On Thursday, July 18, 2019 at 8:36:59 PM UTC-4, wrote:
On Thu, 18 Jul 2019 22:14:01 +0000, Hendu
m wrote:

I recently bought a home with a septic tank. I have never had one before so I
am trying to learn all I can. A couple of weeks ago we had a very bad rain
storm and sewage from my septic tank backed up through my basement drain. It
was very expensive to clean so I plan to take measures to prevent it from
happening again. From discussions with a couple professionals, I believe the
cause was a stream of water running downhill through my yard over my tank
covers. Enough water entered to fill the tanks and forced water/sewage up
through my basement drain which sits lower than the tank lids. My thinking is
that with some waterproof caulk (or Flex Seal (TM) ) I could make the concrete
covers waterproof in case of another severe storm. I know this is where the
tanks are accessed for cleaning, but the seal could be broken with a utility
knife for this maintenance. Is there another risk I am not aware of to making
these covers waterproof (and probably air tight)? Thanks for any
advice/suggestions



How far - is your basement floor - below the septic tank inlet ?
Do you have a basement " septic pump " ? for basement washroom
or laundry or water treatment .. ?
ie: are you sure that the basement drain isn't overflowing with
"other" septic-y water - storm sewer water polluted by illegal
septic hook-ups .. ? **** happens ..
If there is no possibility that the back-up is not from other sources
- then -
I would first look to resolve the issue of rainwater run-off -
- the grading of the area around your septic tank should divert
rainwater and mel****er around it. ... and also away from the
foundation, of course.
The drainfield should be able handle a good bit of excess - it
seems like yours does not .. you might want to consider that as
a future upgrade.
I've owned 3 homes over ~ 40 years - all with septic systems -
none have given me any cause for concern ; none have required
any remedial work ; just pumped out every 5 years or so - as a
precaution and for inspection ;

John T.

Kind of what I was thinking. I wonder how exceptional this rain storm
was or if the seller hosed him. Unless his yard has a whole lot of
downhill grade, a basement floor drain would likely not only be below
the level of the cover of the septic tank, but below the level of the
water in it, if it's high enough. Most, I'd bet a basement
floor drain is below the sewage water level if the tank is just half
full or less. Which is why they need ejector pumps for basement toilets,
drains, etc. as you have brought up. Homes I've been familiar with
that has septic systems, the line exited the basement half way up
the wall or higher, so you could not have a floor drain, sink or
toilet in the basement connected to it, without a pump.

Sealing the lid probably won't hurt, many of them are covered with dirt.
The sewer line is supposed to be vented back at the house, so air has
a way out. But I tend to doubt that the problem was caused by water
running in under the tank lid. It may have helped, but I bet most of
that water came in just from the flood over the drain field. There
are backflow preventers that can be installed on a sewer line and he may
want to consider installing one. Or if the floor drain is the only thing
in the basement, close it off.