# Exterior sump pit for pool/ground water



## bob22 (May 28, 2008)

I've an inground, vinyl-liner pool near Philadelphia.
Every spring when I open the pool the ground water over the winter puffs up the liner from the sides and bottom. I have to then insert a 1" PVC pipe between the liner and the metal pool side and pump it out. (see pic at left below)
Although the end of the PVC pipe only goes to the bottom of the shallow end (about '4), the water that puffs out the liner at the pool drain (about 9') goes down as I pump. It can take hours to pump it down.

After 6 years of this, I thought if I had a sump pump next to the metal pool liner I could pump the ground water out all winter. My crude drawing is at bottom on right below.

I'd have to cut the sidewalk along the pool to make the pit obviously.
The ground slopes away from the sidewalk so I can pump out to 6" below the sidewalk level and slope downwards.

My questions:
1. Since Philly is frequently below freezing, how might this affect the sump pump process?
2. How deep need I go? I don't want to go much beyond the lower edge of the metal pool liner which I think is about 3'.
3. Do you think this will work?

Thanks,
Bob


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## jogr (Jul 24, 2007)

I thought you were suppose to leave water in the pool year round. Otherwise, eventually your walls will collapse. Lower the level below the intakes, Drain all lines, filters and pumps but leave water in the pool.


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## bob22 (May 28, 2008)

Yes, water stays in it as you describe.
The "billowing" effect must be due to the extensive force of the ground water that accumulates over the winter (very clay soil, I think the water migrates to the hole in the ground created by the pool and then accumulates there.
As I pump the water out behind the steel wall, the billowing goes away (thankfully).
You can see how the liner billows out along the left side of the picture below.


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## Ishmael (Apr 24, 2007)

I'd install it so that the top of the pump is about 4 feet below grade. The sump pit should have a good collar/lid assembly that fits snug, strong and secure. I'd also skip installing a check valve on the pump's discharge line; that way it doesn't stay full of water between cycles which would make it susceptible to freezing.


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## chillz911 (Aug 25, 2010)

There may be a leak in your pool vanilla or the concrete is cracked and pooling water..... I would re line it and repartee the concrete behind the vanilla. ... It shouldn't do that

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## chillz911 (Aug 25, 2010)

I am no expert but have never seen this before

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## bob22 (May 28, 2008)

Chillz911,
Here's another:
http://www.troublefreepool.com/threads/36819-Floating-Liner-Thanks-Irene!


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## landfillwizard (Feb 21, 2014)

If the pool was installed with a porous material (sand) around the outside then the hydrostatic pressure from this material is forcing the the liner in. You will need to drain this layer by installing a perforated sump with a pump. The sump will need to reach the bottom of the pool to insure proper drainage of this layer. If you need maintenance done on your pool, you will also need to drain this layer to keep the hydrostatic pressure form collapsing the wall.


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## bob22 (May 28, 2008)

landfillwizard said:


> If the pool was installed with a porous material (sand) around the outside then the hydrostatic pressure from this material is forcing the the liner in. You will need to drain this layer by installing a perforated sump with a pump. The sump will need to reach the bottom of the pool to insure proper drainage of this layer. If you need maintenance done on your pool, you will also need to drain this layer to keep the hydrostatic pressure form collapsing the wall.


I agree in principal but since the little 1" pipe pump method works and it is sucking from only at most 4' down, I don't see what my idea wouldn't work.

To do as you recommend, would mean pulling the liner from the pool, digging 4' down below drain level, sink a pump in the pit (electrify it somehow without running into code issues), run drain line across bottom, up side, under sidewalk, to exit. That would entail a lot of work and $s IMO (and without guarantee of it working).


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## ct18 (Sep 20, 2012)

I don't think there is anyway of saying one way would work over another. the proper way is excavation and drain tile which you said is most likely out. I would just do what you want and see what happens.

You might want to try and contact a pool company and see if they have any experience with your situation


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