A published column invariably leads to either additional questions related to the topic or comments that are especially pertinent to the discussion. For example, a reader sent in a question about roots getting into their chamber system and plugging and clogging all lines. They wondered if taking out the offending tree would solve their problem.

The answer is clogging will be a continual problem until the reason for root penetration into the system is identified and solved. Taking out the water-loving tree — in Minnesota this is most often a willow, white pine or spruce; in southern states palm trees is certainly part of the solution — but a watertight system is also a root-tight system.

Typically, roots will not directly penetrate into trench media whether rock, chambers or other acceptable media. When a trench is standing empty, it should be dry and since roots are in search of water and nutrients, they will not enter into void space because there is nothing there. 

WATER ATTRACTS ROOTS

Periodic water indicates another problem with the system, such as being too close or into the seasonal water table where the trench is acting as a drain. If effluent is ponded in the trench, sewage is anaerobic (without oxygen) and the roots will congregate around the outside of the trench where they can obtain water and nutrients in the presence of oxygen once the biomat is established. 

There are several other reasons and locations that can lead to roots clogging parts of the system. Locations where piping enters or leaves tanks, distribution boxes or sewage tanks should be checked. Running a camera through a cleanout or from the inlet or outlet of a tank can identify if piping is watertight or if there are breaks or areas where roots are penetrating.

A poor glue job at pipe joints can also lead to problems. Several years ago I was working on a mound demonstration and the installer indicated the pipes in the distribution system had been glued and it was ready to accept water. Fortunately, we turned the pump on to see what kind of distribution we had before we covered everything up only to see water coming out of each pipe joint instead of the perforations! 

This was due to the lack of understanding by the technician that pipe gluing with the adhesive they used was a two-step process. Each joint separated when water was run through the system. This can easily happen and something that is taken for granted because everyone knows how to glue pipe. It is the reason pipe gluing is still a topic in basic training workshops I teach.

Other activities can cause piping to not be watertight. During backfill of the system pipes can become damaged and cracked resulting in small leaks and providing locations where roots can enter the piping. Often this cracking can occur near tanks or distribution boxes where piping into or out of the device is not properly bedded and supported. This can occur after installation due to differential settling around the tank.

EDUCATE HOMEOWNERS

Pipes can also be broken or cracked due to homeowner activities after installation. Sewage treatment systems should be protected from vehicle traffic. Heavy equipment, trucks or tractors passing over the area could damage shallow pipes, even when properly bedded. It is important to talk with the homeowner about proper care and management of their system to avoid these issues.

Other common locations for systems to not be water or root tight are at pipe penetrations into sewage tanks, distribution boxes or other tanks or boxes for additional pretreatment such as peat, sand or media filters. 

In sewage tanks, obvious problem locations are the inlet and outlet, the top seam around the cover of tank and any middle seams. Inlet and outlet penetrations must be properly sealed. Some rigid or plastic seals and any seal formed with mortar or mastic may be stressed during backfill and will likely leak and allow root penetration. Any attempt at bonding wet mortar to dry concrete or PVC pipe is bound to fail, allowing root penetration. In the past bituminous seal, mastic or concrete grout have been used with varying degrees of success.

The best way to provide watertightness is to use flexible gaskets cast in place at the time of tank manufacture. Rubber seals are most desirable because they are flexible and will stay sealed during backfilling and settling. If cast at time of manufacture, these gaskets and boots must be protected during installation so they are not damaged and become ineffective.

SEAMS LIKE A PROBLEM

Seams are typically at the top of the tank or in the middle if a tank is constructed in two pieces. A butyl rubber or asphalt-based sealant is applied to the seam before connection. In center-seamed tanks, a tongue and groove connection along with a sealant and then after connection use of a butyl rubber wrap around the outside of the tank ensures watertightness.

Similarly, seams at the top of distribution or drop boxes, as well as pipe penetration locations, must be properly sealed. Drop and distribution boxes typically have the pipe penetration gaskets installed at time of manufacture. Care must be taken during installation to cut these gaskets, so they provide a tight, flexible fit. Using similar rubber or asphalt mastics for seam connections (usually at the top) may be necessary and are effective.

Remember a watertight system is a root-tight system!