Positioning a sump on a floor and compensaring for not level floor

[SilverPhoenix]

I have a rather odball question regarding positioning my sump under my tank.
My house is single story on top of concrete slab. Atop that is some glued down enginered tongue and groove wood flooring, about 3/8" thick.
I have a wooden stand constructed of 3 x 2x4 at each corner supporting 2x6 cross beams running the 6' lenght of the tank.
Probably overkill but to compensate for any potential sag I have 1.5" angle Iron atop the 2x6 beams. 4" steel beams we just rediculously pricey.
My issue is that the bottom of the DT will be at 42" which puts the bottom of the 2x6 at 36 1/2" above the floor.
My sump is 25 1/2" high leaving 11" clearance between the top of the sump and the bottom of the beams.
My planned skimmer is 10 1/2" at its narowest dimension.
I failed to account for the fact that there might be a significant bow in the concrete slab under the tank.
When in place there is about a 3/8" gap between the floor and both ends of the tank. The middle 2 feet if the tank rest solidly on the floor.
Obviously I know that this is unacceptable from a stress standpoint on the tank.
Unfortunately I have left myself with very little leeway to compensate for the bow in the slab.
Has anyone had any experience with using self leveling agents in order to place a tank directly on the floor?

If my calculations are correct (est 2800 lbs of weight over 192 linear inches of rim at aproximately .75" width for a total of 142 square inches of contact translates into roughtly 20 psi pressure being applied to any given square inch of floorint under the tank. for the sake of safety I believe I have over calculated the weigth of the tank and under estimated the footprint of the bottom rim of the tank. I have also not included the footprint of the 2 cross braces in the middle of the tank.

Would I be better off removing the flooring under the tank and leveling straight off the slab?
I left the flooring there under the premise that, if I move and dismantl the tank I hypothetically might not have to redo the floor under the tank or at most might only have to refinish it.

My project has obviously stalled until I can find an adequate remidy for this issue.
I have explored using some construction epoxies that when cured have a strength of about 2000 psi to build up a level ledge to support the footprint of the tank but they have been too cumbersome to work with properly. I remember seeing self leveling flooring agents on this old house or some other show years ago and know that they exist but havent had much luck in finding one in the stores. or at least one that any of the employees think would have a chance of workign for me.

I have even considered using an epoxy resin clearcote agent that I used years ago tha tis supposdly equivalent to roughly 40 cotes of polyurathane but I havent got my hands on it to see what it's cured compression strength migtht be.

Any suggestions would be greatly appreciated.

Thanks

 

[jerry26]

If your building on top of the hardwood, it might just be warped and bowed. especially if its got bending luan under it. I personally would just build straight off the concrete. I work at a place that supplies stuff like that to construction sites and ill ask around for what might be good. But i can tell you right now that floor will have to be at least temporarily removed. Or you could take a piece of high density foam and shave it to match the curvature of the floor. But still, ive seen what standing water can do to those floors and wouldnt do it myself but i mess with stuff so much im bound to miss some water when cleaning up.

What is the actual length/width of your stand?

 

[SubRosa]

Are you certain the bowing is in the floor and not in the stand? I built a stand for a 180 a few months back, and when you're working with stud grade 2 x 4s you need to take the crown of the wood into consideration. When the tank sat empty on the stand, I had the same situation, but when filled it sat flush.

 

[jerry26]

So i talked to the guys at my work and they said to just use a regular ol concrete patch. But like i expected theyre saying youll have to form it up. You wont be able to just dump it and have it level itself. The self leveling agents will spread evenly throughout the low spots until its finds itself level, which means it going to spread until it hits another high spot. Since youre just trying to level a small area, itll have to be formed.

 

[SilverPhoenix]

Jerry26
The actual stand is almost 80" long by 24.5" wide. This is to allow for the 72" long tank to fit underneath it.
I think I'll bite the bullet and remove the flooring before trying to level it.

If nothing else it will give me another 3/8" inch of breathing room to level the floor and still fit the skimmer into the tank once assembled.

I'm prety certain that it is the slab itself that is bowed as the flooring is 3" wide planks and only 3/8" thick and glued to the slab.

To account for a 1/4" difference over a 3' run the material in the center would have had to have swelled to almost twice its thickness and I don't see any signs of that.

Also I have 1200 sqft of floating flooring that was just installed that shows other signs that the slab itself has dips and rises as there are a couple of spots that flex as the slab dips underneath them.

Thanks also for enquiring with your co-workers.

 

[SilverPhoenix]

Sub Rosa
I'm certain the bowing is in the floor and not the stand as the sump rests directly on the floor.
As for the stand, the tank is resting on 2x6s not 2x4s although I realize that 2x6's are also subject to the crowning effect.
I also made certain that, whatever crown there was was pointing up in order to minimize potential sagging in the future.
I'm not certain what sort of grade I used but I am prety certain it was higher than your standard stud grade. It looked more like an exterior finish grade.

Thanks anyway.

