All run primarilly across the pool. Had the pool installer take a look at it and he immediately thought it was acid conditions, but when I explained that except for a few short dips to 6.8 it has been (except, I suppose, during the winter when I don't test it) at 7.2 or so. Everyone seems to say it needs to be much lower for real damage. A couple of other notes--he says the pool liner seems much more faded than it should be in 4 years. Liner company says it doesn't appear to be a faulty liner (by which they only mean the welds, apparently), so they won't replace it under warrantee, but gave me prorated prices for a replacement . So I have a couple of questions. The current liner is 20 mil. is there any reason to go to 27mil? I realize if water infiltration is the case, the only solution is re-excavation and installation of a sump pump or other drainage (which I don't want to do). I assume once the pool is drained and the liner pulled, the answer should be obvious? I don't want to replace the liner and have it happen again because we couldn't tell.

So what is actually happening in acid damage? Is the vinyl expanding, and then buckling? The installer said that when he's seen water infiltration it tends to pool together into a larger bubble rather than these ridges. I'm somewhat resigned to replacing the liner at the end of the season, but not happy about it.

Lastly, would it pay, if I am replacing the water, to change to a salt based system, so I can avoid the CYA buildup and breakdown into ammonia that I have had the last 3 seasons? Also, could the massive amounts of chlorine needed to break down the CYA have contributed to degradation of the liner? Right now my pool is as far from "trouble free" as I can imagine.
 

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That's an interesting article but that's the first time I've heard of that. I guess it's possible if you got the FC high enough to comprimise the vinyl that it would wrinkle, but there's no other reports of that happening.
 
Well, free Cl is high when I shock, but comes down pretty quickly. I had been keeping my FC a little higher (~5ppm) because of the cya reading (~50). I still wonder though about the effects of the cover, which is closed whenever we are not using the pool) and the high amounts of chlorine I put in 3 years in a row to eliminate the ammonia. While the FC was not high in that case, as it combined almost immediately until the end, that's still a lot of chloride ions that eventually do go somewhere? Anyway, I am still searching for answers. The condensation idea also is somewhat appealing, as it would explain the feeling of water under the ripples; I still say if it was a subsurface water source the ripples would be radiating outward from the source, and the ripples would merge as the water pools together.
 
My liner is heavily wrinkled and faded but it came that way from the previous owners. We assume that at some point either trichlor powder or calhypo sat on the floor of the liner in a few places where it is now faded to nearly pure white.

Prior to our owning the pool however the pool was maintained using Trichlor pucks and calhypo as far as we can tell. We have no idea what the level of sanitation maintained was but I did use a test strip (before I had a kit) and read > 10ppm FC during the time that the old owners had the pool service maintaining the pool for our inspections.

The liner while wrinkled - is working great. There is no water penetration - no soft squishy areas at all. There are depressions where the ground is no longer flat under it - looks like settling more than anything - kind of a moon crater landscape with the light on at night - but more subtle.

In any case I don't think I would blame chlorine yet since my very old and very tired liner has no sign of water penetration despite the major wrinkles. Your liner has few wrinkles but a lot of apparent water behind it - that seems to suggest another problem - perhaps a leak somewhere (pinhole?) that has allowed water to penetrate behind the liner?
 
Vanya, the wrinkles are hard ridges then? The ground seems completely flat under the pool (which makes me wonder about ground water, too--I would think that would deform the floor under the pool). The wrinkles in mine are sometimes hard, sometimes much softer; I've not been able to directly relate that to anything (temp/rain/free Cl/pH) but I really must make an effort. I am planning to replace the liner at some point, but I'll be Darn if I'll let it happen again, so I am really determined to find out what is going on!
 
nagrath said:
Vanya, the wrinkles are hard ridges then? The ground seems completely flat under the pool (which makes me wonder about ground water, too--I would think that would deform the floor under the pool). The wrinkles in mine are sometimes hard, sometimes much softer; I've not been able to directly relate that to anything (temp/rain/free Cl/pH) but I really must make an effort. I am planning to replace the liner at some point, but I'll be **** if I'll let it happen again, so I am really determined to find out what is going on!
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Yes - the wrinkles are hard ridges in my pool. The depressions are softer but bulge out not in and are firm but have a litte give (like a sand bottom might feel). Since i don't know how the hole was prepared for all I know the bottom is sand on this pool.

You mentioned the cover and Chlorine. The article you linked seemed to say that this could be an issue but it sounded like that would cause wall problems close to the cover not problems on the bottom.
 
That's true, Vanya, thanks for pointing that out--I DON'T have any wrinkle problems on the walls of the pool. Would I see that with acid-based wrinkling? That would be a nice way to rule it out. I would think that expansion "buckling" would also show on the walls, though perhaps since there is less pressure, and the "hole" is generally larger than the liner, there's room for the liner to expand without buckling?
 
nagrath said:
That's true, Vanya, thanks for pointing that out--I DON'T have any wrinkle problems on the walls of the pool. Would I see that with acid-based wrinkling? That would be a nice way to rule it out. I would think that expansion "buckling" would also show on the walls, though perhaps since there is less pressure, and the "hole" is generally larger than the liner, there's room for the liner to expand without buckling?
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I don't know. In my case the wrinkles are all on the bottom as I recall. There's an assumption that trichlor or dry acid or something with acidic content sat on the liner for a while in the bleached areas. The assumption is that this happened during cloudy conditions when the bottom was obscured and no one knew it was happening.
 

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