Can my broken pool be fixed? (failed weld in the inground metal wall?)

[tturkstr]

TFP has been a boon for my nice clear water for several years, and especially for figuring out what was in my pool house when I moved in and the previous owner had little idea what was going on.
I have a 40x20 kidneyish shaped inground pool with metal sides. I believe about 20-25 years old. Several years ago I noticed the coping? seemed to have a larger gap at one location and it got about 1/2 mm bigger every year? When I ran my finger over the liner below this, it seemed like a crack had formed in the metal side of the pool? I actually had a pool constructor out, who told me it was fine, nothing to worry about, but that fixing it would require replacing the pool, >$50k. Photos of the gap:

New item by Tim Turkstra

photos.app.goo.gl

New item by Tim Turkstra

photos.app.goo.gl

I suspect the problem is that when it freezes each winter, the ice expands the pool (and the crack) slightly, even though I drain about 2.5-3 feet off when winterizing in the fall, but it refills about 1.5-2 feet with snow and rain during the winter.
However, the crack has continued to widen each year and must be stretching the liner. The crack is perfectly vertical and seems like a failed weld? Feeling it through the liner, it feels like it's now about 5 mm (1/4")? Now when I feel around it, I feel some dirt between the liner and the steel. Looking carefully in the pics above, I think you can see a bit of the bulging in of the liner due to the dirt. Incredibly, the liner seems to be holding fine with no leaks. Here is a cross sectional diagram of what I think I feel:

New item by Tim Turkstra

photos.app.goo.gl

I suspect this can't go on forever without failure? Questions:

1. Is there a good/known way to repair this? Ironically, I just poured a new deck over this section last year.
2. How do I disconnect the liner from the pool wall at the top so I can see what's going on and post a picture of this?
3. When I lower the water level this fall, I plan to disconnect the liner at the top and vacuum out the dirt that's between the liner and the pool wall?
4. All I can think of is pulling the liner away from the metal wall and trying to have the metal welded. (I don't weld.)
5. Or I could I drill small holes in each side of the metal and lace it together with UHMwPE fibre (Dyneema, much stronger than steel). I'd use 1.6 mm (1/16") with a break strength > 500 lb, which might stretch ever so slightly but hopefully pull back every spring when the ice melts? However, UHMwPE fibre stretches very little; stretch would be in the lacing geometry. 1/16" holes spaced 3/16" laced would hold > 64,000 lbs/linear foot (32 tons/linear foot), which sounds pretty strong to me, but that's a couple hundred holes to drill! (7/64" is 1600 lb line strength, but then I'd have to drill 1/8" holes... and 1/8" lacing under the liner) What I don't like would be the sharp edges of the holes on the UHMwPE fibre. I could round them on the inside, but not the other side.

Many thanks for any suggestions.

 

[sktn77a]

Welding sounds like a better solution. It you can weld a section a couple of inches on either side of the crack with a continuous weld, it will be waterproof and should strengthen the split so it doesn't progress. Maybe one of the builders on this forum has some experience with your situation?

 

[Yev]

Maybe /u/jimmythegreek can weigh in on this.

 

[jimmythegreek]

Most pools sheet metal is 16 gauge, some higher quality is 14 gauge. Usually after 20yts theres nothing left to bite to other than the supports amd they would be rusty. The ice freezes upwards its not really pushing on the walls. Sounds like your lowering water too much for winter you only want to be below the returns a few inches. Regardless there should be concrete in the collar holding the bottom amd if you have a concrete deck that's holding the top together. The panels are bolted together they are probably rusted thru amd bulging the walls a little if you see dirt. That's why you always hear gravel backfill it wont erode amd stays compacted for support behind walls. Its very hard to fix this from the front. Ideally you would do it from back mostly. With a new deck it's hard to advise considering you have a freeform pool. I would be careful with trying to remove the liner from track. Takes some experience to drape a liner and reset it amd you need warm weather to do it

 

[tturkstr]

Most pools sheet metal is 16 gauge, some higher quality is 14 gauge. Usually after 20yts theres nothing left to bite to other than the supports amd they would be rusty. The ice freezes upwards its not really pushing on the walls. Sounds like your lowering water too much for winter you only want to be below the returns a few inches. Regardless there should be concrete in the collar holding the bottom amd if you have a concrete deck that's holding the top together. The panels are bolted together they are probably rusted thru amd bulging the walls a little if you see dirt. That's why you always hear gravel backfill it wont erode amd stays compacted for support behind walls. Its very hard to fix this from the front. Ideally you would do it from back mostly. With a new deck it's hard to advise considering you have a freeform pool. I would be careful with trying to remove the liner from track. Takes some experience to drape a liner and reset it amd you need warm weather to do it

Thanks very much for weighing in on this. Appreciated. Sounds like I don't have a lot of options.
What about just trying to separate a foot or two of the liner to try and vacuum out the dirt with a crevice tool?

 

[jimmythegreek]

If you think you can swing it go for it. My guess is it will just keep coming back after heavy rains or groundwater up ticks