Septic Systems in Thailand

As with the variety of building materials, building styles, and various shapes, the septic systems found in Thailand have variety. Some are set up along lines found in Australia and other developed countries, while other systems are much more rudimentary. Poorly designed or situated septic systems are obnoxious and can be hazardous.

Septic tank/systems

There are essentially two kinds of septic tanks in general, as used in Thailand: the simpler and cheaper poured concrete boxes, and the engineered plastic systems. For engineered, a typical make and model, for example, is the DOS ST-20/BK-1000L.

Secondary Outflow

Coming from the septic take is the outflow. One typically finds three ring concrete forms with no bottom or gravel bottoms. Sometimes there are multiples of the ring system, depending on if different inputs (graywater, blackwater) are integrated. These rings hold and disperse the outflow liquid into the surrounding land.

Tertiary Outflow / French Drain / Drainfield

Much less common, but not difficult, is a french drain/drainfield that can be used to further disperse the liquid over more land area. Geotextile can be used to keep materials separated (the surrounding sand/clay/soil and the rocks surrounding drainfield pipes).

Pumping out septic systems

It is possible to have a well-functioning septic system which does not need to be pumped out. Part of this has to do with operating capacity as well as ensuring the microbial environment is conducive to ongoing functioning, including:

  • Not putting graywater into the system;
  • having proper flow between blackwater sources, septic, and dispersal;
  • not using harmful chemicals for cleaning; and
  • if needed, adding additional microbial food/sources to ensure full operation.

In Thailand there is much less use of graywater into a septic, mostly to reduce the required capacity of a septic system (thereby making the septic cost less).

Integrated Septic and Graywater

There are naturally three sources of gray/blackwater:

  • Toilets (blackwater),
  • Bathroom sinks and showers (graywater),
  • Kitchen sinks (graywater but with greasetraps needed), and
  • Laundry (high volume graywater)

All of these can be combined into a septic system, but that is much less efficient, as each of these water sources have their own characteristics and requirements, and potential for reuse.

  • Blackwater to the septic,
  • Bathroom graywater to the toilet flushing,
  • Kitchen sink graywater to a grease-trap (if needed), and then to dispersal,
  • Laundry graywater to fruit trees, non-edible plants

P-traps for Kitchens, Bathrooms

In Thailand, P-traps are much less common. The key for the p-trap is that helps trap debris as well as having a water stopper so that unpleasant odors do not come back up into sinks and toilets.


To simplify drastically, there are two kinds of composting (three, counting the bury in the yard approach, which is the common Thai variety).

What kind of composting depends on what needs to be composted. In both cases, the actual organisms at work are microbes (and not worms, in the case of worm composting).

Worm Composting

Worms eat microbes, not rotting food. Rotting food is eaten by microbes, hence the food source for the worms. Works of course help break up the food source of the microbes. This is akin to how humans (and most animals) digest food: they don't, but microbes and bacteria help do this for us.

The issue with worms and the standard aerobic microbes found in worm composts are that citric, oils, dairy, and meats are antithetical, and also attract various other kinds of creatures (roaches, rats, etc.), not to mention create bad smells. These materials need to be dealt with by way of hot composting.

Hot Composting

Just as with worm composting, it is microbes that make hot compost. Heat should not get above 65c or higher, or the microbes will become damaged.