Septic Tank Anchoring
Septic Tank Anchoring
(OP)
I'm looking for ideas to anchor a septic tank. The tank is within a VE zone and therefore subject to buoyant force. The project is in florida (no seismic).
I have heard of using auger cast piles. We specify piles for pool shell holddowns all the time.
The contractor is sugesting using "long screw anchors, hand installed, with metal straps attached to the tank".
Also the scour elevation accoding to DEP is 5.2. Grade elev = 13'. Does the achoring system need to go beyond the scour depth? I have heard that if we design the tank to sink, I can use a shorter anchoring system. It makes sense to me, what do you think?
Thanks
I have heard of using auger cast piles. We specify piles for pool shell holddowns all the time.
The contractor is sugesting using "long screw anchors, hand installed, with metal straps attached to the tank".
Also the scour elevation accoding to DEP is 5.2. Grade elev = 13'. Does the achoring system need to go beyond the scour depth? I have heard that if we design the tank to sink, I can use a shorter anchoring system. It makes sense to me, what do you think?
Thanks






RE: Septic Tank Anchoring
RE: Septic Tank Anchoring
Mike McCann
MMC Engineering
RE: Septic Tank Anchoring
Next, a septic tank must be kept full of water all the time to work at all. If your water table is going to be as high as the freeboard height of the tank, you've got a problem that a septic tank won't solve.
Next, if you are pumping to an elevated drain field, it's the wet well you have to worry about floating, not the tank.
Outside that, use additional concrete ballast as Mike and par060 noted.
RE: Septic Tank Anchoring
RE: Septic Tank Anchoring
It is possible to pump directly from a septic tank to an elevated drainfield, low pressure sewer, etc. using a filtered pump vault in either a single or two-compartment tank. Orenco makes a fine product to facilitate this:
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In the event that a wet well is being used, the septic tank still needs to be protected against flotation. Yes, it's usually full of water, except for when it's not (e.g. during periodic maintenance pumping). They'll come right up out the ground like a submarine next to the pumper truck if the ground water is high and there isn't adequate cover or concrete on top of the tank.
All that said, for the original poster, your client should be sure to use a high-seam tank to reduce the chances of infiltration/exfiltration. Then just make sure the top is thick enough to provide enough weight (along with the proposed amount of cover on top of the tank) to keep it in the ground.
Vacuum test the tank on site as well to ensure it's watertight, especially if they'll be pumping out of it.