Correct backfill material - runner crush or crushed stone

BlueWRXPride

Active member
Jun 18, 2020
36
Syracuse, NY
I'm working on plans for our in-ground pool install, and I've already determined I am not going to backfill with dirt like is common around here. I want to do structural backfill to prevent settling in the future, and to allow us to have the concrete apron poured without waiting for it to settle. I haven't seen anything definitive on the best material for backfill. The concrete guy I've been talking to suggested something like #2 crushed stone would be good because it is self-compacting, and it's good for drainage, so I wouldn't have water sitting around by the pool walls. That made sense to me. However, my pool installer says that runner crush is better because it has poor drainage, and would act as a barrier preventing ground water from getting around and then underneath the pool, which could potentially cause the liner to float. Of course runner crush is cheaper, but the labor is much more expensive since you have to compact it every foot or so. Which is the right way to go? Or would either be pretty much fine?

Might be worth noting that the ground in my area is like clay, and the spot the pool is going in can be somewhat wet in the spring months.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,378
Tucson, AZ
I’m no expert but crusher run is what is used for concrete base material. It’s basically a continuous mixture of large stone aggregate all the way down to stone dust. True it has to be compacted but, once done, it leaves no voids. This is important if you intend to pour concrete on it. I’m not sure using #2 stone would be appropriate for pouring the apron on to it.

If you’re worried about ground water around the pool, then installing well points and drainage pipes around the pool is the way to go.
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,672
Houston, Texas
If your pool area has an issue with draining heavy rain run-off, it is best to address that problem directly and choose your structural backfill material based on what will provide the best base for a concrete apron. Installing well points,french drains, and/or grading the area around the pool to direct runoff away is the best way of dealing with problem ground water.
 
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Kjp300

Gold Supporter
Jul 18, 2018
135
Canfield ohio
Not sure about the material used but your ground and situation is similar to mine. We have all clay and the pool was installed in a low spot in the yard that collected water before the install.

My PB wouldn’t even install the pool in that spot without drainage. Other bids did not include drainage but he talked me into it and I am glad he did. I am not a construction expert but he installed what I call footer drains (weeping system?) around the pool and was able to drain the water into a storm sewer that was lower than the deep end of the pool. We also backfilled with some kind of stone. Not sure what type but you can see in the picture. I also remember him compacting it. He also raised the pool walls up about 18-24 inches above ground level to make sure all the water drained away from the pool.

I have attached construction pictures. My point is that if the PB mentioned water being a potential problem then make sure he puts some kind of drainage system in and the water drains away from the pool after construction. It is a few extra dollars but well worth it.
 

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jimmythegreek

TFP Expert
Bronze Supporter
In The Industry
Aug 10, 2017
2,937
Morris Cnty NJ
It's very hard to compact road base next to a liner pool. It can be done but it will not stop water all together. The best approach is 3/4 clean gravel up to the sub base. It is self compacting just need to run a plate over it at the end. I use sdr35 perforated pipe on top of the collar pitched to daylight if possible otherwise to a sump standpipe of 10 or 12 inch PVC. I also wrap the overdig in filter fabric and them over the clean stone. Takes a little time but liner never floats amd you can do liner change amy time of year rain or shine
 
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Rich D

Bronze Supporter
Aug 3, 2018
959
MA
my pool installer says that runner crush is better because it has poor drainage, and would act as a barrier preventing ground water from getting around and then underneath the pool,
That is incorrect. Your virgin clay soil is far more impervious to water than any type of crusher run material. The groundwater obviously has no problem running through the clay. No matter what you backfill with the water table will be the same and you will have the same amount of water against your pool. The only way to lower the water table is with proper drainage. The best structural material to use for drainage is 3/4 clean crushed stone.
Using all clean crushed stone as backfill can invite "surface" water down to the sides and bottom of your pool. That is why it is imperative to have a perforated pipe at the lowest point of any stone installed that out falls into a sump or daylight.
Functionally, a pool can never be installed too high. You just need to balance that with the aesthetics. The price of any fill required to raise the pool will be well worth the cost.
 
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