Serving Grass Valley and the Surrounding Areas | 530-273-4605

Hole Preparation

Septic tank

Trust Us for Quality Septic and Pump Tanks

Merrill and Sons has been offering quality concrete products for 60 years. Use our sturdy, quality concrete septic and pump tanks to construct your septic system. Take a look at the installation instructions below.

Septic and Pump Tank Excavation 

The hole has to be dug, graded and approach prepared prior to the delivery truck arriving on-site. The hole must be dug according to the listed hole size with straight and square sides. The hole sizes allow for a 12-inch cover. 
Any loose dirt has to be removed. If the hole is over-excavated, do not fill with loose soil. Use sand or pea gravel over undisturbed ground to bring the floor to the proper grade. All protruding roots, rocks, pipes, or obstructions must be removed.

Septic and Pump Tanks Need a Solid Base

Tanks need a solid base with no loose fill or mud under the tank. If a solid base can't be realized because of ground water or mud, the hole must be over-excavated and filled with coarse rock to provide for a solid base for the tank.

Trust Us to Ensure Proper Base Preparation

Any cracks that are caused by settling or improper base preparation will not be warranted. Water needs to be pumped out of the hole until after the tank is set. The tank will only be level if you have a level base to set it on. 

The base should be level and sized the same as the hole dimensions with a 1-inch concave depression tapering down to the center of the hole. This will support the weight of the tank on the tank walls.

Septic Tank Measurements

Septic tanks should ideally be set with 12 inches to 18 inches of soil cover with a maximum cover of 36 inches. The maximum cover on tanks is 36 inches. Do not drive any vehicle or equipment on the standard tank. Any cover over 36 inches will require a traffic-rated tank.

Although heavy, concrete tanks will float. If ground water or rainwater gets in the hole around the tank, precautions must be taken to prevent floating. Putting 24 inches of water on both ends of the tanks will help prevent floating.
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Be Mindful of the Tank When Backfilling 

Native soil is usually adequate when backfilling. If using the loader or backhoe to backfill, care must be taken not to hit the tank. Rocks that are larger than 6 inches should not be allowed to hit the tank. Do not drive on the tank at any time.

The pipe seals that are on the tanks are shipped folded inside out. To install your pipe, from the outside of the tank, reach inside the seal, grab the inner lip, and unfold the seal. Chipping concrete flashing around the outside of the seal may ease the installation of the pipe.

We are a distributor for Orenco Systems, Infiltrator Systems and Geoflow

We have been providing quality concrete products for 60 years. Contact us today for all your septic system needs.

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