Septic Tank Failure
Failing systems that result in water coming to the surface are a public health hazard and can cause surface water contamination by nutrients and pathogens. If a system is functioning hydraulically (i.e. accepting the water) in a slowly permeable soil there will be very little environmental impact.
In the course of doing service work we are seeing a disturbing trend. The systems we are seeing are systems that, for the most part, meet the minimum requirements of the State and local rules, but are experiencing what we consider to be premature failures or too frequent repair requirements. In the interest of improving satisfaction with and the performance of systems for the homeowners, we are offering the following discussion.
What we are seeing is an increasing number of drip systems with clogged tubing. In some cases a history of high water alarms due to clogged filters, or excessive hydraulic or organic loading of the treatment system precedes this clogging of the tubing. In other cases, there is little to no prior problems, just a rapid decline in flow that is accepted by the drip tubing.
For the record, we do not see a correlation to the brand of tubing, the brand of ATU, the designer, or the installer. What we see is a correlation to the lack of control in the hydraulic loading of the tubing, the flushing of the tubing, the frequency of this flushing, and inadequate effluent filtration.
In contrast, we have been servicing some very resilient drip systems that have been in the ground, in some cases, for over 15 years with virtually no reduction in the drip tube flow acceptance. The interesting point to consider is that these very resilient drip systems are handling septic effluent, not secondary treated effluent. Clearly, it is not the quality of the effluent that is the challenge to the long term performance of subsurface drip systems.
These systems have in common the following: First, they utilize timed dosing of the effluent to the tubing. Second, they employ frequent aggressive flushing of the drip tubing. Third, they do not merely rely on a single pass through a screen or mesh filter. They employ some form of three-dimensional filtration.
What we conclude is that for a subsurface drip dispersal system to function successfully for decades, it must have timed dosing to limit the hydraulic loading, proper field flushing of the tubing, and proper effluent filtration. The quality of the effluent the drip system is handling does not appear to be nearly as important to the life of the subsurface drip dispersal system as hydraulic loading, flushing, and filtration.
While we cannot dictate to designers and agencies what they should design and permit, we do strongly recommend that all subsurface drip dispersal systems be designed and installed with timed dosing, aggressive and frequent field flushing, and with some form of three-dimensional filtration for the effluent.
Snowden On-Site, Inc. would be pleased to assist you with equipment, even for retrofits, that provide all the above-described functions.
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