 

[SilverPhoenix]

jerry26
The area is small but it is basically formed in. The stand rests on 2 2/x6 "feet" for lack of a better words along the the ends of the tank.
There is a 2x4 along the back wall of the tank forming the base of the back wall of a bench on the other side of the tank.
so 3 sides of the area are already boxed in by a 1.5"high wall.
I can basically caulk up any gaps between the stand and the back wall to prevent oozing and runout of the agents
and then all I would need to do is provide a front retaining wall for the form in order to create a square box form to contain the leveling agent.
My one question would then be, are the leveling agents strong enough to support the tank if I remove the front wall of the form after the agent has cured.
I know pushing down on something causes it to want to spread out sideways so if the material is .25" thick at it's corners, would that compromize the strength of the material eventually leading to failure of the material.
Although technically if I am only correcting for a .25"curvature and the glued down flooring is .375" thick I guess the flooring itself could potentially act as a retaining wall post pour.
Just want to know if I pour thicker than the flooring if that would be a problem.

Although , It's not like I'm talking about building a 3" raised platform here, I'm really only looking at raising the corners between .25 to .625 inchs.
.25 should theoretically bring the corners to level with the central bow of the slab but will leave a pocket in the floor that the tank would drop into and that might make it dificult to pull the tank out if it needs to be serviced in the future.
.625 would level the area out with the highest point of the flooring but would leave a .25" "cliff face" to the material that I might be woried about eroding over time and causing the tank to fail.

Again, I believe I am talking about less than 20psi of force at any given square inch under the tank.
but 180 gallons is not something I really want to triffle with, if you know what I mean.

Can you let me know what they think of that Idea?

Thanks again.

 

[jerry26]

I had asked them if a thin layer would have a problem with chipping over time and they said since it wasnt a moving object it should be fine. They said at the high point where its thinnest you may have chipping, If you dont fill over the hump youll have to feather the edge(whatever that means). The cure strength of the material we were talking about as an example which was (high dollar) ardex k 15 self leveling, and it had a 28 day cure strength of 4100 psi which is slightly higher than actual concrete. Alot of the concrete patches are designed to be spread thin so theyre a little more resilient than one might think.

I did some double checkng and the product we were talking about is designed to be spread up to 1 1/2 inches thick, just to give yo an idea of how thin its designed to be. This particular product does call for a primer for proper adhesion but They said in a small area like that with a non moving object, they wouldnt worry about it. apparently the stuff we were talking about is designed to be spread real thin and is designed for people to be walking on and stuff rolling over the top.

But they did say, that sealed concrete is a deal breaker. It will not adhere properly. Since thats an interior foundation that under a flooring, its likely not sealed. If its glossy, its sealed.

I was thinking about the front of the form thing, if you used a piece of trim or something you may be able to leave it in place and keep it nice looking.

 

[jerry26]

I keep forgetting to mention there is another option, you could always grind the high spot down. Dirtier, harder, the grinding bit is expensive and its more hands on but its the best way in my opinion. No worries about chipping and it doesnt matter if its sealed or not and theres no ledge if you decide to put the flooring back. If all thats contacting the ground is a perimeter of 1 1/2" thick 2x6's, you wont actually have to grind much off(Just the perimeter). Just take a six foot(assuming thats the width of your tank) level or a shorter one(probably want to use one thats at least 3') attached to a 2x4 thats not warped and just keep checking until the floor is flat. Just start at the highest point and work downward(not into it from the side). I cant say exactly how long itll take but i know the bits we sell will shred concrete and the small one is like a 3" diameter. But i think it costed like 50-120$.

 

[jerry26]

i think i may be.confused. is your stand kinda u-shaped? with no beam running the width at.the bottom?

if you just have feet on the ends, id be worried about it collapsing sideways. but if you say you built it right im not gonna critique it.

if the sump is sitting directly on the floor(assumed level), it will have no problem with spreading or chipping. the weight will be distributed over a large area.

the only problem i see that may cause chipping is if the hardwood is used as a retaining wall. the up and down motion that hardwood floors have may wear it and cause eventual chipping.

if you used a leveling agent then put the flooring back down i dont think youd have any problems since there would be so much weight preventing the floor from moving. but im sure you realize there may be a weird lookin high spot there.

if you put it directly on the concrete, id say cut a.little extra off.the hardwood and put pieces of baseboard trim around it to act as a retainer and prevent the hardwood from contacting the.patch. the front would be easily removed for servicing. other than sliding a piece of plywood in there or patch filling up to level with the floor, i.dont really have any ideas to raise it and avoid the lip.

sorry about the random periods, im on a tablet and i gave up trying to correct them all.

 

[Choff]

My rsm 650 (150dt + 25g glass sump) stand is actually propped up on leveling feet. There is either 2 or 3 rows of 5 or 6 rubber capped metal feet.

Point being the entire run of your stand does not need to be flush to the floor.

Wouldn't it be easier just to shim the stand? If you are worried about the shims compressing over time, you could use metal or get shims made from hard wood.

Seems like a lot less work than what you are planning.


Sent using Tapatalk 2

 

[jerry26]

You definitely could do that. I personally am not a fan of shims but they would do the job.