Canyons in bottom of pool liner

[kmerkel]

First off, I don't know exactly how old the pool is. Definitely less than 20 years old since the land was parceled out and the house built in 2000. We just moved in late last year, so this was our first season with it.

Short album here. Hopefully the picture quality is acceptable; I was trying to not drop my phone in the water while avoiding getting eaten alive by mosquitoes. And yes, I know I should vacuum, but the silt actually helped to highlight the features. What would cause this? Mole tunneling, water erosion, something else?

I'd like to fix it since it's a safety hazard, a PITA to keep clean, and there are a couple places where the column footing blocks are poking the liner but fortunately has not punctured it yet. Is that something I could do myself with the help of a few friends, or am I better off calling in a professional? Also, would it be better to do it now or wait til spring?

 

[Texas Splash]

Hummm. Those depressions look like water is seeping under the liner and eroding the soil a bit. One concern might be confirming if the moisture is from the pool itself (leak) or seeping in from around the perimeter. For some with high water tables, water could also be pushing up from directly underneath. So you'd want to know what you're up against so that you could fix the right problem. A liner leak speaks for itself - repair. But if it's from a high water table or surrounding soil seepage, you'd want to look into a type of French drain or sump pump system that could keep moisture from accumulating. Those are my initial thoughts anyways. Maybe others will follow.

 

[PoolguyinCT]

It’s an aboveboard, it’s poor grading.
Incidentally your liner looks like it’s at the end of its service life.

 

[kmerkel]

It’s an aboveboard, it’s poor grading.
Incidentally your liner looks like it’s at the end of its service life.

Kind of what I was hoping on the former, and expecting on the latter.

So what's involved with fixing it? Is it as easy (haha) as pulling the liner, filling and tamping the low spots, and putting in a new liner? Seems like something I could potentially do myself, but it might be better to pay someone that actually knows what they're doing.

 

[PoolguyinCT]

Kind of what I was hoping on the former, and expecting on the latter.

So what's involved with fixing it? Is it as easy (haha) as pulling the liner, filling and tamping the low spots, and putting in a new liner? Seems like something I could potentially do myself, but it might be better to pay someone that actually knows what they're doing.

The fix is miserable & back breaking but simple.
Divert the water run off from hitting the pool.
After that is corrected the easy part is a liner change.

 

[kmerkel]

The fix is miserable & back breaking but simple.
Divert the water run off from hitting the pool.
After that is corrected the easy part is a liner change.

Simple in theory, but possibly complicated in practice. First we need to figure out which way the water is flowing. The pool sits at a bottom corner of the hill where the house sits, and the trenches run for the most part perpendicular to the direction I think the water should flow. The property has very good drainage around the house and yard; I have not yet seen standing water this year, even around the pool.

Seems like this could be more involved than just digging a ditch.

What are the odds that the pool was drained years ago for some reason, maybe for patching, and the base got washed out in that process? The fading in those areas is much worse than the rest of the liner, so I'm wondering if the base has been like that and stable for years, but never properly fixed. From what we've found elsewhere around the house, that seems like a nonzero scenario.

 

[kmerkel]

First off, I acknowledge this is an old thread, but almost 6 years and 2 liners later, to the surprise of no one the problem has not magically gone away, but I do have more information and/or insight on what is happening.

I believe the trench that runs parallel to the pool wall is due to recurring erosion. It seems to be a constant; it has appeared at the same distance from the wall, same length, and same longitudinal position in all 3 liners. We had the walls straightened with the liner replacement last fall, and we found out that the lower horizontal side brace supports are just square steel tubes that go under the liner the same distance as the trench. So it seems that at least along that wall, they are acting as a channel for runoff and erosion under the liner. The pic is from 6 years ago, before the original liner was replaced, but I used it because it clearly highlights the trench details.



The smaller, more isolated ones closer to the edge are most likely due to mole or vole activity, though water erosion is also a possibility.

I don't really want to deal with this right now, but when the liner inevitably fails again, probably in 4-5 years if history is any indication, what kind of erosion-resistant base should we consider? There's sand under the liner, but I have no idea what sub-layers are below that, if any. I would not be at all surprised if it's literally just sand and nothing else. I did some research around on the site and it looks like pea gravel might be a good option? Or would this be better asked in the construction forum? Also wondering if drain tile and/or plugging the supports with expandable foam or something similar so they don't channel water should be part of the solution.

As always, thanks in advance!

 

[Newdude]

First off, I acknowledge this is an old thread, but almost 6 years and 2 liners later, to the surprise of no one the problem has not magically gone away, but I do have more information and/or insight on what is happening.

It's your thread about your journey. Please update it at anytime when relevant.

There's sand under the liner, but I have no idea what sub-layers are below that, if any. I would not be at all surprised if it's literally just sand and nothing else

That's customary for sand floors. They dig the hole, roughly smooth the surfaces then pack and trowel the sand for a smooth finish. Using gravel under the sand won't stop it from washing away or packing further with heel prints or such.

A vermiculite floor is mostly concrete and would reduce seeing small imperfections down the road.

Gorilla pads or foam board would likely hide what's going on down below also.