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Question DetailsAsked on 9/21/2016

What can I do if my septic tank fingers are not working?

What is causing my septic holding tank to fill rapidly?

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2 Answers


First off - be sure the tank is actually filling rapidly - not that you have a blockage in the lines to the tank (assuming you are having backup into the house).

You say rapid tank filling - I presume you mean it is overflowing, because the tank itself fills to the outlet pipe as fast as water comes into it from the house - so for the first day or two after pumping out it is filling, then holds at that level with the solids and floatables being trapped in the tank, and the effluent (the "black water") flowing off into the leach field to drain away into the soil. Tank level will stay constant (within a foot or less depending on heavy rains or snow meltwater) from that point on until the leach field refuses to take the incoming flow due to porr soil permeability,, excessively high groundwater, or drain pipe blockages. You get it pumped every couple to 10 years (depending on household usage characteristics and number of residents) to keep the solids and grease from moving into the leach field where they can block it off - but the water level in the tank stays quite constant at the outflow pipe level (tuypically abotu 80-90% tank full) once it has initially filled up after being pumped out.

If no backup into the house, then cause of septic tank overfilling could be:

1) high groundwater in the leach field due to rainfall or local flooding,

2) groundwater or leachfield water filling the tank through a cracked pipe or tank (usually only if tank is lower than the leach field and uses lift pump because otherwise leach field water level = tank water level and is at or hopefully above groundwater level),

3) failed or plugged up or depowered lift pump (if you have a lift pump from tank to leach field because your topography or proximity to other fields or wells or houses mamdated building it higher than the tank and house outlet pipe),

4) blocked or collapsed septic tank outlet pipe preventing or limiting outflow,

5) sludged up leach field manifold or distribution box where the decanted liquid from the septic tank outlet pipe goes into the typically 4-8 perforated pipes that make up the leach field distribution pipe 'fingers",

6) leach field distribution pipes are clogged with paper fiber / grease / roots,

7) the leach field itself (the soil) is plugged,

8) the incoming flow exceeds the outflow capacity of the leach field because you have added residents in the house - or sometimes because kids grow to teenagers, who tend to use a LOT more water for showers.

9) rarely, excessive foaming in tank and leach pipes (which restricts outflow) due to excessive laundry soap use

10) rarely, use of toilet paper that does not break down in the tank, but instead makes it through as a fiber mat into the leach field and blocks off the exfiltration holes

11) not real rare - but would have been an ongoing problem at the house rather than a new issue unless ground movement is raising or tilting your leach field or tank (highly unlikely) - is the distribution pipes may have been laid too high, so the water is not actually able to get to the full field extent to seep into the ground. Would NOT normally (barring ground motion) just start to cause issues but could be an issue if this is a house you just moved into or a new leach field - and also could lead to premature blockage of the pipes and field if the pipes are not perfectly level because only part of the field would be acting properly - or if pipes were installed out of level could be causing blockage due to high or low points along the lines. Sometimes can be overcome without digging up the field but generally involves going to a seage lift pump to slightly pressurize the field - which can cause maintenance issues due to the pump - or digging up and raising the tank to an appropriate height.

To diagnose your problem you would need to get the tank pumped out by a Septic company (one experienced in repairs and installation, not just pumping) and each of these components checked - commonly they would first check that any sewage lift pump is working right, then will pump the tank dry and check that inflow from the house is entering it freely, then check that when there is no water coming from the house the tank is not filling from the leach field backflowing (which it will do for a short time while pumping but should stop in a few minutes) or from leakage from groundwater getting into the tank through crack or fittings or access hatches. If that does not find the problem source, they would usually then come back (after dumping the pumped-out fluid) with a load of water and fill the septic tank and measure the outflow that the leach field will handle (using a meter on the truck to measure water flow to maintain maximum outflow), then overfill the tank (to the top) and measure the outflow rate into the leach field under that slight pressure, and also how long it takes to stop backflowing and to drain down to outlet level with no water flowing in. If it does not flow out adequately, then they will either immediately clear out the outlet pipe (if readily accessible) or block off the tank inlet to the manifold or distribution box and fill that and see if the water flows into the "fingers" OK. If so, then pipe from tank needs work. (Sometimes if they do not see inflow to the tank from high groundwater, they will first snake out the outlet pipe and into the manifold as far as possible upon first pumping out the tank - working from down in the empty tank).

If the above do not solve the problem and the leach field is not taking the efflluent water at an adequate rate, then you have two choices - spend bare minimum probably $500 (in low labor cost area and with accessible cleanouts to distribution pipes) and in typical labor cost areas a thousand to three $, for a thorough jetting of the manifold and distribution lines and the openings from them into the soil (the pipes are perforated along their length to let the effluent percolate into the soil) hoping that will restore flow for at least for a few years, or bite the bullet and replace the leach field - dig up and replace the soil and put in whole new pipes if space limited, or preferably in most cases if able to build a new leach field nearby and just abandon the old one in place (if allowed in your area).

A new field is commonly in the at least $2-4,000 range and can be up to $5-7,000 range in some cases - and up to $10-30,000 if your soil does not pass an infiltration test or you do not have the space and clearance from buildings, water lines, wells, and other septic systems for a new leach field so you have to go with a total excavation and replacement in the existing location with new filter material (typically in the $5-10,000 range) or go with a raised bed (largely above-ground mound system) or advanced treatment system - commonly $10-30,000 range.

Commonly people try jetting the leach field at least once before going with the new field approach unless they are in good leach field country and have ample room for a new field off the same tank - in which case if slow infiltration of the leach field is the problem I recommend just putting in the new field right off the bat, because a jetted field is a good portion of the new field cost and is likely to have a limited life (commonly 2 to maybe 5-10 years in the best case) because the soil between the distribution pipes is still going to be plugged with grease and paper fibers and roots so it is a stopgap measure. The cleaning basically only cleans the pipes and jets out a bit of soil at the perforations where the effluent flows into the soil - it does not rehab the entire field. Also - jetting your field can be a bad idea if it happens to underlie your driveway or above-ground pool or tennis court or such because you will commonly get limited settlement in the first year or few afterwards from the jetted-out soil voids.

For professional evaluation of the problem, a Civil Engineer (not an AL Search the List category) who does septic system evaluation and design would be your initial vendor - though a Septic or possibly Excavation contractor would be the one to do the actual work, with design and inspection and certification of the new work by the engineer if a new or rebuilt field is the solution chosen.

Answered 3 years ago by LCD


Couple of follow-on thoughts:

If you have a removeable grease baffle in the tank that might have gotten displaced or clogged - septic tank guy should check that when tank is emptied.

Also - if you have a grease trap downflow of the tank, it getting filled up could limit the outflow to the leach field.

Here is a link to another previous similar question on building a new leach field which might be of interest too -

Answered 3 years ago by LCD

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