Drainfield Repair: Help with the Septic Field

Drainfield repair is occasionally necessary. It occurs for many reasons, but the most common reason is overgrowth of the biomat.

How It Works
The tank’s purpose is to capture all waste from the house and to provide a place for organic material to settle out of the water. Some of the material, like grease, oils, and fat, float to the surface forming the scum layer, while heavier material settles to the bottom of the tank forming the sludge layer. Once material has separated, the remaining liquid is called effluent. The field’s purpose is to absorb and purify the effluent.

Amazingly, the effluent is purified by bacteria that live in the drainfield. As effluent travels into the field, a colony of anaerobic bacteria called the biomat grow naturally and feed on all the contaminates in the effluent. In order to hold themselves together, they forms a black, sticky substance that allows water to pass very slowly; this substance causes the effluent to gather giving the bacteria enough time to digest all the harmful particles. It’s the perfect natural filtration system, but as a natural system, it can easily get out of whack.

Drainfield Repair Cause

Drainfield Biomat

Importance of Pumping
Regularly pumping the septic tank is so important to prevent drainfield repair because the sludge layer will build up over time decreasing the space inside the tank. As space inside the tank decreases, material has less time to settle leading to effluent with suspended particles of organic material reaching the field.

Not only can this material clog the distribution lines but provides excess food for the biomat. Too much organic material will cause it to grow uncontrollably becoming so thick that water is completely trapped. Once it reaches this point, it has clogged the soil and can be very hard to fix.

The standard procedure for drainfield repair is to install a new one; however, that can be very expensive for the following reasons:

  • Local Government: In the vast majority of areas across the country, local government is heavily involved and concerned with repair and septic system installation. Usually, you’ll need a perc (percolation) test from a soil scientist and a plan showing the system will have enough capacity (based on number of bedrooms in the house) in order to get a permit. Frequently, they will have more strict rules than they did in the past and will require a larger drainfield than the original.
  • Perc Sites: In order to receive a permit from local government, a soil scientist will need to find a suitable “perc site” on the property. In general, they’re looking for an area that will absorb effluent without allowing runoff into fresh water supplies. The most familiar test is the soil absorption test where they’ll watch and measuring the length of time the ground takes to absorb a certain amount of water….In addition to the absorption test, the soil scientist also does research with topography and other geological maps, looking at slope, bedrock depth, groundwater elevation, and soil type. After all of this, a property in question may have multiple perc sites or none at all. If the site doesn’t have another perc site, then you may have to dig up the whole field or do some sort of expensive work-around.

One Possibility
Allowing a drainfield to “rest” for 6 to 12 months will usually cause the biomat to decrease and restore the soil’s absorption ability; of course, you can’t go without a septic system. If your property has enough space, it might be possible to install extra distribution lines next to the existing field with a valve that will allow you to send effluent to the new distribution lines for six months. Then, you can restore flow the the old “rested” lines. If it works, you’ll always have a set of backup distribution lines. The only way to know if this repair idea will work is to ask a contractor because each property is different.

More Ideas
There are multiple less expensive ways to restore a drainfield that you should try before installing a brand new one. They’re discussed in this post: septic drainfield restoration.



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