Fiberglass or Gunite Chicago High Water Table

[claudface1]

Hi,


New to the forum. Have read lots of good info the past few weeks and have finally decided to start a thread.

Looking to get an in ground pool installed. I live in the suburbs of Chicago. (Long Grove, Illinois)

15x39 (possibly 18x40 if gunite).

I have a high water table. Very high water table. I know this from tests and my local septic contractor. It is confirmed.

My options are FG from Latham Corinthian 16 or same design in gunite.

Price for the FG is 100K. Price for the gunite is 160K.

I am not saying money is not a factor, but it is NOT primary factor. I would say longevity with high water table being the main reason for going one way or another.

Am I annoyed the difference is so large? I would say yes because if it was close I would go gunite. Still not for sure, but decision I believe to be way easier!

Just looking for everyones thoughts? Obviously people from this region would be great, but I welcome all comments and appreciate each one!



Excited either way I go!

 

[kimkats]

Hey everybody........................new pool to build!!! Come on over and join in on the fun!!!

High water table-at least you KNOW and can plan on it. No matter what kind of pool you go with you have to plan around the water table. Well points with pumps in them will be your friends.

Do you know why your water table is so high?

With plaster you can put a pool hydrostatic relief valve in so if/when you have to do some draining you can do so safely. You might be able to do that in a FG pool BUT that is another hole in the shell so............

 

[ajw22]

High water table causes more problems with a FG pool.

I would get the gunite pool. You should get a custom set of engineering drawings that include a water management plan. You should sink some well points as water seeping through the gunite can prevent plastering.

 

[claudface1]

Thanks!

When you mention well points you mean like a sump pump? To keep water a certain level below the pool level?

I am not exactly sure the reason but I would say it's my area and I happened to buy a house that's the lowest within the few houses surrounding me. So foolish, but had so much on my head when purchasing I didn't analyze everything like I should.

My sump pumps run very often. Even if it's not raining.

If high water table is enough reason then perhaps my answer is easy. She'll the extra 60k, make it tad longer and wider to make myself feel better I went with gunite, and make sure I get someone who is very well versed in the water management.

I would think my installer will be, but will make sure of it. Actually drawings will be key as mentioned.

 

[kimkats]

well points you mean like a sump pump? To keep water a certain level below the pool level?

Yes that is just what I mean.

My sump pumps run very often. Even if it's not raining.

Ahhhhhh so you are well versed in them. Do you have a basement where the current pumps are?

make sure I get someone who is very well versed in the water management.

This is a real question...............HOW do you make sure someone is well versed in water management? Are there soil engineers?

 

[ajw22]

When you mention well points you mean like a sump pump?

Depending on the topology of your property well points can be designed to drain to daylight if you have a slope that can be used. Or well points can have sump pumps dropped into them to pump water out.

To keep water a certain level below the pool level?

When the pool is full you don't be concerned with the water table. The water pressure inside the pool will be equal to the water pressure on the outside of the pool.

Should you need to drain water from the pool then you may need to lower your water table around the pool through the well points.

 

[claudface1]

So just some additional detail. You mentioned more problems for FG with high water table.

With proper well points and being conscious of pool water relative to water table height what are these problems?

Is it just having the weight of concrete that allows for less movement?

I would think if properly installed it wouldnt matter?

 

[duraleigh]

As a general rule, keeping the water table below the pool water height is good if not even mandatory.

Allowing the water table even or above the pool water relieves all pressure on your liner or begins the process of possibly lifting a gunite or fiberglass pool, It;s a big NO-NO.

 

[claudface1]

I agree. Concept is pretty simple and shouldn't matter what kind of pool installed.

I guess my question is if you follow that safely wouldnt pool type be irrelevant? It was mentioned FG pools have more problems in high water tables. Why? I'm just curious why they would have any more then a different pool if the water around pool and in is managed properly with fill/levels.

Maybe it's the fact having water around a FG versus concrete constantly saturated is just much worse for fiberglass? For longetivity of the shell?

 

[ajw22]

With proper well points and being conscious of pool water relative to water table height what are these problems?

With a high water table you cannot drain of fiberglass pool or even lower the water level without risk of it popping out

In Chicago you need to close and winterize the pool which usually involves lowering the water level some. We have seen fiberglass pools lift when the water was lowered too much for winterization.

Is it just having the weight of concrete that allows for less movement?

I would think if properly installed it wouldnt matter?

A fiberglass pool is merely placed in a hole in the ground and then gravel is backfilled around it. Only its water weight and its concrete collar is holding it in place.

A gunite pool is encapsulated by the supporting dirt with concrete and rebar. A gunite pool has a hydrostatic drain installed to relieve outside water pressure to prevent it from popping out. And many gunite pools have removeable drain plugs on the bottom to relieve outside water pressure if the shell is left empty.