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Leaking Gunite Pool...possible Causes....ways To Patch?


etbrown4

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I have a large 10 yr old gunite pool which has been leaking for some time, however with the moderate earthquake in Va last year, it has been leaking more. About 2-3" overnight. Leaking stops about 6" below the normal water level.

All of the skimmer and return lines have been pressure tested. No leaks found at main drain, pool light, or in or around skimmer boxes. There is no equalizing valve.

At this point we're down to 6-7 vertical hairline cracks in the sidewalls at various places. They are so fine you can't get a fingernail to catch. The cracks start about 4" from the normal water height and are 12-20" in length.

If we have covered all usual potential leaks, we're just left to wonder about those cracks, and can imagine that at least in theory, they could be leaking that much.

If others think that amount of leaking from these cracks is possible, what's the best repair process to follow which will not be unsightly?

Thanks for any tips!

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If the cracks fail the dye test, they are likely the cause. Remember, they are leaking all the time. Also remember that the water is going somewhere behind the shell and likely washing any soil away. The cracks may have developed from the soil moving away at some point. Whether it was the earthquake or not, I can't say.

Are they cracks close together or are they spread apart, distance wise from each other?

How long are the cracks?

How many are there?

What was the finish used on the pool?

Do you have pictures from the build?

Has the builder said anything?

I saw the post on Gardenweb too but chose to answer here for a couple of reasons, mostly personal in nature. Keeping them separate though, helps you too so you can get independent opinions.

Scott

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The cracks are spread around the pool maybe 10' apart. All the cracks are vertical, and on the sides of the pool.

The pool is drained down about 30" and I can't see below that because it's green right now.

All of the observed 6-7 cracks start about 4-6" below the normal water surface and extend down about 12-20" and then they stop.

Not sure of the interior surface, but from what I can tell it's some kind of plaster. Up close it looks like tiny gray stone granules. Before I learned of the typical plaster lining, I first thought the tiny gray granules were the gunite itself

Nominally it's considered a black pool, but truly it's dark gray. Possibly it's not plaster? Not sure of the other choices.

Would offer pics, except the pool is 200 miles away on the outer banks of NC. maybe later....

I have no access to the pool builder or the original plans due to it's age of about 10 years.

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10 years for a builder may or may not make a difference.

The finish is likely toasted with that many cracks but since we don't know what ones are leaking, it possible that only one is leaking and the finish may be patchable.

If the cracks are that far apart, it makes things not good for you. It tells me that the cracks go around at least one end and that the settlement may require a professional engineer for both soils and the cement that makes up the shell. 30 inches is a lot of water. If you lose 3" a day, it will be very difficult and expensive to replace the water and chems daily. Also, at 30" down, if the water table decides to rise suddenly, the entire pool may pop up and that would be truly expensive. A diver can't determine with a dye test there the cracks are letting water out. Vertical cracks usually indicate a loss of side support. With a quake, I would have expected som bottom cracks too but you haven't mentioned them. That was why I was hoping the original PB was available for added information.

Scott

You'll notice I am leaving Gardenweb answers separate and that some will agree and some will disagree. Expect that. Also go by experience, We have no pics. People with deffinitive answers but no pics or actual visuals should be, IMHO, disregarded.

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The pool only leaks down 4-6" below its normal level on its own. The 30" reduced water level is just due to winterizing.

I wish I had pics but I'm 200 miles away. If I had pics, you would see the faintest cracks imaginable. As I mentioned, you can't catch a fingernail on them. They are true hairline cracks as thin as a human hair! As mentioned, they are more or less vertical and stop about 30" deep at the deepest.. They are kind of spaced every 10-20' around the perimeter walls, with about 2 per wall - but not close to each other.

Don't know yet what's on the bottom because it's green. At the end of last season we did not see anything.

Right now my plan is to patch or fill them, then add water in a few weeks, and then dye test them to see what we have! :)

My question for now, is just - what's the best way to fill or repair these ultra fine cracks. ? Vulkem 116, Silicone, other?

Temporarily, would it be best to try to fill or skim over them, or should I try to cut a notch with a diamond blade to give me more to fill? (keeping in mind we aren't sure yet if they are leakers.) :rolleyes:

Many thanks for any tips!

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A temp fix may not fix anything and can cause serious additional damages. This is especially true it the cracks have caused the rebar to separate and the lack of support makes the cracks widen. I am serious when I said you need an engineer's report on the soils and concrete. One small crack is one thing, 5 or 6 is another. The difference will be a saved pool versus a lost pool. That can add up to $40,000 or more to replace. Know the cause and fix that first. You may otherwise wind up putting a band aid on a 10" gash, pretty useless and wasted money too. There is no cheap fix for this no matter how much you want it.

