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Thread: Pool subsoil

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    Pool subsoil

    Hello,

    I am an excavator by trade and I am going to be building my first vinyl liner inground pool. The house I live in backs onto a ravine with about three to four feet deep of topsoil in the back yard. I need to raise the height of the pool a couple feet to match the grade at the house. In doing this I may only be digging a couple feet deep into the ground to get to the proposed elevation for the floor of the pool where the pool will sit. This could leave still a couple feet of topsoil under the elevation of the pool. I know when I do excavations for basement foundations we cannot put walls on top of topsoil. I guess what I am asking is should I remove the remaining topsoil from under the pool and fill it back up with some sort of aggregate or sand to the height of the bottom of the pool and compact it before doing the concrete floor for the pool?

    Thanks in advance,
    14X28 I/G steel wall hump back Kidney 3'-5', 30mil vinyl liner,92" spill over spa, 1hp Hayward Super 11-pool circ., 1 hp Hayward super 11- spa booster, Hayward Tristar waterfall pump through Jandy CS100 for three 24" Brilliant Wonders sheer descent waterfalls and two Jandy Laminar deck jets , Hayward Swim Clear Cartridge 425sqft, Hayward H-series 250,000 BTU N/G, Pro-logic PS8, T-Cell, Hayward Aqua Vac Robotic

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    Re: Pool subsoil

    Yea, you will need to strip the loom (thats topsoil for non new englanders) out down to what ever is below. You can bring in some processed gravel mixed with chopped up road asphalt (if you have that kind of material) or you can use 3/4" stone. The stone is nice, but it's expensive and overkill, imo. Processed gravel compacted in 6-8 inch lifts will work fine.

    Thats a ton of loom by the way Any way you could sell that?
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Pool subsoil

    Thanks bk,

    Yes we have that material, we call it recycled concrete. I was going to do the overkill method with 3/4 clear limestone but I like the cost of the recycled much better. I will compact it up to proposed under side of pool.
    Getting rid of topsoil up here is no easy task. Gonna probably cost me rather than make anything on it.
    14X28 I/G steel wall hump back Kidney 3'-5', 30mil vinyl liner,92" spill over spa, 1hp Hayward Super 11-pool circ., 1 hp Hayward super 11- spa booster, Hayward Tristar waterfall pump through Jandy CS100 for three 24" Brilliant Wonders sheer descent waterfalls and two Jandy Laminar deck jets , Hayward Swim Clear Cartridge 425sqft, Hayward H-series 250,000 BTU N/G, Pro-logic PS8, T-Cell, Hayward Aqua Vac Robotic

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    Re: Pool subsoil

    Quote Originally Posted by Butcher
    Thanks bk,

    Yes we have that material, we call it recycled concrete. I was going to do the overkill method with 3/4 clear limestone but I like the cost of the recycled much better. I will compact it up to proposed under side of pool.
    Getting rid of topsoil up here is no easy task. Gonna probably cost me rather than make anything on it.
    Where are you? Here in Mass good screened loom is worth a bit.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Ohm_Boy's Avatar
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    Re: Pool subsoil

    Thought it was loam? Isn't a loom one of those weaving things?
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    Re: Pool subsoil

    Quote Originally Posted by Ohm_Boy
    Thought it was loam? Isn't a loom one of those weaving things?
    HA!

    Well, yea, but in New England, it's pronounced "loom". Just like the town of Peabody is Pee-bu-dee, Quincy is Quinzy, and Worcester is Wu-stah, and the town of Leicester is Lester.
    go figure.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Pool subsoil

    Quote Originally Posted by bk406
    Quote Originally Posted by Butcher
    Thanks bk,

    Yes we have that material, we call it recycled concrete. I was going to do the overkill method with 3/4 clear limestone but I like the cost of the recycled much better. I will compact it up to proposed under side of pool.
    Getting rid of topsoil up here is no easy task. Gonna probably cost me rather than make anything on it.
    Where are you? Here in Mass good screened loom is worth a bit.

    I'm located in Toronto Canada. Too much topsoil in my area.
    What is the best material to use for the bottom of the pool in a cold winter climate? How thick should it be?

