Plastic vs Concrete tanks

Post Reply | Watch this Post

If it were my project, I would specify concrete. Both are adequate, but the ability of the plastic tank to withstand loading forces depends heavily on the installation, for example, proper backfill materials, proper compaction of that material, proper cover (depth of unit), as specified by the manufacturer. If the contractor installs in correctly, it is fine. Even if he is not completely to the letter on procedure, it may still be fine, since you may never put the maximum demands on the unit with regard to loading. But if the contractor is just taking advantage of the fact that he can buy it, deliver to the site in his pickup, muscle it in the ground with two guys, it is not the best way to go. Concrete is more forgiving to less than ideal installation practices, since it has inherent strength. Its more work ($) to install.

But a thou is a lot of money, if this is the way you go, I suggest you get the units manufacturer name from the contractor, look it up on the internet, and get the installation specs. You can then question the contractor before and during installation to make sure it is going in right. For example, chances are your native soil is not suitable backfill for a plastic tank. So in his quote, has he made provisions to bring in backfill material, or does he decide that later, and add money to your bill?

The town sanitarian inspects and approves the installation. I do not believe the sanitarians are usually well versed in topics such as soil types and compaction. Their soil knowledge really only needs to identify proper leaching field backfill, not structural backfill. The systems are backfilled after the installation, so they dont see it anyway, but the contractor may tell its all good because they inspected it. Contact the sanitarian to discuss what their inspection cover.

If you then feel comfortable with the plastic tank guy, use it and save the bucks. Good Luck.