Scott

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Sure, it could be that there is a problem with the pool shell, and it could be that soil behind the pool walls or beneath the pool has weakened or eroded.

Likewise it is possible that none of the 6-7 tiny vertical cracks is even a leak! Many times hairline cracks in the plaster occur, due to either a bad plaster mix, insufficient adhesion to the shell due to improper prep, and an improper curing process of the plaster once it's installed, among other possibilities. Even plaster age can be a factor as some report plaster replacement between 10 and 20 years, though often longer.

So before we sound the alarm bells, we need to see if the cracks are a source of a leak.

The only question we're focused on right now is whether to temporarily repair the plaster with caulk etc. while the water level is down and the plaster is dry, or to refill the pool first and then do the dye tests.

All seasoned pool pros know that when you are doing leak detection, it's wise to never eliminate ANY possibility. At this point with this pool, there are still many unknowns: The leak(s) still could be in the tile at the water line, at the joint between the skimmer and the pool wall, or even anywhere below the water line as that's still obscured by the presently green water!

If, and it's a big 'IF', the plaster cracks were caused by the minor earthquake centered 200 miles away, last August, we still need to see if the shell was affected. Clearly the plaster cracks may be in front of shell cracks, but it's possible they aren't.

I'd say let's 'look before we leap' and make sure we've covered every possibility.

In the mean time if other posters have ideas on what to use to temporarily patch the plaster that would be a great help.

It would also be helpful to hear the pros and cons of trying the repairs now before refiling vs, doing them later if the dye tests don't show leaks at the plaster cracks.

PS. If any visitors to this forum want to see a Dramatic Pool Structural failure, here is a link to pics which will take your breath away! It is a catastrophic loss and a tragedy for the homeowner/victims. http://ths.gardenweb...6492617054.html

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Maggie is having a grand time with this. Her builder seems to be doing the right thing but we haven't heard much from her since. But note that her's runs across the bottom too, in addition to the verticals at the structure and where the ground drops off. Your's was on;y reported on the sides but each was several feet away from the next.

As for your situation, until we have pics and a proper eval, like I said earlier, nobody can say definitively. Anyone that does is telling you a story.

Scott

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Let me try and help diffuse the tension. "We" the pool professionals on this forum offer our advice for free. We are not compensated nor rewarded and seldom thanked for our free experienced advice. "We" also take very seriously our expertise in our field and have often times learned lessons the hard way. "We" seldom will encourage a bandaid for a repair because we believe in doing what we do the right way.

It is my opinion that Scott is encouraging you to find the problem not the solution. I will too! If you want a bandaid for your cracks in your plaster pool (because it is a plaster pool despite it's "finish" diamond brite, pebble tech, etc.) then please google band aid for my plaster pool. If you want a professionals free opinion then you have found that! Scott has not suggested you sound the alarms and replaster the pool. He (and I support) has suggested you have a few test run.

With that said? Don't fix what isn't broken. Determine if the cracks are leaking before looking for a solution. If you have to fill the pool to run a dye test, then fill the pool and run the dye test.

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Thanks for the latest post!

I am sure that all posters are here to try to help others. Obviously no one is receiving compensation, and I agree that it is extremely kind for posters to help others!!!! Any tips or suggestions are very much appreciated!!!

The latest, and much appreciated suggestion is to take the next logical step. I had proposed exactly that and really had originally just asked for suggestions if folks on this forum thought should try to caulk or cut out and fill those tiny cracks before refilling the pool and doing the dye tests !

Here's the area where I get a little off track:

Since this pool stops leaking at around 6" below it's normal level, don't we want to focus on 6" and above?

I'm sure that Scott is a solid contributor here, and has helped lots of folks! Nonetheless, I'm having a little trouble understanding the statement, "A diver can't determine with a dye test there the cracks are letting water out." Doesn't that depend on the elevation of the crack? Possibly he is referring to any portion of a crack which may lie below the water table. At that depth, I can see the reasoning, however these cracks are above the water table and current pool water level. Given that - a dye test should confirm a leak once refilled. Right? The pool is drained down for the winter to 30" from the top and that exposes all of all known cracks. If they were above the water table, and penetrated through the shell, I would have incoming water. Right? At the moment they are dry.

Here's the other place I get off track: Scott mentioned, " It tells me that the cracks go around at least one end and that the settlement may require a professional engineer for both soils and the cement that makes up the shell. 30 inches is a lot of water."

Sure enough, there are 1-2 cracks on each end and each side of this pool. They're pretty much evenly spaced around. They are not on just one end etc. If there has been settlement, it's not apparent yet, as there are no other cracks, nor sagging concrete. ( I agree that could come)

I think there may have been a small misunderstanding. Since this pool stops leaking at about 6" below the normal level, that's pretty close to the top of any of the vertical cracks - so the cracks may be involved, and also may not be. I mentioned that I have drained the pool down to 30", in the OP.

