Soil erosion under concrete deck

asura1

Well-known member
Jun 18, 2024
49
Barrie, ON
Pool Size
14000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Jandy Truclear / Ei
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Hi all, not sure how long this has been here, is it a cause for concern? Can I just patch this up with some dirt?
 
Do you have a wider angle shot? Can you fill it in to deck height and slope it away from the pool ?
 
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Tried to reach in with my hand, couldn't get to the end of the hole, but I felt some roots growing parallel to the deck with an exposed part (shown in above picture)
 
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I'm not sure what caused it, we only moved in a few weeks ago. Although I'm dealing with a separate leak (Water leaks).

Not sure if this is a coincidence but the hole is just behind the return jet in the deep end.
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I just did an overnight bucket test with pump off and there seemed to be little difference. Should I do a dye test here just to rule it out?
 
What is away from the pool in that area ? (Far shot pics please) Is water running downhill to that spot or is it coming from the pool deck and not running away as it should ?
 
Run your pool pump and keep an eye on that area for a couple of days.

You can dig it out a little with a hand trowel to get a better view.

If there is no visible flowing water, then it’s probably safe to repack it with gravel. It could have been a burrow made by a small animal like a gopher or ground squirrel. We have plenty of ground critters here that dig temporary burrows every night to sleep in. They’re annoying as heck because you wake up and find random holes all over the yard with dirt and rocks spewed everywhere.
 
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What is away from the pool in that area ? (Far shot pics please) Is water running downhill to that spot or is it coming from the pool deck and not running away as it should ?

There is a pond on the left and lots of plants in between.
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To the left of the hole, the soil is visibly depressed, but the surrounding area otherwise is mostly flat.

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I should clarify that this hole is at least one or two months old - I remember seeing that during one of our visits prior to buying the house. There are no other holes like this around the deck.
 
I'm thinking I would stuff a few paper towels in there, pulling them out right away to see if they are wet. Then put dry ones back in and run pump on high with max output there (if possible) for awhile and pull the paper towels after a few hours to see again if water is coming from pool or jet. If not, could be many things, including critters, a void in the ground when they poured it that later settled, rain drainage if that's a low point, etc. I too get critters doing that around my home's foundation and the pool deck. Rotting vegetation from former trees & shrubs can also do it. I had a very slowly developing sink hole (1 foot deep x 6 foot dia impression really) that came from a long-deteriorating tree stump the former owner had removed, then planted sod over it. If not finding any new water coming from the pool, I guess to be through you could always dig down more to investigate before filling with gravel then dirt.
 

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I'm thinking I would stuff a few paper towels in there, pulling them out right away to see if they are wet. Then put dry ones back in and run pump on high with max output there (if possible) for awhile and pull the paper towels after a few hours to see again if water is coming from pool or jet. If not, could be many things, including critters, a void in the ground when they poured it that later settled, rain drainage if that's a low point, etc. I too get critters doing that around my home's foundation and the pool deck. Rotting vegetation from former trees & shrubs can also do it. I had a very slowly developing sink hole (1 foot deep x 6 foot dia impression really) that came from a long-deteriorating tree stump the former owner had removed, then planted sod over it. If not finding any new water coming from the pool, I guess to be through you could always dig down more to investigate before filling with gravel then dirt.

Great idea on the paper trick. It’s also a good way of detecting animals. Around here, if you want to know which ground squirrel (prairie dog) holes are actively used then you just wad up a bunch of shredded paper and shove it into the hole. If it’s active, the vermin will throw the paper out of the hole …

And then that’s when you fill the hole with propane gas a light a a fuse !!! Blow the little $&@ckers up 😡🤬💣💥🌋
 
I'm thinking I would stuff a few paper towels in there, pulling them out right away to see if they are wet. Then put dry ones back in and run pump on high with max output there (if possible) for awhile and pull the paper towels after a few hours to see again if water is coming from pool or jet. If not, could be many things, including critters, a void in the ground when they poured it that later settled, rain drainage if that's a low point, etc. I too get critters doing that around my home's foundation and the pool deck. Rotting vegetation from former trees & shrubs can also do it. I had a very slowly developing sink hole (1 foot deep x 6 foot dia impression really) that came from a long-deteriorating tree stump the former owner had removed, then planted sod over it. If not finding any new water coming from the pool, I guess to be through you could always dig down more to investigate before filling with gravel then dirt.
Sounds like a good plan, let me try this.
 
Soil deep in the hole feels a little damp, but paper towel did not come out wet. I probably didn't reach the end even with a rolled up paper towel
 
In the zoomed out shot it appears that you might have water pooling in a low spot there from rain or irrigation and it could be that the material in that spot just settled down away from the deck. I would consider building up the ground there and all along the deck to ensure that no water can stand against the decking. Make sure you leave drainage for other parts of the yard to get past the pool without encroaching on the ground next to it.
 
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I had to repair some return jets last year due to a cracked jet, but I didn't have an opening like yours. Everyone's suggestions above make good sense and I'd try each one of them to see if you solve the mystery. I don't suppose you have a scope of some sort that you can get down there to see first-hand?
 
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