Household septic systems guidelines
For a 4 bedroom and 2 bathroom dwelling, typical of many family homes, a commonly used eptic system comprises of 1 x 1520mm septic tank, 1 x 1220mm septic tank and 2 x 9 metre precast concrete leach drains, Drains with a maximum cover of 400mm from the lids to finished ground level, connected via a diverter box.
OR
1 x 3,200 litre baffled modular Polyethylene Septic Tank and 2 x 11m
Polyethylene Leach Drains with a maximum cover of 400mm from the lids to finished ground level, connected via a diverter box.
If you are designing a system for a home you should note that this applies to the following site-specific criteria being met:
1. Ground water table minimum of 2200mm from natural ground level; Leach drains to have a 1:200 fall from the inlet
2. Sandy soils;
3. Site not subject to inundation of flood waters; and
4. Leach drain area is a minimum 30 metres to any bore, well, stream or any underground source of water.
OTHER STANDARD CONDITIONS which should be noted
5. Leach drains to be at least 1.8m from any structure or boundary and septic tanks to be at least 1.2m from any structure or boundary.
6. Leach drains to be 3.6 metres apart from side of drain to the side of the other drain
7. A distance of 1 metre between septic tanks is to be complied with
2 Responses to “Household septic systems guidelines”
Water will not infiltrate through a mortar-less paved walkway as rapidly as grass. Many municipalities in Lake Cook counties of Illinois perform calculations on the aggregate size of all impervious surfaces versus the total property area. Paver patios, walkways and driveways are included in these impervious surface area calculations but are typically deloaded by only 30% maximum. Another way to look at this is that these linear surface structures inhibit 70% of the water that falls in the form of rainfall. Again, in their view, it is the amount of run-off that occurs during a typical rain storm and not what is possible if you run a slow soaker hose over these surfaces. These surfaces do impede significant rainwater amounts at the rate that rainwater typically falls. Hope this is helpful.
What Well Lit Garden said is right, however there are types of pavers made specifically to allow water to permeate. Here is a link to one example.