Cost will be the factor in whatever you do. If you have someone come out and remove the dirt from around the tank you can float the tank by putting water in the hole you can then pump concrete under the tank or you can pour concrete Thur the water to under the tank with a plywood four sided chute.

Good luck

pull the tank and move it !

The soil there is not solid enough to hold it or there is water inflitration around the tank allowing it to sink.

Either way the tank has to come out.

Or Pull the top off the tank and fill it with dirt and install a new one in a better location.

Nebraska ? Are you near that large fresh water aquafur up there ?

Hello nebraska:

You say you laid a field and put the septic tank in it?

Had there been a septic tank in use around your place before?

If the tank is in new ground or ground which has been disturbed by digging, together with the fact you have a high water table, have you had rain or is there any flow of water at all through the field, maybe below the surface? Because if you or a place which has a 'run-off' even several miles away, flows through the field or, if the natural levels are such that water may lay in the field, the tank may be floating right now, or trying to!

If however the soil is a clay type the tank could be slipping around trying to find grip to allow it to settle?

Is the tank in a hollow?

Is the ground dead level?

Where will the water table reach in the rainy season, I mean how far up the tank?

There could be a danger that any overflow can find its way back to your house? Unless it is raised. As long as it is not floating and the land does not slope at all toward your house, or the house and tank are not both in a slight dip in the ground, any run-off will be taken care of by the soil bacteria and there should be no smell. There is no need whatever to 'sanitize' the area!!!

It is never a good idea to have a septic tank on low ground, as the tank itself can and will flood. The more the ground is soaked the deeper it will sink and after a while will not be use-able. All tanks I have dealt with have been on a small plateau on a hill and this allows plenty of run-off if it overflows.

I do not think 'floating' the tank and concreting round it will work as if there is an aquifer, the whole lot tank and all could slide gradually downhill if it is on a slope.

I know there is often not much choice as to where these tanks are placed, and it depends on whether it is fibreglass or concrete as to the solution. Perhaps finding a new place and digging a lot deeper before filing the bottom with an almost dry concrete mix, by that I mean not runny, could work. But you have to figure out whether the cost to get the original one out is going to be worth it. If not, as has been said just fill it with soil and start again.

On one sight I worked on we could not seem to reach 'hard ground' so we used 6"x6" oak posts and pile them around the tank leaving the top of the posts about 2' below the ground. There was aggregate only, underneath. And it has never moved. The thing you have to watch is that the posts are barely touching the tank. If it is fibreglass it could split.

Good luck. There is no easy way round this. But, you may be able to pump any slurry out and cover it with soil and then dig the tank out and use it again.

The contents of the tank when full will weigh 4.5 metric tons. And if you want to move it you will have to empty most of it then you can use a normal gravel lorry crane to lift it if all the soil is cleared around it. It mat also be apparent why it has moved as you dig it out?

All tanks I have seen have had a chalk or flint base/foundation which, to allow extra drainage has several tons of shingle in the whole before the tank is inserted.

I hope to find a sump pump small enough to fit into the 4" outlet pipe for a temporary fix. I can access that through a manhole in the tank lid. Does anyone know how the tank can be leveled again without removing it and resetting it again?

Sure but how long do you want to be dealing with this project; you could be fixing it into retirement.

It is probable a mound style tank is recommended in your area to avoid this issue of yours. I don't like the mound style because they can be problematic but not of the sinking type.

But if you insist then dig a hole on each side of the current tank location big enough to get the equipment into and possibly under the tank. Lift the tank and maybe dig deeper to accommodate compaction equipment so you may then reset the tank appropriately.

I strongly recommend your thoroughly consider an alternate method to restore the integrity of your tank placement.

You could as was suggested in another post dig an alternate hole.

GA

Contact the party that installed the unit and get them to fix it properly.

Usually no. The tank supplier is not the one who decides where it is set. They don;t dig the hole either. That would be the contractor/ builder very seldom will even the plimber accept responsibilty for setting a tank.

One thing this man better realize that the tank does not weight as much as his house !!

THE HOUSE COULD BE THE NEXT THING SINKING IF HE IS NOT CAREFUL. He could be setting on or near an underground stream that is keeping the ground wet and allowing things to sink.

I would go back and re check who did the site selection for the home and what checks were preformed to see if the site was stable.

Good morning nebraska. As others have mentioned, what was the soil strength prior to installing the tank? How much pressure per square foot does the tank and its contents cause? Is the soil strength adequate to support the tank?

