Will it float? Floating liner answers needed ASAP

[aust1648]

It's going to be a 100 degrees here in NC tomorrow and the pressure along with the temp is mounting.

I am approaching the end of the dig (DIY) but seem to have a difference in opinion with my sub who is going to be putting in the pool bottom (to big of a job for me).

Seems he is of the opinion of two items:

1) After the walls go up I should plumb it in then lay the concrete footer (collar) around the perimiter with the PVC encased in the concrete.

2) My backfill should be the excavated clay (it's NC, it's ALL clay)

I am of the opinion that:

1) I put up the walls, put the footer in and lay/brace the PVC on top of the concrete footer.

2) Backfill with stone and include put an 8" PVC pipe with lots of holes (wellhead) into the decking along with a pump to take out any water that sits behind the walls. I am leaning towards the stone backfill (even though it will cost me) to prevent having to wait 4-6 weeks for the clay to settle to lay the deck as well as to prevent the deck from cracking from additional settling of the backfill

The sub says my method will cause the liner to "float like crazy" but I don't get it. My understanding is that the float is caused by equal water pressure from both sides of the walls, but a stone backfill that has a way for the water to get out should not cause this. Also, why encase the PVC plumbing in the footer? Seems to me that has the potential to crack the PVC piping more then laying it on top of the footer and backfill (carefully) with stone

So, what is everyones take on this?

Thanks!

 

[duraleigh]

aust1648 and I spoke on the phone about this (we live close) and he and I are of the same opinion but we need some more input.

Backfilling here in NC with heavy clay is really troublesome.......it can take a year to settle correctly. I think he should use stone so he can pour concrete immediately. It'll cost a few hundred bucks but it solves a lot of problems.

I just can't understand the reasoning behind encasing pvc in concrete. any movement of the concrete almost guantees a crack in the pvc. It makes sense to me to lay the plumbing on the footer.

I know several of you have done this type of install so let us know your opinion.

 

[crewchief47]

The builder putting the inground in next door to us has encased the flex pvc in the concrete footer as well as back filled with the clay from the hole (and let me tell you about the concrete style clay we have around here....). Some stone on top with a tamper and they'll be pouring the deck in the AM. I have to assume he's been doing it this way for years (22 according to the site). I'm not sure I'd be worried about flex PVC encased in concrete, it should be well below the frost line, of course my opinion doesn't mean squat since I don't build pools or have an inground :blah: . http://www.lakesidepoolsandconcrete.com/ if you wan to check out his stuff. (he works both sides of the border)

 

[bk406]

1) No to the encasing the PVC in concrete. Pour the collar first, then plumb it.

2) As far as backfill, a big NOOO to clay. IMO, 3/4 stone should be used up to a point. Here is where my opinion changes a bit. I would not use stone all the way to the top; thats over kill. I would top it all off with processed gravel, at least 24 inches. It will compact better for the decking material, either concrete or pavers. I'm also of the opinion that no matter what the backfill material is, the decking should not go in for a few months, preferably the following spring.

One exception would be if you used flowable fill. It's a material that's sold by concrete companies. It flows like thick liquid (looks like drilling mud if you are familar with drilling wells). It reaches maximum compaction in a day, and can be shoveled just like dirt once it sets up. Check out the local concrete companies, somebody sholud have it. I dont think it would be anymore expensive than all that stone.

 

[duraleigh]

bk,

I am not familiar with flowable fill. Does it have moisture in it? Delivered in a typical concrete Truck?

