Septic Soakage Trench

Hello
Does anyone have any knowledge of dimensions of a soakage trench for a small septic tank?
This tank will have WC running into it only (2 occupants,no other waste) I have looked at specs from Council/Health Dept etc. My first guess is:
16m long, 1.5m-2m wide & 1m deep.
Filled with 20mm/40mm mix of aggregate and using 100mm perforated pipe.
The existing trench is past its use by date and I don't want to dig it up to check dimensions
Many Thanks Paul

PS. In June advice from the Forum helped me talk SWMBO out of lining the bathroom in pine. Thank you - I wasn't looking forward to doing the job.

Check with your local council or better yet a plumber they will be able to give you the good oil.I have the same problem and the plumber informs me that if I officially notify the council that I am going to install a new trench that they will make me put in a bigger system ( tank )as the specs have changed from days of old and my system is now regarded as inadequate for the size of house:eek:

Paul,
trench dimensions will vary depending on maximum possible discharge (if there's just 2 of you but the house has 5 bedrooms and 2 bathrooms council will reqire greater capacity than if there was 2 of you in a 1 bedroom house. Soil absorbtion rates will also impact on trench dimensions.

Mick

I got sprung by the local health inspector a few days before we were going to replace the old septic drains. It resulted in having to put in a lot more drainage than previously.
Sometimes it doesnt pay to try and beat the system.

The length of the trench should be OK and the depth but usually you put a half round plastic stuff (can't remember what it is called available from Bunnings) with stiffening ribs in it. They are about 1500mm long x 600 to 700 wide and you lap one over the other by one rib and put this in the bottom of the trench hollow side down. Cut a hole in the side of it and run your sewerage pipe into it at one end.

Fill the trench to within about 6 inches of the top of the trench with about 2 inch aggregate, put tar paper over the aggregate and cover it with dirt. The tar paper is to stop the dirt falling down into the aggregate.

I know this because this is how the plumber told me what to do.

Where abouts in Sydney are you that you wouldn't have sewerage. If you go to the council they will probably make you put a Bio-cycle system in.