    Thanks
    14X28 I/G steel wall hump back Kidney 3'-5', 30mil vinyl liner,92" spill over spa, 1hp Hayward Super 11-pool circ., 1 hp Hayward super 11- spa booster, Hayward Tristar waterfall pump through Jandy CS100 for three 24" Brilliant Wonders sheer descent waterfalls and two Jandy Laminar deck jets , Hayward Swim Clear Cartridge 425sqft, Hayward H-series 250,000 BTU N/G, Pro-logic PS8, T-Cell, Hayward Aqua Vac Robotic

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    Re: Pool subsoil

    Define bottom. Do you mean the soil underneath the bottom, or the substrate right under the liner? If it's the latter, a sand/portland mix with a bit of fly ash is good. Almost the consistency of tile grout. No aggregate is needed. make it ~4 inches thick. Lots of guys use straight vermiculite, but IMO thats a cheap way to go and it wont hold up near like portland/sand mix. They do it because its cheaper and they can drop the liner in faster.

    In terms of substrate under the concrete floor, depnds on whats there. If its virgin soil with a little clay in it, compact the devil out of it with a plate compactor and your good to go. What does your subsoil look like?
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Pool subsoil

    Yes, I was talking about substrate under the liner. I saw a video that showed to put about 2" of poolcrete but 2" didn't seem thick enough to me. I thought I read somewhere that a two stage aggregate concrete base with a sand concrete finish coat could be used.
    I read a couple articles that said the vermiculite was better than sand because it was less abrasive than sand, more porous to allow for a raise in the water table and better insulation from the cold earth. Of course these where from the manufacturers of the vermiculite.

    I believe in my climate pool companies are using a sand concrete mix but not sure if they are just using it in one stage or a two stage. Wasn't sure how thick either.

    The substrate under the concrete floor will have to be compacted recycled concrete to replace the extra depth of the topsoil. Under that below the topsoil layer I believe will be a silty clay.

    I do back onto a ravine with a water shed that runs water when it rains and stands water during rainy months. The water table is pretty high here. I'm sure if I dig down 4' water will start to fill the hole.

    Should I raise the pool up as high as possible to try and stay above the water table or will that not be necessary?
    14X28 I/G steel wall hump back Kidney 3'-5', 30mil vinyl liner,92" spill over spa, 1hp Hayward Super 11-pool circ., 1 hp Hayward super 11- spa booster, Hayward Tristar waterfall pump through Jandy CS100 for three 24" Brilliant Wonders sheer descent waterfalls and two Jandy Laminar deck jets , Hayward Swim Clear Cartridge 425sqft, Hayward H-series 250,000 BTU N/G, Pro-logic PS8, T-Cell, Hayward Aqua Vac Robotic

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    Re: Pool subsoil

    Pool crete is good stuff. Vermiculite is better than sand, but 4" of pool crete (which is bascially portland/sand) is the best, IMO. It looks like tile grout coming out of the truck. Its a fairly dry mix You dont want aggregate in it either, really. Get your bottom compacted, shoot the grade again and if you need to stake the grade out on the slope or in the hopper run the pool crete up to the top of the stake and pull it just like you would a foundation.

    If you have ground water, put a well point in so you can pump it out if you need to. It's done all the time.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Pool subsoil

    Quote Originally Posted by bk406
    If you have ground water, put a well point in so you can pump it out if you need to. It's done all the time.
    During construction only or past that as well? Once the pool is in and full of water is it still affected by the water table?
    14X28 I/G steel wall hump back Kidney 3'-5', 30mil vinyl liner,92" spill over spa, 1hp Hayward Super 11-pool circ., 1 hp Hayward super 11- spa booster, Hayward Tristar waterfall pump through Jandy CS100 for three 24" Brilliant Wonders sheer descent waterfalls and two Jandy Laminar deck jets , Hayward Swim Clear Cartridge 425sqft, Hayward H-series 250,000 BTU N/G, Pro-logic PS8, T-Cell, Hayward Aqua Vac Robotic

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    Re: Pool subsoil

    Yea, you need a dry well. If the ground water gets high enough, it can float the liner if you have to drain a little water for whatever reason. The most likely thing is you will get water behind the liner and it will bulge during heavy rains. A dry well with pump will take care of it. Just put it in when your building the pool.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Pool subsoil

