Most septic companyies sell the plastic risers but they are expensive.

A 55 steel gallon drum and lid cut down works super duper and can often be found for free. I'm not sure if a plastic drum and lid will take the weight over time but my steel drum is still OK after 15 years.

Just measure what you need and fire up the torch or get the sawsall.

Every so often I read about someone falling through a rusted metal septic tank cover. Install a proper plastic riser and lid now, and avoid a tragedy down the road.

"Every so often I read about someone falling through a rusted metal septic tank cover".

I heard that too but my research showed those instances were when the actual lid on the septic tank was exposed. I never found one instance of a 55 gallon drum lid rusting through.

In case it is not clear, the riser merely gives easier access to the original cover on the tank. It does not substitute for the original cover.

The OP seemed to know that when he said "had to dig up the access cover. I would rather not have to dig it up next time. It is about 18 inches deep".

He's looking for no dig required access to the septic tank cover itself.

Maybe the setup on my tank is what the OP has in mind. It has plastic risers sitting over the open concrete tank ports, with a heavy plastic manhole cover on top of each riser. The covers are secured with drywall screws into the top of the riser. Alternatively, they can be secured with wire seals.

I am wanting to get rid of the current lid as well. It is a square concrete lid and has seen better days. Really who decided a square lid is a good idea. The guy that came to pump almost dropped it in the tank. I know if I try to remove to inspect I will drop it in the tank. So far I have found Tuf-Tite and Polylok make risers that would work. I guess I just have to see if I can get either localy or not. Thank you.

If the original lid will be gone, the riser has to be sealed to the tank to keep groundwater from getting in. Here's a picture of the risers being installed on my tank: