Hi all, new in this group. Just got my fiberglass pool installed and backfilled. After having to pull it out once to rebalance it due to a sinking corner it looks great and is level. When I walk on the large shallow bench area though, and maybe the last 4 feet on the bottom of the shallow end I can feel the fiberglass vibrate and hear a more hollow sound than in other places. I am hoping there is a way it will settle or whether it should be strong enough to handle the small amount of flex and it does. The pool is a 30'x15' Liesure pool riviera. I love the way it looks just want it installed right to prevent problems in the future. if anyone had to deal with these issues or has some input Id appreciate it. Thanks.
Fiberglass Pool Hollow sound
- Thread starter list2002
- Start date
Welcome to TFP, and congratulations on the new pool!
I'm sorry I can't offer much in the way of help but I wanted to welcome you to the forum. While that doesn't sound ideal, I don't know if it's a reason for alarm. I'd likely feel exactly as you discovering that, but I'm simply not sure. Have you contacted the builder about it? Hopefully someone here can weigh in with something more. Enjoy your time on the forum, and best of luck.
I'm sorry I can't offer much in the way of help but I wanted to welcome you to the forum. While that doesn't sound ideal, I don't know if it's a reason for alarm. I'd likely feel exactly as you discovering that, but I'm simply not sure. Have you contacted the builder about it? Hopefully someone here can weigh in with something more. Enjoy your time on the forum, and best of luck.
- Jun 22, 2014
- 47,759
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Hello and welcome! 
I can relate a bit to what you are describing. As much as the installer tried to pack sand behind the wall, water it down and press it in to create a firm support backing, it seems like some sand still manages to settle even more. If you look at our pool pics from the link in my sig below, you'll see I have two pre-formed benches that run the length of the pool. I can give those a fist-bump (on top or from the side) and it sounds like there is a slight (hollow) gap underneath. Maybe also in a couple spots of the floor I'll feel like there's a little "give" under my foot in a spot or two, but not much. Just no way to get to every nook & cranny. I suspect the nature of the product (fiberglass shell) accentuates it all as well - especially the sounds. At the same time, those shells are extremely strong. I wouldn't worry too much about it at this point. If you believe anything is getting worse over the season, contact your installer and go from there. I hope you have a great swimming season! 
I can relate a bit to what you are describing. As much as the installer tried to pack sand behind the wall, water it down and press it in to create a firm support backing, it seems like some sand still manages to settle even more. If you look at our pool pics from the link in my sig below, you'll see I have two pre-formed benches that run the length of the pool. I can give those a fist-bump (on top or from the side) and it sounds like there is a slight (hollow) gap underneath. Maybe also in a couple spots of the floor I'll feel like there's a little "give" under my foot in a spot or two, but not much. Just no way to get to every nook & cranny. I suspect the nature of the product (fiberglass shell) accentuates it all as well - especially the sounds. At the same time, those shells are extremely strong. I wouldn't worry too much about it at this point. If you believe anything is getting worse over the season, contact your installer and go from there. I hope you have a great swimming season! Are you noticing this while walking around with water in the pool or before the pool has been filled? I am curious to know also what the backfill material is? I just had the 34' model of the same pool installed in August of 2015. After the pool was set on a crushed rock base the builder "jacked" up the bench area from underneath until it was level and supported it in two places with cider blocks. He then proceeded to back fill under the bench with pea gravel. This probably took the longest time out of any step as the hole is not very much larger than the pool that is in it and it is quite a large area to fill on you hands and knees. He was really concentrating on filling that area by pushing material in with rakes and at the end with a 2x4 to make sure it was filled as much as possible. After the water was in it if I go around the bench area and hit it with the palm of my hand I can feel a couple of small voids but they are very small, maybe the size of a softball in circumference. When the pool was empty and I walked around inside of it I could feel a couple of areas that there was a gap between the bottom of the pool and the crushed rock base but I think this was just the natural shape of the pool. When it filled with water these areas settled out to rest on the base material. I hope my experience with the build progress helps you out. I took vacation and watched the whole install from start to finish so if you have any questions let me know. I also installed the electrical myself since that is my field of work and it saved me some money. Before long the construction period will be a memory and you will have a nice pool to enjoy. Currently I have to wait a couple more months for mine to turn back to a liquid from the solid state it is in now.
I have a 5 yr old Viking fibergl pool backfilled with sand, and the first two steps clearly sound like there is nothing underneath. Sounds hollow. It has not caused any issues. These shells are pretty strong. My pool dealer has a 14 by 30 fiberglass shell on display set up on its side ,just sitting in the air for several years . You may want to just go on record about this with your dealer and enjoy the pool. By the way, I just left Maui and am in the plane flying home