Septic system upgrade

[GaryR]

The house we bought had a tank and field undersized for the number of bedrooms, according to the health department. Sellers agreed to pay for the upgrade. It took months to get the work scheduled but this week it happened. All those big machines in the yard brought out the seven year old boy in me! What a mess! But it was interesting to see how they upgraded the tank. Exposed the old tank. Pumped it out so we could use it while they broke the line to the field and dug a big hole for the new one right behind the old one. Set the new tank in place. Crushed the lid on the old tank and collapsed it in on itself. Filled the old tank with gravel. Connected the pipes to the new tank. Back filled the dirt, with some left over to improve the grade around my shed. They added another line to the field, too, but that wasn't so interesting.

Old tank exposed, new tank dropped into place.



New tank in place. About to crush the old tank.


All done. The field is back and to the right of the shed. The line from the tank to the field goes right under the shed. Just missed it when we augered out the holes for the piers.

 

[TrimTheKing]

What's in the field Gary, the soakaway?

 

[duke]

Interesting rig for unloading the tank.

 

[GaryR]

What's in the field Gary, the soakaway?

It is called a Presby system. Very common locally especially in new construction. Basically fabric coated perforated tubes set in sand.

 

[Cabinetman]

How did they collapse the old tank Gary? And did they do that to prevent it collapsing in on itself in years time?
Ian

 

[GaryR]

How did they collapse the old tank Gary? And did they do that to prevent it collapsing in on itself in years time?
Ian

They just bashed the lid in using the bucket of a mini-excavator (Caterpillar 305E). And yes, I think that was the logic. The tank was 60 years old. Perhaps it would last a long time still, but better safe than sorry.

[edit] Thinking again, the tanks are designed to be nearly full of "liquid" in use, and that liquid can resist hydraulic forces of the surrounding soil. If the tank is pumped out that weakens the walls and makes self-collapse more likely. Like an empty swimming pool. Better to fill the tank with gravel and dirt.

 

[Cabinetman]

They just bashed the lid in using the bucket of a mini-excavator (Caterpillar 305E). And yes, I think that was the logic. The tank was 60 years old. Perhaps it would last a long time still, but better safe than sorry.

[edit] Thinking again, the tanks are designed to be nearly full of "liquid" in use, and that liquid can resist hydraulic forces of the surrounding soil. If the tank is pumped out that weakens the walls and makes self-collapse more likely. Like an empty swimming pool. Better to fill the tank with gravel and dirt.

Ah yes, that makes perfect sense.
Ian