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denemante 01-09-2012 03:34 PM

good working septic fields flooded more easily?
Hey all,

After a recent inspection of my septic tank and fields - I'm in great shape. However - during times of heavy rain (sometimes combined with extra water use from the inside) - the system "slows down". Basement toilet won't flush. I give it a few hours - and it works.

I've always had this issue - I posted about it - and everyone thought my fields were done, but now I know they are fine.

So my question - if my fields purge off water perfectly (and aren't "clogged") - it would stand to reason that they would take on water just as readily. So if we've had 3-4 days of solid rain - the ground around them would be saturated. With continued use of water from the house - the tank would fill - and there is no where for the water to go. I give it a little time, and water again begins to purge off. My neighbors report the same thing.

I've also heard and know you can't overwork/flood a septic system.

Does this all make sense? I mean - if in fact my system got a clean bill-of-health - yet I experience this "slowness" during rain/heavy use - is in fact the entire fields and the whole tank completely full of water where water from the house simply can't exit?

titanoman 01-09-2012 03:58 PM

Apparently you don't have enough rock in your leach field.
Did they do a perk test?

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denemante 01-09-2012 04:30 PM

No recent perk test done - I have original paperwork which stated things were good (don't recall actual values).

If this is the case (not enough rock in the leach field) - can I simply deal with it as is? Or is it bad news in any event?

As I said, I saw the tank and the filter - the water chamber of my tank was "clean". The filter had just a tiny bit of growth on it and was "clean". The water level was correct in the tank. The solid chamber was ready to be emptied.

So since this issue has been ongoing - I don't believe I witnessed any damage to the system.

I guess the answer I'm looking for is that I have no worries - just that I'd need to be careful when the ground is soaked and the wife wants to do 5 loads of laundry, etc.

titanoman 01-09-2012 04:48 PM

Other then digging another ditch, pray for sunshine!
I wonder if the original installers put leech paper over the rock.

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jwadd 01-09-2012 04:50 PM

Roots in field lines?

In our area the water table has been rising for several years due to dead pine forests from mountain pine beetle.

Daniel Holzman 01-09-2012 04:54 PM

I don't think you fully understand how your septic system works. First off, the septic tank is always "full", since the level in the tank is controlled by the elevation of the outlet tee. You state that your system "slows down" during heavy rain, which seems to mean that the liquid level in the septic tank rises above the level of the outlet tee, probably because the field cannot accept the flow out of the tank.

This could occur either because the field itself is saturated, because it was not constructed far enough above the high groundwater level (in MA, the bottom of the field is required to be a minimum of 4 feet above groundwater level). It could also be because your septic tank is not watertight, and groundwater is entering your tank during rainfall events (the tank is supposed to be completely watertight).

It could also be because the permeability of the soil in your field decreases as the groundwater level rises, causing a backup through your septic tank into your house.

No matter what the explanation, in no way can this be considered "normal". A septic system is supposed to function correctly under essentially all conditions, except possibly a a massive rainfall event such as 10 inches of rain in a day. It is of course possible that at the time your septic system received a "clean bill of health", the groundwater level was low because it had not rained much recently. Groundwater rises and falls with precipitation, so the time to check a system is when the ground is wet from recent rain, not dry.

My guess is that your septic system was built with inadequate separation between the system and the groundwater level. Based on my experience doing forensic work on failed systems, this is pretty common, especially in rural areas where the systems are often "designed" by poorly trained individuals, or sometimes they are simply built with no design at all.

denemante 01-09-2012 07:34 PM

Thanks Daniel,

Thanks for input. I do understand the basics of the system and that it will always be full (of liquid at least) to the outlet T.

Is it perhaps reasonable to think that my system might be working a bit like a tea press? Let's say the fields get too saturated. They can't purge off water fast enough. The tank then fills from water use. There's no where for sewage to go - so it would start to back up.

But perhaps given the nature of my pipes and their depth in regards to the house - they begin to fill up towards the house - but never to the point of backing up into the basement bathroom. The weight and pressure of that volume in the pipes "pushes" into the overly full septic tank, which in turn "pushes" liquids out into the saturated fields. It's slow - but it goes. As things dry - it works normally again.

Secondly - I should have mentioned something else. I actually don't have a completely clean bill of heatlh. The previous owner installed a patio over the main line out to the tank. That line turns 90 degrees at an elbow into the tank. It appears as if the weight of the patio pushed the main line down - it "bent" at the elbow but didn't break - so there is effectively a low spot at that elbow where waste can sit. The low spot is only perhaps 1/8 to 1/4 of the diameter of the pipe. It's presumed that stuff will accumulate there, but eventually get washed out into the tank. I also have an access wash-out in the patio 10 feet from the tank which points in the direction of the tank - so could manually help this process if needed.

I honestly forgot about this. But I wonder if this single thing could cause my "slowness" on occasion. Not sure why it would seem to happen more in winter (Atlanta, rare ground freeze) and when it rains - then go months and month with no issues at all.


AllanJ 01-09-2012 07:51 PM

Yes it is possible for rain water to overload the leach field particularly if the field is in a "low area" of the land and water tends to accumulate there.

denemante 01-09-2012 08:57 PM

Allan - other than the system "slowing" - is there any particular damage or anything else that might happen if a field gets saturated as you say? Or is it just an annoyance?

AllanJ 01-10-2012 08:56 AM

Ordinarily it would be just an annoyance, the septic tank itself will fill from the normal resting 85% level to to the brim (100% level) and, next, your plumbing will back up.

But some septic tanks have open top baffles, e.g. the sideways T pipe at the outlet may be open at the top as well as at the bottom. Then, if the level rises too high then grease (from the scum layer) will spill into the outlet pipe and make its way to the leach field and commence/accelerate the leach field failure process. The purpose of baffles (or T pipe) is to prevent that from happening.

If you have a low point (belly) in the drain line then it will sooner or later become a bottleneck as solid matter accumulates there. The normal flow of sewage is not fast enough to keep solids moving along. (The same septic action as occurs in the septic tank will decompose and liquify some of the accumulated solids so the line does not become clogged that rapidly.) You may want to have a drain specialist "flush" or "jet" the line periodically until you can dig up and re-lay the line.

denemante 01-10-2012 09:08 AM

Thanks AllenJ - the baffle between my liquid and solid chamber has a horizontal slot across the center - perhaps that's why I can continue to experiance "slowness" or minor stoppages when the tank goes to 100%, yet the liquids chamber still remains clean.

As for the low spot - is jetting like pressure washing the inside of the main drain line towards the tank? I've got a 6 inch cap in my patio. You open it and it curves towards the tank which is 10-15 feet away. That section is where the low spot is. I wonder if I could just stick a running garden hose down there periodically to "rinse" out anything that's sitting in that run.

AllanJ 01-10-2012 02:34 PM

The garden hose full blast may or may not succeed in flushing out a low point in the drain line.

If you are able to get the hose in quite far and push and pull it back and forth through the low point, you may flush out much of the accumulated solid matter. But when you are done and withdraw the hose, it will be disgustingly filthy.

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