OK to Cover Septic Tank Cover?

[ski]

Our septic tank's concrete cover is exposed, flush with the ground. It's a very old tank, probably dating from the 30's or 40's. We recently had it pumped out by a seemingly knowledgeable guy who said that the tank appears to be a home-made job, but that it was constructed remarkably well and has a design comparable to -- if not better -- than anything he's seen which is more up-to-date.

The only problem with our septic tank is that you can occasionally smell sewer gas. It's likely that it seeps out from some small chinks along the edges of the concrete manhole covers where they don't mate perfectly with the surrounding concrete of the tank cover itself. And the whole thing doesn't exactly look attractive, so with the idea of preventing the smell from escaping and also to make it look nicer, I asked the septic man if it would hurt anything to lay topsoil and grass over the septic cover. He said that would be fine as long as I put some kind of planking or thick plastic sheeting over the manhole covers so that dirt didn't enter the tank through those chinks.

We'd like to do this but I'd like to get a second opinion. Will covering the tank cover with dirt hurt the system?

If pictures would help you assess the situation, let me know and I'll reply with some links to pictures. Thanks a lot!

[suemarkp]

Not a problem. Every tank I've ever had was buried under dirt. Make sure you mark where the covers are (perhaps with small round patio pavers), or else you'll be removing a bunch of dirt next time you pump to find the lids. Most pumping companies here expect you to uncover the lid when they come to pump, or know exactly where it is and it can be exposed with a few shovels of dirt. If they have to hunt for it, they charge you by the hour.

[mdshunk]

If the lid is very old, please evaluate it for it's strength and possible replacement before burial. Nothing would be worse than mowing the grass some day, and having a cave-in. I've seen folks just put something decorative on top, like a large planter or bird bath.

[ski]

Thank you suemarkp and mdshunk for your replies. md, your point about evaluating the strength of the cover is well made. I would never have thought about that aspect of it on my own. TYVM!

[joed]

You can't seal it either. There has to be an air vent. If it is totally sealled the water and "stuff" won't be able to flow into the tank if the air can't get out of the tank.

[suemarkp]

I've always wondered about that, but none of the tanks I've ever had has a vent that I can find. It is supposed to be an anerobic system, which means not exposed to the air. But, how are things supposed to flow without an air vent?

All I can think of is that your house main sewer pipe vent still kind of works for the septic tank unless the inlet pipe is totally full of water.

[Phil H]

I have seen countless septic tanks and have never seen a vent. When water enters the tank, an equal amount leaves. I imagine any entrained air and any gas formation escapes through the building's vent or through the drain/leach field. On the otherhand, if the septic tanks effluent (outflow) is pumped to a remote drain field, the vault or sump for the pump must be vented.