I purchased a house with a 15 year old 1500 gallon concrete septic
tank. The home inspector found that the level of fluid in the tank was
6 inches lower than the outlet pipe, suggesting a leak in the tank,
since the tank had not been pumped in 2-3 years. Only 2 adults and one
child live in the house with a septic sytem capacity built for this 4
bedroom house. Baffles were normal. The leech field was in excellent
A contractor for the seller pumped out the tank and inspected it
revealing some cracking next to the gasket joining the upper and lower
halves of the tank. He repaired this with hydraulic cement, but felt
that the crack did not seem significant. He also said that there was
very little mortar left around the collar of either the outlet or
inlet pipe (can't remember), and also repaired that with hydraulic
My question: Do the findings of the contractor reasonably match the
severity of the problem (water level 6" below outlet pipe)? In other
words, is the low level of water usually in your experiences due to a
HUGE problem, or sometimes just due to small fixable cracks, like I
I don't know a whole lot, but I'll add my 2 cents. Without being
there, was the house sitting empty for a period of time? If so, a low
level maybe normal. If people lived in the house when the water level
was checked, where did all the water go? Is it wet aroung the tank? If
it isn't wet around the tank, and more than one person lived there,
there may be another escape route for the water. Look around, check
for wet spots in and around the yard/septic system. You can also get a
dye and put it down the drains, then run lots of water. The dye will
appear somewhere. Then you can decide what problems, if any, you
Your local health department may give you the dye, or come out and
check it out at now cost to you. But, you may be in for major repair
bill if they find something.
Inspected and repaired, probably OK. I had a similar minor repair on
mine. Concern would be solids reaching leach field clogging it up and
you say yours is OK. With change in house population field could get
wet if there are a lot more people in house. In our area, new
construction requires a 2nd leach field for backup.
Usually the problem is a septic tank that is too full, not full
enough. For arguments sake, let's say there is some opening in the
tank that is allowing some of the water to leak out. The water
has to go into the ground anyway, whether via the leach field or from
the tank leak. In years gone by, that was with a cesspool, which was
essentially a tank with no bottom.
The only issues I can see would be if the septic tank location is less
than the code distance from a well. Or if water is coming up at the
surface near the tank, etc.
Otherwise. I wouldn't worry about it.
Thanks for the replies.
The house has been occupied continuously.
Could you guys please clarify something for me. If the tank is 1500
gallons, shouldn't the water level in the tank ALWAYS be at the level
of the outlet pipe (assuming that at least 1500 gallons of water has
been flushed down the drains) if there is no leak?
You probably have a small crack at around 6" below the out-flow pipe
in the 2nd chamber. It's probably very small, since a large crack
would be obvious. Being small, the only thing that will leak out is
liquid, not solids. The water that leaks out will be absorbed in the
soil, just like from the leach lines.
One thing you can do is fill the tank, and time how long it takes for
the level to drop 6" without any water going into the tank. Obviously
you will have to do this when no one in the house is using water.
Knowing the dimensions of the tank and the time it takes for the level
to drop, you can calculate the leak rate. I'll bet it's very small.
You could probably find the leak by digging around the sides of the
tank to a depth of 8" below the tank top (bottom of the lid).
I wouldn't worry about it unless you see water coming to the surface
or causing a muddy condition.
Check to see if there are two tanks. My in laws house was like this
with one for gray water and the other a black water tank. The black
water tank was almost completely dry when it was inspected. Gray water
was used on the garden, lawn and fed into a small pond full of aquatic
plants. The septic tanks had never been pumped in 30 years and still
didnt need it. My father in law was very particular about what went
down the drain, no grease, no garbage diposal, no caustic chemicals.
He was green before it was popular. He just called it saving money.
I can remember reading many years ago, that some septic systems utilized a
syphon system in the second tank. The purpose of the syphon was to hold the
liquid until the second tank was full then the syphon would automatically
activate and empty the tank into the leach field. Checking the tank after
the syphon had emptied it would look like a tank that was low due to a leak.
