Backfill question!

[raquelgarcia]

Good morning. We purchased a DIY fiberglass in Northern California. Our soil here is a bit clay-e. We were advised to use peagravel and sand for the base and sand for the backfill. Our pool will be installed later today close to the evening and we have the base prepared A layer of pea gravel and 3" of concrete sand. We did not get enough concrete sand so my job this morning to is to get some from a local yard however I was up late last night reading all these forums that say NO-No to sand because it settles.

I am wondering if these forums are location specific in areas with high water tables or if it even matters?? Everywehere I read is a big NO to sand (including forums on here ) and they advise to use some sort of gravel (3/4" crushed blue stone) Our pool is a Viking Pool - the Monaco which is the largst 40" one they have. I am looking for guidance on the remaining backfill that i need to purchase this afternoon. The base foundation is already laid so not much that we can do without canceling today's install. What is your guidance on material for the backfill? Should I order the 3/4" blue stone? Any help, tips guidance is much appreciated as we are doing this on our own with the guidanece of someone that has worked in the industry for 20 years (however he is a big sand fan!) Thanks in advance for your help.

 

[cowboycasey]

Welcome to TFP

I almost messed this up but I read the document below

sand is cheap and easy.. it works for a while until the water washes the sand away and it is no longer the installers problem...

3/4 clean gravel is not going anywhere ever unless you move it and it compacts out of the bucket to 95% compacted...

Gravel Around Pools - Further Reading

www.troublefreepool.com

Large gravel is not to be used against a fiberglass shell. Gravel is a loose term here, There are MANY grades of stone. Pea or similar is the proper base and backfill material even down to turkey grit gravel is fine for the base as this area can and will be mechanically compacted.

The sides need angular like 1/4" up to 3/8 max and some even use course sand and grit mixes. All fine to use. When we talk about clean stone or #57 gravel etc we imply we are backfilling against a steel wall or concrete pool not fiberglass...

Hopefully this should make you feel better

 

[Aquaman7]

I would call the place that sold you the pool. They should know the right material to use.

 

[raquelgarcia]

Thank you. So it would be safe to use a combination of 3/4" crushed stone and concrete sand? Sorry for my questions, all this pool terminology and various types of stone terms are foreign to me! I have attached a photo of our hole!

 

[raquelgarcia]

I would call the place that sold you the pool. They should know the right material to use.

Thank you. The pool manufacturer (Viking Pool) advocates for sand. Due to the all of the forums including one of River City Pools has, and the comments regarding settling if sand is used, has scared us into second guessing what the manufacturer has recomennded. All the forums i have seen talk badly about sand primarily because they claim it "settles." I'm not sure if this is only a problem where the water tables are high but I felt like i wanted to research a bit more before going out and buying 20 tons of sand!

 

[cowboycasey]

Lets see if we can get some more help..

@jimmythegreek

What would you use?

 

[jimmythegreek]

3/8 stone or 1/4. I wouldnt use only sand and dont use 3/4 mixing in sand. Angular stone interlocks with little compaction needed, anytime you introduce fines into a mix you need very thorough mechanical compaction. The key is to get the dig detail and set screeds with a transit or laser amd screed the base. Then set pool amd fine tune as needed, they aren't built perfect so always adjust then walk the pool for hollow spots. Backfill with same stone amd keep water amd backfill equal as you go

 

[raquelgarcia]

3/8 stone or 1/4. I wouldnt use only sand and dont use 3/4 mixing in sand. Angular stone interlocks with little compaction needed, anytime you introduce fines into a mix you need very thorough mechanical compaction. The key is to get the dig detail and set screeds with a transit or laser amd screed the base. Then set pool amd fine tune as needed, they aren't built perfect so always adjust then walk the pool for hollow spots. Backfill with same stone amd keep water amd backfill equal as you go

Thank you. Okay, we ended up setting the pool with the crane company we hired however, the man that was helping us install could not get it leveled and after 4 hours it was 2" off on the right corner. I will provide more details (please bare with me since we are feeling rather frustrated and helpless through this process!)
The install man we hired (he claims to have been in pool industry for 20 + yrs) asked us to purchase a transit to ensure the hole was dug out properly and to the exact measurements.
My husband's buddy helped dig the hole following the pool's excavation specifications. He used a laser to verify the measurements.
The day of the install, the man we hired set out the transit we purchased and right before the crane was going to bring the pool down, he said that we were off by 10" on the deep end. So we hurried and dropped a bucket full of sand (which was a lot of work to do in such little time) We spread it, left it looking pretty good, then he looked at the transit again and gave the thumbs up to bring down the pool.
The pool was brought down, he went down to the hole to look under the pool then he brought out the measuring stick and used the transit to measure every corner of the pool. To the naked eye, it looked perfect! My husband even pulled a level and placed it on all sides of pool and it appeared level. BUT, the man said the transit was showing that it was NOT leveled. So he had the crane guy pull the pool back up and he had us remove the 10" of sand that we had just poured in (at this point my husband and i were looking at each other and wondering if he knew what this man was doing!!) After 30 min of removing the 10" of sand , he directed the crane to bring pool down. To make this long story short, 4 hrs of adding and removing sand and bring the pool up and down, he finally said, "We can't get it leveled. The right corner is off by 2" but all other sides look good. Let's let the crane guy leave and I will come back on the weekend and we can start filling it. We will reinforce the side that is level with plenty of backfill so that it doesn't go down anymore as we are pouring water and letting the side that is not level go down the 2"" This is truly what he told us!! We are down this project far enough to where we cannot turn back but we have enough common sense to almost be certain that this plan does not make sense! We think it should be as leveled as possible before we start filling it.

