High water table - Fiberglass Pool

[13pools]

Hello,

We are in the process of having a 30x15x6 deep (deep end) fiberglass pool installed by an experienced contractor. Our property is very wet (right against a wetlands). They are setting the pool in the hole tomorrow.

My wife and I are concerned with the ground water under this pool. When excavating a water vein was hit and the hole is continuously being filled with water. Almost as though a garden hose was constantly coming out of the sidewall of the hole. The contractor is using pumps to keep it dry until the pool is installed.

Long term has anyone run into situations where the pump in the sump tube needs to be running 24/7? I’m not sure how high the water will go up the pool but it looks like it will be about 3’ or so. it seems like it would be a lot to have a pump running 24/7 to dewater this pool.. are there hard wired in pumps so I don’t have to keep an extension chord out all the time? At what depth should I be concerned?

I appreciate any feedback on this topic.

Thanks

 

[Wolfepack88]

I have a fiberglass pool that has a dewatering pipe (8" schedule 30 pipe )that goes down slightly below the deep end of the pool which is about 8 1/2 feet and with heavy rain it will fill up sometimes about 3/4 of the way up and then I lower a sump pump down connected to a garden hose and it will take about 8-10 hours to pump out that water. I've had no concern with it floating my pool as my pool has 17,690 gallons in it it and only if I needed to drain it for a repair or resurfacing would I be worried about it since the pool isn't going anywhere with it filled. The issue is if its constantly filling then you might want to go with a sump pump that you use the normal flexbile pvc hose which diameter that will move much more water than a garden hose in the event you need to drain your pool for a repair, otherwise you are not supposed to drain water from a fiberglass pool as it usually voids the warranty.

 

[13pools]

I have a fiberglass pool that has a dewatering pipe (8" schedule 30 pipe )that goes down slightly below the deep end of the pool which is about 8 1/2 feet and with heavy rain it will fill up sometimes about 3/4 of the way up and then I lower a sump pump down connected to a garden hose and it will take about 8-10 hours to pump out that water. I've had no concern with it floating my pool as my pool has 17,690 gallons in it it and only if I needed to drain it for a repair or resurfacing would I be worried about it since the pool isn't going anywhere with it filled. The issue is if its constantly filling then you might want to go with a sump pump that you use the normal flexbile pvc hose which diameter that will move much more water than a garden hose in the event you need to drain your pool for a repair, otherwise you are not supposed to drain water from a fiberglass pool as it usually voids the warranty.
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I have a fiberglass pool that has a dewatering pipe (8" schedule 30 pipe )that goes down slightly below the deep end of the pool which is about 8 1/2 feet and with heavy rain it will fill up sometimes about 3/4 of the way up and then I lower a sump pump down connected to a garden hose and it will take about 8-10 hours to pump out that water. I've had no concern with it floating my pool as my pool has 17,690 gallons in it it and only if I needed to drain it for a repair or resurfacing would I be worried about it since the pool isn't going anywhere with it filled. The issue is if its constantly filling then you might want to go with a sump pump that you use the normal flexbile pvc hose which diameter that will move much more water than a garden hose in the event you need to drain your pool for a repair, otherwise you are not supposed to drain water from a fiberglass pool as it usually voids the warranty.

View attachment 523910

Is there always water in the bottom of the tube? Just curious what to expect.

Thanks

 

[Wolfepack88]

Is there always water in the bottom of the tube? Just curious what to expect.

Thanks

Yes, I always have water at the bottom. I will go out and take a picture of the pipe right now. I'm gonna bet its about half full as I haven't pumped anythign out of it for like over a month. I occasionally just do it just to lower it. So I just took a picture and its below. So about 3ft from the top so I said what the heck let me put sump pump in. Took me five mins to set up, my hose connects to it and I run my hose to a downspout under ground drain about 20 feet away. Easy peasy. Now that will run until tomorrow morning to pump that water all the way down (I put in about 2:05pm). My pool water is about 2 feet above that I would say.

 

[Wolfepack88]

Ok, I dropped the water level all the way down close to the bottom by 9:30pm so about 7 1/2 hours. In the late fall that would take all night as the ground is much more saturated (grass is dormant as well).

Now having said that you said you had water actively filling your excavation hole like a running hose so that is alot of water, so what is your pool builders or better yet an engineer telling you about that. If its constantly filling you would want to be keeping the from exerting too much hydrostatic pressure on the pool. There are far better experts on this site that can give you advice on this. I'm just giving you how I deal with the water that I routinely have around my pool based on my de-watering pipe filling 3/4 of the way up from time to time.

 

[sktn77a]

Your pool should be fine when there's water in it. The problem comes if/when you ever need to empty it - it will almost certainly pop out! I would look into a drainage/pumping solution under the pool. Other pros on this board may be able to elaborate.