I don't know when they stopped using syphons, if they ever did, in some
areas. I have never seen one in person, despite using septic tanks for the
last 55 years.
Would everyone agree that maybe my best bet would be to wait until the
tank fills with 1500 gallons of water over 3 weeks following the
pumping/inspection of the tank in order to see if the water level
reaches the pipe, as it should if the leak has been fixed?
Can anyone think of anything else bad that might cause the water level
to be low that could be missed on an internal inspection of the tank?
Im assuming that the person who inspected it is honest and there were
no other cracks. Can cracks in a concrete tank be accidentally missed
with internal inspection? I'm basically trying to decide if I should
hire someone else to inspect it.
Points about this not mattering as long as the septic tank is not near
well water (no well water, city water) are well taken. I also realize
that an overflowing tank is more of a problem, but the tank is right
next to the house and I don't want this stuff leeching into the
I guess. But that would have to be a huge leak to prevent the
accumulation of 1500 gallons of water in the tank over a 2-3 year
period. Plus we flushed a toilet and saw all of the water come from
the pipe into the tank.
How do you know it was "all"??? :) That would take a volumetric
measurement on both sides which undoubtedly wasn't done. Not that I
would suspect too much, just a point that you can't draw excessive
conclusions from simple observations.
As for the overall situation --
First is the question of the tank design, etc., ... was/is there a
siphon that could account for the permanent level?
Were any cracks/potential leaks that were fixed/repaired below the level
that could account for it? I've not read the whole thread by any
stretch but did see indication that what appeared to be most problem(s)
may have been at the level of the outlet which wouldn't have explained
the low level anyway. If misread that or that's wrong, ignore...
Is the house presently occupied? If so, it shouldn't take any time at
all for the level to reach the outlet level (in overall terms); normal
household activities will put quite a level of water down the drain in a
day or so unless there's some very stringent usage restrictions being
observed by the occupants. If so, observing the level should lead to
fairly quick conclusion as to whether there's an escape path somewhere
If it's unoccupied, and the tank is still open, I'd just fill it up w/
hose and other running water until it is at the outlet then watch to see
if it goes down from there for a period.
As for leak in exit line from house, how deep is that line and what's it
made of? Unless it's quite deep it shouldn't take much investigation to
discover (particularly since you say it's short) whether there's
waterlogged soil in the area -- even a probe rod should tell you the
answer of whether there's saturated soil or not close by.
That last holds for areas around the tank as well--if you can probe
deeply somewhere indicating soft ground, that would be telling of
leaking--of course if it's in area of repair above, that could/would
likely be old, not new.
All in all, if the house has been occupied and used in normal fashion w/
reasonable number of occupants and there are no visible indications I'd
tend to think it's not a major problem.
You might want to write in a clause in any contract that owing to the
circumstances any subsequent problems uncovered or becoming apparent
within oh, say one year, are to be covered 50:50 or something similar by
you and seller.
Yes, it has to be filled up after being pumped out in order to
determine if there is a leak. I am assuming you had it pumped dry. In
reality, the people who lived there before may have put another tank
elsewhere, or ran a line around the tank, or any number of
possibilities. Just because it would be illegal, doesn't mean it can't
Once the tank fills with water, then any leaks should show by water
coming to the surface, if installed correctly. The dye will tell you
that along with visual inspection around the tank.
Also, run your water for a few minutes and listen to see if water is
flowing into the tank. Like I said earlier, it may be directed to
Did you call the Health department to see if they would check it?
Didn't think so. :-)
Yeah, they pumped it dry to inspect it. The water is flowing into the
tank--we flushed a toilet and watched; so no extra lines or anything
The issue I have with using the dye is that there is no wetness around
the tank to begin with. If there's a leak, it's small/slow and it's
not showing up at the surface. Would dye still be helpful in that case?
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