    OK I will make sure to do that, Thanks.
    14X28 I/G steel wall hump back Kidney 3'-5', 30mil vinyl liner,92" spill over spa, 1hp Hayward Super 11-pool circ., 1 hp Hayward super 11- spa booster, Hayward Tristar waterfall pump through Jandy CS100 for three 24" Brilliant Wonders sheer descent waterfalls and two Jandy Laminar deck jets , Hayward Swim Clear Cartridge 425sqft, Hayward H-series 250,000 BTU N/G, Pro-logic PS8, T-Cell, Hayward Aqua Vac Robotic

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    Re: Pool subsoil

    Get your bottom compacted
    Hehe... you said Get your bottom compacted.

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    Re: Pool subsoil

    Quote Originally Posted by Ohm_Boy
    Get your bottom compacted
    Hehe... you said Get your bottom compacted.

    Now now, this is a famly site
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Pool subsoil

    Curious, you mentioned that pool crete (sand/portland) is the best of the 3 bottom options for a liner installed pool. However, I have noticed most builders in the NE quote out their pools with a vermiculite bottom. Can you guys expand a little on what actually makes the pool crete a better option?....is it sturdier?...better feel?

    I think if you could expand a bit on this, it would help some of us who are also following this thread make better decisions
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    Re: Pool subsoil

    Well, like anything else, I guess it's a matter of opinion. Vermiculite is used a lot. It's pretty easy to do and goes down fairly quick. I think in general it does wear faster since it's softer. It's only a few hundred PSI, if that. So..if you have weight on it, over time it will get bumps in it. It actually wont hurt anything, really. Unless it gets too bad, its not that noticable in the day time.
    "Pool crete" is basically a mix of porland, sand, and some times either a bit of vermiculite or fly ash. It's more expensive to do that way, but it wont get lumpy and bumpy like straight vermiculite will. It's ~3000 psi so its really durable. On a liner change, the potential to have to re-do or repair a vermiculite floor is higher than pool crete, for sure.
    I wouldnt get too worked up over the use of vermiculite over pool crete, really. Both are good options. That being said, ifa builder offered pool crete over vermiculite, I'd opt for the pool crete. But, if i liked a particular builder for price, service, etc and he only used vermiculite, I wouldnt turn him down over it.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

  18. Back To Top    #18

    Re: Pool subsoil

    Here is the info I found on Vermiculite pool floors.

    http://www.schundler.com/swim.htm
    14X28 I/G steel wall hump back Kidney 3'-5', 30mil vinyl liner,92" spill over spa, 1hp Hayward Super 11-pool circ., 1 hp Hayward super 11- spa booster, Hayward Tristar waterfall pump through Jandy CS100 for three 24" Brilliant Wonders sheer descent waterfalls and two Jandy Laminar deck jets , Hayward Swim Clear Cartridge 425sqft, Hayward H-series 250,000 BTU N/G, Pro-logic PS8, T-Cell, Hayward Aqua Vac Robotic

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    Re: Pool subsoil

    Quote Originally Posted by Butcher
    Here is the info I found on Vermiculite pool floors.

    http://www.schundler.com/swim.htm
    Of course he's going to tout vermiculite over pool crete, it's what he sells!
    He makes a few good points, but he does have an agenda. Realize that this is not an unbiased article.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

  20. Back To Top    #20

    Re: Pool subsoil

    I realize that, which is why I posted earlier that the info I got was from a manufacturer.

    Just thought someone else might like to read the article.

    With the high water table where I live it might be a good option though. I am going to bring my machine in soon and dig a test hole to check soil conditions. Hope to start excavation of the pool sometime this week. I will post lots of pics as I go along. Headin' out back now to start marking the ground.
    14X28 I/G steel wall hump back Kidney 3'-5', 30mil vinyl liner,92" spill over spa, 1hp Hayward Super 11-pool circ., 1 hp Hayward super 11- spa booster, Hayward Tristar waterfall pump through Jandy CS100 for three 24" Brilliant Wonders sheer descent waterfalls and two Jandy Laminar deck jets , Hayward Swim Clear Cartridge 425sqft, Hayward H-series 250,000 BTU N/G, Pro-logic PS8, T-Cell, Hayward Aqua Vac Robotic

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