Question from homeowner on adding risers to a concrete lid. I have a concrete tank (estimated at 1,500 gals, circa late 70's) and the top is about 3 feet below ground level. The lid is composed of a series on concrete “planks” that are the width of the tank long and about 2.5 feet wide. So the planks sit laterally on top of the tank to form the lid. I am unsure how many planks are in total (since the entire lid was not exposed when it was recently pumped), but I would guess four planks total.

Since the lid is so deep and pumping it made a real mess in my side yard from digging the area to expose the first plank, I wanted to add risers. The septic company wanted $1,500 to add two risers at both ends; but I wanted to explore some options. How does one add a riser to the plank units? Or would I go about getting this manufactured (precast company, etc)? I would guess the entire plank is replaced, but since they are only 2.5 wide, the riser diameter presents a problem. Thank in advance.

Don't take this wrong- I highly recommend having a riser installed to allow access to the tank. That being said, I don't think that the average homeowner is up to the task of installing it. There are several factors in play. You need to have a riser that is larger than the current lid or has the same inside diameter as the opening you have currently. Then you need to consider the amount of weight that you are adding to the rim of the current opening. If you are adding too much weight, you could cause it to cave in. Also consider the weight of the riser itself when you would be installing it. Do you have the capability to set it properly? If you can handle the challenge, then I suggest contacting a local concrete vault or fabrication company; they can get you what you need as far as a riser and new tank lid. This forum isn't for pricing, but I can tell you that in my opinion, adding risers, lids, and installation to two spots doesn't seem unrealistic.

The weight of the new lid and risers will be less than the weight of the 3' of dirt removed. The company that cast the original tank and lid is probably in your area if still in business.

Usually, the two end sections have "square" access openings above the baffles. if so, a section of 6" ABS or PVC will cement into the opening with female adapters and plugs on top.

Unless you installed it, you are making it up as you go. Septic tanks aren't made to specific dimensions anywhere. I have seen concrete in varying sizes, shapes, and thicknesses. I have found them made of clay, steel, and plastic. Every concrete vault manufacturer has its own design, lid size, and placement.

I can tell you what I did. It worked for us. Our septic tank was 1200 gallon and concrete. We had 3 slabs, each having 2 loops of re-bar for lifting them. Each slab was about 3 ft x 5 ft and were laid side by side. I did exactly what you want to do. I made a frame using 2 X4 and plywood under. I was able to obtain a 3 ft piece of 20 inch PVC pipe. I secured the pvc inside of the form and secure everything with rows of re-bar. I oiled all of the wood and used plastic bags as a liner to keep the concrete off the forms. My neighbor was pouring a slab of concrete in his drive was and he had some extra material. 3 wheel barrels and I pour the concrete into my form. I added 2 hook loops and let the concrete dry for 3 days before I removed the forms. The slab with the 3 ft stack was lifted and place on the edge of the septic tank. We back filled with dirt and sand to compact the area to almost the top of the stack. I went to a specality shop that sold septic system supplies. Only then did I realize that the industry made 4 inch x 22 inch, stackable flange pieces that snapped together to form any height. I purchased a 22 inch dome cover and placed it over the 20 inch pvc pipe. It worked perfectly and allowed me to add an additional 3-4 inches of dirt over the cover. No one walks on the cover. Removing 3-4 of dirt is a lot easier to do and repair. I'm happy and that was over 3 years ago. That's 3 snowy winters.
Best Wishes

Maybe so where you are, but here, almost EVERY tank, regardless of who made it has an access port above the baffles. They also usually have a large center port, but no one installs a riser at that one.

Many of the older tanks here don't even have baffles.

ok Thanks. All good ideas. I had thought about pouring the lid myself, and may do that. But I will speak to a tank manufacturer in the area first. I have not checked the middle of the tank for an existing access hole but will do that as well. 3 feet of Georgia clay is not much fun. Thanks. Kratman.



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