My county's application for a septic tank permit asks if I want to use "alternative absorption field products" instead of pipe and gravel. They won't make any recommendation of one type of absorption field over the other. It could be that they are using a weird phrasing, or I'm not using the right search terms, but I'm not finding any information on what an "alternative absorption field product" is, or why I would want one instead of traditional pipe and gravel. Can someone please explain what they mean, and why someone would or would not want this?


There are several different types of leach fields, the most common is the gravel and pipe you know about. There are others that use chambers made out of plastic and sometimes just dirt. I have only installed 1 chamber system and the cost of the plastic sections was higher than the traditional gravel and pipe but the owner wanted to try this method because they used a garbage disposal (not good for leach fields because the fines plug the system) . there are also sand filters used with pumped systems and large mounds or very large grids with nozzles that drip the liquid when under pressure these systems are needed when the property fails perc testing (not enough drainage due to soil conditions usually high clay) these are the most expensive systems to install and require the highest maintenance. The standard is method is all that is required in many cases. But chambered systems may outlast a conventional system the chambered system we installed has only been in for. About 10-12 years and they have had no problems with it that I know of. If you want to find more information or types use the term leach field.

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  • IIRC "Basins" is another common term for the chamber referred to. Sometimes they are concrete. – Ecnerwal Oct 30 '17 at 14:26
  • Are any of these systems proven? In cases where a special system isn't required by site conditions, are there any advantages? – Nick Oct 30 '17 at 15:48
  • Basins are more effective than pipe and less prone to clog. They typically cost more. – Ecnerwal Oct 30 '17 at 16:41
  • The advantage of the chamber system was it did not plug up with fines, the disavantage was you could not drive over them and they cost a bit more but not much. I don't remember the weight limit on the type we put in but it was less than our back hoe, not much diferent than a full sized truck with a load. This was the only negative I remember. As far as proven I don't know how long chambered systems have been on the market but have seen standard leach fields 50-60 years old that were good enough for a new tank when we replaced the redwood tanks. – Ed Beal Oct 30 '17 at 17:40
  • "basin" is another term for the "chamber" (and there are, IIRC, concrete as well as plastic versions.) – Ecnerwal May 14 '19 at 12:10

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