 

[13pools]

Ok, I dropped the water level all the way down close to the bottom by 9:30pm so about 7 1/2 hours. In the late fall that would take all night as the ground is much more saturated (grass is dormant as well).

Now having said that you said you had water actively filling your excavation hole like a running hose so that is alot of water, so what is your pool builders or better yet an engineer telling you about that. If its constantly filling you would want to be keeping the from exerting too much hydrostatic pressure on the pool. There are far better experts on this site that can give you advice on this. I'm just giving you how I deal with the water that I routinely have around my pool based on my de-watering pipe filling 3/4 of the way up from time to time.

Thanks for your reply. The builder just told us that we need to keep a pump on the tube at all times. They are not giving much feeback other than that unfortunately. The water stops around coming up at 20” from the bottom. I can get all the water down to the base over night with a 1/4 hp pump. I think I am going to invest in a 1 horse power pump and let it hang about halfway down the tube so that there are no concerns. Then if I ever do need to drain it I should be able to maintain an almost 0” water level with a pump about this size.

 

[13pools]

Your pool should be fine when there's water in it. The problem comes if/when you ever need to empty it - it will almost certainly pop out! I would look into a drainage/pumping solution under the pool. Other pros on this board may be able to elaborate.

Thank your for your reply. Does hanging the pump in the tube at about halfway seem ok?

 

[13pools]

Thanks for your reply. The builder just told us that we need to keep a pump on the tube at all times. They are not giving much feeback other than that unfortunately. The water stops around coming up at 20” from the bottom. I can get all the water down to the base over night with a 1/4 hp pump. I think I am going to invest in a 1 horse power pump and let it hang about halfway down the tube so that there are no concerns. Then if I ever do need to drain it I should be able to maintain an almost 0” water level with a pump about this size.

Also, how much water do you usually have in the bottom? A few inches or is there a decent amount? It should also be noted that we raised the pool 14” out of the ground and are going to regrade off of the pool. We did this with the expectation that we would have a lot of water.

 

[Wolfepack88]

My pump is all the way at the bottom. The schedule 30 pipe had holes drilled around the sides about 2 feet up the pipe and then it was wrapped with landscape fabric to prevent mud and debris form clogging the holes. 3/4" fill was used in that hole at bottom. When my pump is done pumping it shuts off so the water is gone. AFter taking it out and looking today maybe 5 inches or so on bottom). You can hang it as far down or up as you want. If it were me I would go further down than half way but its your call.

 

[13pools]

My pump is all the way at the bottom. The schedule 30 pipe had holes drilled around the sides about 2 feet up the pipe and then it was wrapped with landscape fabric to prevent mud and debris form clogging the holes. 3/4" fill was used in that hole at bottom. When my pump is done pumping it shuts off so the water is gone. AFter taking it out and looking today maybe 5 inches or so on bottom). You can hang it as far down or up as you want. If it were me I would go further down than half way but its your call.

Thank you. We were sold on fiberglass becasue we were told that they could have sustained water under them. Our pool is 14” above where our grade used to exist anticipating these hydrostatic pressures. The pool contractor has now said to keep a pump running 24/7 which seems overkill and expensive, especially if the water lives about 4.5’ below the water in the pool.

 

[Wolfepack88]

Thank you. We were sold on fiberglass becasue we were told that they could have sustained water under them. Our pool is 14” above where our grade used to exist anticipating these hydrostatic pressures. The pool contractor has now said to keep a pump running 24/7 which seems overkill and expensive, especially if the water lives about 4.5’ below the water in the pool.

Then by hanging it at a certain distance down the pipe you will be fine. Like others have said, its if you needed to drain the water from your pool then you need to remove ground water around your pool. So you should be fine and it wont run all the time if you suspend the pump up the tube as you say.

 

[13pools]

I’ve done some investigating and let the water sit for the day and it gets to about 2 feet up the well. Does this seem like a safe height to let the water live at?

 

[Wolfepack88]

I’ve done some investigating and let the water sit for the day and it gets to about 2 feet up the well. Does this seem like a safe height to let the water live at?

Yes not a problem at all. The weight of your pool with full water isn't going anywhere.

 

[13pools]

Yes not a problem at all. The weight of your pool with full water isn't going anywhere.

Ok. I’m more worried about cracking but there’re is a lot of gravel down there so it should be ok. Thank you

 

[Wolfepack88]

Ok. I’m more worried about cracking but there’re is a lot of gravel down there so it should be ok. Thank you

Yes no cracking with that as long as the water in the pool is full the pressure from that is way more than the pressure from that low level of water. Fiberglass is designed to flex as well.