Seal or cover a septic tank lid

July 12, 2010 7:27 PM

Is it safe to tightly seal (or cover) the lid to the "pump tank" in my septic system?

I have a two tank septic system. The first tank is the main septic tank, which then drains to a pump tank. Once enough water has accumulated in the pump tank, the liquid is pumped uphill to the leach field.

The pump tank is new and has a plastic lid that isn't quite air tight. Because of this, it occasionally smells around the tank.

Is it safe to completely cover the tank lid with dirt, or perhaps seal the lid with caulk?

posted by foggy out there now to Home & Garden (5 answers total)

It is probably safe, but I wouldn't do it. If it were a gravity outlet, I wouldn't think twice. With a pump, you are either putting a slight vacuum on the secondary tank, or you are pulling air through your house sewer system. In the latter case, you may be just pulling against the roof vents or, if they are clogged, against the traps. In either event, you are adding to the work the pump has to do, so it is likely to wear out sooner.

If the tank is well away from the house, you can put a chimney on it to vent the smell up away from ground level.
posted by Old Geezer at 7:42 PM on July 12, 2010

Smells? Smells like what? Are you sure it is working properly, I have never had a smelly septic, but then my old system drained out into a trench (yes it did overflow sometimes, but I never found out from the smell). Currently I have an aerated treatment plant, and it is totally smell-less (except for a hint of chlorine).

If in doubt, dump a kilo or so of mince down the loo, or directly into the first tank. DON'T break the scum on top, the bugs worked hard to put that there and it is important as it keeps the air from the biological processes going on in the effluent. You should have an inlet with an opening that allows stuff to be dropped directly into the water. I don't suppose I have to add that it is preferable to avoid being splashed when you do this...
posted by GeeEmm at 1:55 AM on July 13, 2010

According to a coworker who specializes in septic/sewage systems designs:

Cover the pump chamber lid, 2-3 inches of topsoil, patio stone, woodchips, whatever you want, though I wouldn’t caulk it. All you have to know is that it should remain accessible, by you or by the guy who may have to work on it. If you can't find it, you can't fix it.

Anything you cover it with has got to be semi permanent.

Another idea to consider is to add a carbon filter on tank(s). They now install them to cut down on odour. That sticks above ground too but it don’t stink like sheet anymore.
posted by wennj at 5:51 AM on July 13, 2010

Cover it? Well OK, as long as the lid is above ground level, ie no ground water/run-off can get in. But you will still need to be able to find and access the inspection covers.

As far as filtering the vent, you have a choice - fix the smell (eg a filter - personally I have not heard or experienced these so I can't comment on their efficacy), or fix whatever is causing the smell ... For my money, the smell is telling me when I have a problem, so I would not want that 'alarm' tuned off, but ymmv.
posted by GeeEmm at 9:49 AM on July 13, 2010

Response by poster: Thanks everyone.

To clarify on the smell, it isn't your standard run-of-the-mill septic crap smell. It's more like sour water - sort of like a marsh at low tide. It's post-septic tank, so the liquid is clear but still sort of smells. The amount of smell is also very slight; a few minutes of stink every few days.

If I smelled it in the yard, it wouldn't be a big deal. The layout of the land seems to funnel smells up the hill into our open windows. (Don't even get me started on when the deer died at the creek below us. It was unbearable until 20 turkey vultures showed up for dinner.)

The lid is 3-4 inches above ground, so I'll build up a little hill around it and top with as little dirt as possible. If the smell persists, I'll call the professionals back out here.
posted by foggy out there now at 12:37 PM on July 13, 2010