 

[jasonknox]

I do not recommend incasing any PVC in concrete. If there is a break in the PVC the concrete could make the fix harder. As for the back fill. I had considered some other backfill material such as sand so that compaction could have been achevieved easier and more through. I choose to backfill with the excavated clay so that the undisturbed soil was the same as the soil I backfilled with. My reasoning for this is that water is going to travel the path of least resistance and any backfill other than the original clay had less resistance and therefore the water would migrate toward the sides of the pool and down the liner. I am not sure that the liner would float but I wanted to shed off as much water as possible. This being said I built my own pool with concrete block wall poured solid with concrete so I was able to get a vibratory compactor close to my walls and compact very well. Clay needs to be compacted in 3" increments. Not quite sure how to acheive good compaction on kit pools. If possible, try and get some sort of separate warranty with regard to the backfill. Also keep in mind that your decking, if installed, will direct water away from the pool. On a side note if the person pouring your concrete deck states that his concrete will not crack go ahead and kick him off the job. Expansion joints will minimize cracking but will not alleviate it.

 

[duraleigh]

Informative post, Jason. My pool was concrete block walls as well. Your points about drainage are well taken. I chose 3/4" stone for backfill reluctantly (cost) but I was able to lay a French drain at the bottom of my pool walls on top of the footer so rainwater travels pretty freely around the pool and is piped out of the drain well below the pool level (I'm on a pretty good slope).

My thinking on using the 3/4 rock is....

1) Really, it is very difficult to compact it further once it's put in the hole. I put a plat vibrator on it and couldn't get a 1/2 inch of settlement however the rock had been in the hole a couple of weeks. Our clay here, even compacted in 3" lifts, is VERY difficult to get stable.

2) Yes, the rock does allow water the easiest path but that actually is a benefit for mein that the water is directed to the French drain pipe at the bottom. In the worst of storms, I have observed water ciming from the French drain in excess of 10-15gpm.

Since aust1648 does not have a slope for drainage, I have talked with him about installing a wellpoint (8" pipe with holes) down alongside the vertical walls of the pool. Any water that accumulates next to the pool should easily flow into the wellpoint and can be pumped out with a submersible pump. What do you ya'll think?

 

[Bama Rambler]

The only time you should encase PVC in concrete is if it's conduit and carrying above 600 volts or running across a roadway. I think we're all in agreement about not encasing the piping.

I agree with using the stone and building a french drain. The drain needs to be at or below the bottom of the pool to work correctly.
The sump should be a little below the drain pipiing.
There should be two float switches in the sump. One to energize the pump and one to flash a light in case the pump doesn't come on for some reason.
At the furtherest point away from the sump there should be an injection or cleanout point so the drain pipes can be cleaned and inspected.

 

[bk406]

bk,

I am not familiar with flowable fill. Does it have moisture in it? Delivered in a typical concrete Truck?

Dave,
read this. It will give you an idea of what it is. It's delivered in a regular concrete truck, and sets up in a few hours. It's "excavatable" as well. Depending on the composition, you can dig it with a shovel, or if its firmer, a backhoe. Depends on the application.

http://www.flowablefill.org/Index.htm

 

[waste]

Welcome to TFP!!

So far in agreement with keeping Sch 40 PVC out of the crete, putting flex in the crete, gravel as opposed to clay as backfill, curtain drain with well point and getting out of work at 2:30 when it's ~100* with ~ 100% humidity

About all I have to add is to surround the pipes in 6" sand before adding the gravel, you don't want them just laying on the footing nor let the gravel 'bounce around' off of them. Also, protect the drain pipe with weed block fabric to prevent roots from clogging the pipe.

If I think of anything else, I'll let y'all know.

 

[aust1648]

Thanks everyone...I am 100% sold on the getting the footer in now without the PVC encased...Good, it will save me from having to plumb just yet. Here are my next steps:

1) Wall assembly finished this morning (early morning to beat the heat).
2) Tonight, square and level walls (thanks to Dave for letting me borrow the transit)
3) Put the footer in Friday
4) rough in plumbing at pool walls
5) Vermiculite pool bottom on Monday (hiring that part out)
6) Drop vinyl ASAP (trying to beat the rains)
7) Install drain around perimeter
8) Plumb
9) Drop sand in around PVC
10) Backfill (the flowable stuff looks interesting...Will check that out further)
11) I can't think farther then 10 tasks...

Bob