Septic System Instalation

[tatom]

I would like to know how to install a plastic septic tank. I havent found anything on the net for instaling the ones that are shaped like a hand grenade. I saw a diagram of one that showed it sitting on a concrete pad and it said to fill with water before backfilling, but thats all.

I will probably buy a small one as it will only be for one toilet used by 1 person.

Ive been reading about leachfields here on the forum. Some guys have built western style fields but I havent heard how the have held up over time. Instead of a leachfield, I think I will build a drywell for the overflow from the tank. This is just a big hole in the ground, about 2x2x2 meters filled with large stones, broaken blocks, bricks, etc, anything to create voids. I have built several septic systems in the west and I prefer the drywell to a field. Everyone Ive built is still working today, some after 50 years!

Any help will be appreciated.

[Crossy]

Ours just sit on concrete pads and backfilled. We run the effluent direct into the local (large) river just like all the other properties.

Watch your water table if you go for a dry well, it may end up wet

[sirineou]

A concrete pad to support the weight and prevent settling of the septic tank and and breaking of the input and output pipes. Remember water weights a lot

(8.3 lbs/gal).

Fill it with water as soon as possible to prevent it from floating up if the hole it is buried in is flooded (I have seen them pop up like a cork breaking all the connecting pipes)

if you have the property space, a leach field with the proper angle away from septic tank is best for a couple of reasons,

one it is close enough to the surface not to worry about ground water, the angle away from the septic tank takes care of the surface water

Two, if located in a sunny area, evaporation will aid in getting rid of overflow. (and as a bonus your grass will grow best there)

In the absence of sufficient space for a leach field , a dry well works good, only a couple of problems,

one is you don't have the evaporation to aid in getting rid of the overflow,

two you have a limited area for the overflow to permeate the ground, this can be a problem in areas with a slow perk rate,

and three because it is deeper you have to worry of ground water, as it was mentioned by Crossy.

For a dry well a few concrete rings in a hole with an open bottom, and with a little gravel in the bottom works well, (which is what most people use here in LOS)

[tatom]

Thanks for the tips.

Now, how big should the leachfield be?

Ive read that here we have to make our own perforated pipe. (no problem)

Do you make a distribution box, or just use pvc "T"s?

I have plenty of land, no flooding, and the ground absorbs water well.

The toilets I have now just go into a Thai style tank, (concrete rings) and it works quite well. I have lots of time and like to keep busy,

so I thought it would be fun to build a western system. Life here is great. Right now Im remodling the temple kitchen and building a treehouse for my wife. I just want some jobs lined up so there is no down time.

Thanks again,

Tom

Khon Kaen

[canopy]

A "drywell" has several other disadvantages. With a drain field, 40% of treatment happens after the septic tank. With a drywell you get none. A drywell leaches waste in a concentrated area which contaminates ground water. Basically, a drywell is not a good system and does not meet minimum international standards.

To size your drainfield you need to know your soil percolation rate. Something like this: http://www.inspectapedia.com/septic/fieldsize.htm

If you are perforating pipes yourself then make sure to read up on how to do this properly. There are good rules to follow like only placing holes at 5 & 7 o'clock. You can also buy pre-slotted PVC pipe in various thicknesses. The 4" pipe in 8mm thickness seems quite durable.