Can anyone provide any guidance on this!! We can't afford to bring the crane company out again but we do have machinery that we can borrow to have it lifted and do what we need to, to make it level. A side note, he never walked the pool as we were setting it. And after everyone left, i went inside the pool and noticed there were areas that would sink in.... I am assuming we need to fill these areas with sand??

I hate to push all these details on this forum, and I thank anyone with experience for their time in reading this and giving us some tips to help us get this done right. I am not feeling confident in this pool guy we hired and to be honest, there aren't many people in the industry in my area , otherwise I would pick up the phone and pay for a crew to come out and help!!

 

[jimmythegreek]

I dont know where to begin. First thing is to run some jet line (used in drop ceilings it's like dental floss home depot has it) amd string the pool shell from corner to corner. You want to be sure there isnt a bow in the shell. If its straight have ur husbands buddy come back w the laser and have him check it. A transit is only good if its leveled properly, amd I doubt this guy knows how to use it properly. A self leveling rotary laser is way better

 

[raquelgarcia]

I dont know where to begin. First thing is to run some jet line (used in drop ceilings it's like dental floss home depot has it) amd string the pool shell from corner to corner. You want to be sure there isnt a bow in the shell. If its straight have ur husbands buddy come back w the laser and have him check it. A transit is only good if its leveled properly, amd I doubt this guy knows how to use it properly. A self leveling rotary laser is way better

Thank you! We were able to do this and the shell is not crooked, they were able to get it leveled thank goodness! Today we have concrete sand coming as well as crushed stone (a combination because the hole was dug too big. We decided to use concrete sand around the pool then fill the balance of gaps with the crushed stone to avoid major settling. The pool is 1/4 filled with water and we should be doing the backfilling later today or tomorrow. IS there a time limit on how long the pool can be left unfilled to the top?

Also, are there any videos that you can share that provides information on the plumbing process. My husband will be working on this while the backfill is getting done. Thank you for getting back to me!

 

[jimmythegreek]

Be careful adjusting the base for pool, it has to be solid with no voids. Many a fiberglass pool have been spider cracked by poor base install

Dont mix sand amd 3/4 stone. Water will carry the sand into the voids of the larger stone amd it will settle with time. Only 3/8 or 1/4" stone for fiberglass pools. If the hole is too big you will have to just eat the cost of stone. Theres no other way really. What's the plumbing plan? Did the shell come pre tapped with skimmer installed or?

 

[raquelgarcia]

Here is the photo of the skimmer and also shows the type of rock we purchased. We did use some concrete sand and watered every 5-8 inches. We didn't purchase enough so today we will be bringing more. i will follow your advice and bring in more stone.

In regards to the entrance of the pool, there are several steps. We were told to add pressure treated wood underneath the steps so that they don't sag over time. Has anyone heard of this ? What is the best practice as far as backfilling under the steps to prevent sagging in the future?

 

[NJpoolNoob]

Thank you! We were able to do this and the shell is not crooked, they were able to get it leveled thank goodness! Today we have concrete sand coming as well as crushed stone (a combination because the hole was dug too big. We decided to use concrete sand around the pool then fill the balance of gaps with the crushed stone to avoid major settling. The pool is 1/4 filled with water and we should be doing the backfilling later today or tomorrow. IS there a time limit on how long the pool can be left unfilled to the top?

Also, are there any videos that you can share that provides information on the plumbing process. My husband will be working on this while the backfill is getting done. Thank you for getting back to me!

Here is the photo of the skimmer and also shows the type of rock we purchased. We did use some concrete sand and watered every 5-8 inches. We didn't purchase enough so today we will be bringing more. i will follow your advice and bring in more stone.

In regards to the entrance of the pool, there are several steps. We were told to add pressure treated wood underneath the steps so that they don't sag over time. Has anyone heard of this ? What is the best practice as far as backfilling under the steps to prevent sagging in the future?

I'm in the process of doing my own fiberglass install as well. The best 2 ways I see backfilling a ledge is either flowable fill or like I did. Dig a hole on each side of it and proceed to shovel some stone in and compact it with a board. This process took me about 6 or 7 hours over a couple of afternoons. Its quite tedious but my steps and ledge are rock solid. If you do some research you'll see this is the place fiberglass pools most often crack so dont cut corners here. If you go the flowable fill route be careful as I've read you can float a pool with it.

 

[jimmythegreek]

If you never want it to settle order concrete amd pour the whole stair side in one shot with a quick and dirty form. Otherwise fill with small angular stone amd compact it in, sledgehammers amd small tampers work well. Wood is a no no anywhere on a pool or around it underground