The IRC (International Residential Code) says that in areas likely to have ...unknown soil characteristics, the building official shall ...require a soil test. In lieu of a complete geotechnical evaluation (test), the load-bearing values in Table R401.4.1 shall be assumed (the worst of which is 1500 psf). Does your septic tank induce more than that?

Is your septic tank steel, fiberglas, or concrete? What are its dimensions? If concrete, some are built with a horizontal seam (construction joint) maybe a foot from the bottom (IPSDC p19). This seam (keyway) might have an isosceles trapezoidal cross section, concave upward. If during installation, a bit of gravel got into this groove, liquid could begin migrating to the underside of the septic tank, undermining the integrity of the supporting soil.

I would look to your installing contractor to fix the situation, as he was being paid to look out for these types of possibilities and recommend to you various remedies prior to starting the job. As others have stated, it appears the best solution is to remove the lid and tank, and properly prepare the receiving soil for the tank. This may require a rebarred concrete base. You may want to hire a soils or structural engineer to assist with this task. If your installing contractor balks at helping you, a complaint to your local building official may gently prod him into assisting you.

Try to find if there is a mud-jacker or pile jacking contractor available in your area and see if they can provide recommendations. Sometimes lean concrete mixes can be used to give some strength to unsuitable soil conditions.

Get advice from at least 3-4 local contractors who know local conditions. The good ones will have some agreement as to cause and workable solutions.

Thanks for the advice. I'm going to follow through with Ried's advice and see where I get with it. I hope the tank is done sinking and can now be jacked up in that manner. The dwelling has been setting here since about 1965 high and dry. The topography is level, the field is fine, it's just the leaning tank which was perfectly level when we installed it. I did not have a contractor. I just hired an excavation contractor to do the digging and installed everything myself after giving up on plumbers who were too busy to even come out here and give me an estimate.

Thanks for giving more details.

Now i bet the tank sank a little and you did not see it. The pipe cracked going into the tank and then leaking water from that cracked pipe softened the ground under the tank and it sank suddenly.

I had the happen once but the tank never tilted. Guess I was spared that nightmare.

Check the pipe comming fromn the house around the footer or block work for a break too.

I believe you are going the right direction, they lift whole slabs and whole houses that have sunk down in New Orleans by jacking them up using concrete pumping I have had some experience pouring concrete under water and it is easy and cheap, ask them about it.

Mike

Hello nebraska:

you have some good advice there!

Can I ask the physical size and shape please? I have only dealt with round tanks.

With it being there for only a month there probably will not be that much in it and, depending on its shape, it should come to a point where it cannot sink any more? In which case you re-work the ground around it.

If it is only part filled, try filling it with water so it compacts itself. Pump the water out after a few days, lift the tank out and put a concrete base in raised at the edges to support the tank bottom. Replace the tank and, if as I say the tank has compacted the ground underneath, as it should, with the concrete it should move no more. You will have to relay the sewer pipe to it of course.

Good luck!

The tank, including lid, is 99" long, 62" tall, 67" wide, the walls and bottom are 3" thick, it holds 1,017 gallons, the inlet is 7" down from the top, and the outlet is 10" down from the top. It took two of us 10 days to fill it with sewage. I'll dig down to the inlet and see whether it is leaking at that point. There is a good rubber seal and I had a hard time shoving the 4" sewer pipe into it. The top of the tank is just barely underground.

I'm still going to rig up a temporary sump pump hanging under the manhole at the outlet to get me past Thanksgiving because I'm having company that weekend and I don't want it to crap out on me then. It will be hanging in the clear effluent and drain into the outlet. I looked at Home Depot and Menards today and couldn't find a small one with an interior switch. It only needs to pump 100 to 200 gallons per day.

I can easily get someone to pump it out but we've had quite a lot of rain since I installed it and the ground is too soft for a heavy truck to back up to it or for heavy equipment. I don't want the ground all tore up. I may have to wait until the ground freezes now.

Hello nebraska:

I have only ever seen round ones. Anyway you say you are taking Reid's advice. Good luck. It is not something you want to do twice, right?

With regard to the emptying of the tank and the slippy conditions. You may have these, we have square concrete blocks, which are about 4" thick and a foot or so square. In the conditions you mention they would be ideal as a 'road' from the local road to the tank. These bricks have small holes where after laying you rake over with soil and sprinkle seed on. After a few weeks you will hardly notice them. Just a thought. Or just leave the local grass to self seed?

Take care.......

Hi nebraska,

www.northerntool.com search 'dirty water pump'

Thanks Wire.