Given that, I will continue to focus 6" and above - especially at the tile line with 116 linear feet of exposure. Once I get through all that, it may be time for a geotech or structural guy - but only if i can prove leaks in the cracks.

For what it's worth, I don't mid finding that the leak is at the tile line or that there is an entire structural failure. Whatever it is, I will have to deal with it. I just want to be sure I don't get ahead of myself or overlook anything. I feel sure that everyone can agree with that approach, so maybe we are all on the same page after all ! :)

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At no time did you mention that the leak stops 6" below the waterline.

When you mentioned the water is 30" down, I was under the impression that that is where it stopped too, not just a lowered level for Winter, which is way too low to begin with also.

You mentioned 6 cracks, 10 feet apart. Thats about 50' to 60' of linear distance. That is a long way around. That is why I fl that at least 2 sides were cracked. Now you say 4 cracks. Still some distance but not necessarily 2 sided.

There may be staples needed or just filling with epoxy. Caulk and silicone will be either self leveling or just too soft for this. There may also be some back fill required, mud jacking to re-level, or even a larger area exposed to reveal any broken rebar that needs to be repaired and then filled.

As I said, without a professsional on site and pics, nobody can offer the right repair, unseen.

Scott

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Hi Scott,

Thanks for the additional tips. I think I just didn't communicate well. So keeping the record straight....... I'm filling in some of the past info........

From the original post, "I have a large 10 yr old gunite pool which has been leaking for some time, however with the moderate earthquake in Va last year, it has been leaking more. About 2-3" overnight. Leaking stops about 6" below the normal water level."

Then from the second post, "All of the observed 6-7 cracks start about 4-6" below the normal water surface" ........and ....."The cracks are spread around the pool maybe 10' apart." (maybe really closer to 15')

What we've needed here is good communication, and now that we're on the same page, we can make progress!

As for the next step, it's looking like filling water and dye testing.

There seems to be little doubt that we'll save for later any back fill which may be required, any mud jacking to re-level, or exposing even a larger area to reveal any broken rebar, since right now we don't know if any of that exists.

Thanks for hanging in there!

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  • 2 weeks later...

A Likely Solution? :rolleyes:

I believe I have found and stopped the leak. At least for now, and seemingly for the most part. I'm posting this in thanks for those who contributed above, and hopefully to help others who may encounter a problem like mine in the future!

I was loosing 4" overnight and now, it's maybe 1/4" or less overnight. (Temps here are 40-50 so evap should be at a minimum). I realize I still may have some small leaks.

I spoke at length with a guy who plasters new pools professionally, asking about those hairline cracks. He said that since they were above the winterized water level, he suspected that they were due to drying out of the plaster with the water level lowered. He finds that the hairline cracks like mine usually disappear once the water level is raised, due to adding moisture back to the plaster. He said that in 20 years of plastering pools, he had only found one pool materially leaking through this kind of hairline crack.

So just to be cautious, I did apply a skim coat of silicone to them before refilling, though they were not my main suspects!

I got on a mechanic's creeper and spent several hours examining the tile line around this 40' pool. I found about 8-10 openings in the grout between those tiles at various places from 1/4" up to 2".I cut out the bad grout and replaced it with silicone for a temporary repair. I know that matching grout might have been better - I just didn't have any available on short notice.

I also spent a fair amount of time in and around the pool side openings to the skimmers. There was some obvious missing grout there, and I did carefully seal the vertical and horizontal joints between the skimmer box and the plaster. (On my pool, that vertical joint was up inside the skimmer, maybe 4" from the face of the pool wall) I let that cure about 8 hours and filled the pool.

So far it's 95% better than before! Now that I can finally keep the water level up to the skimmers, I can finally run the pump . Once we get a clear pool, I will dye test everything around the tile line, the skimmer box, and those pesky hairline cracks, just to make sure.

Interestingly, in posting this on this and a few other forums, I don't recall anyone suggesting a look at the tile line. Thankfully, numerous folks did suggest having a look at the interface between the skimmers and the structure.

It's a great relief so far, though I know I will have to keep an eye on things, and maybe later cut out the silicone and replace it with grout! :)

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  • 2 weeks later...

I have a slow leak I've never been able to definitely pinpoint and it may be what you are describing. Am I understanding correctly that you found cracks or holes in the grout around the tile in the pool at the top of the waterline, and that caused water to leak out? And just repairing the grout (or filling it with silicone for temporary fix) stopped the leak? I have examined my skimmer on several occasions and never saw a crack...but still I tried patching around the edges thinking it was a crack I couldn't see. If cracks in grout around tile can cause water to leak out, I will definitely look closely at all my tile grout too. I've not heard that before.

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  • 5 years later...

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