We have started laying the in-ground pipework – stormwater, ring main, and mains pressure feed.
Originally I was going to lay the sewer pipe in the same trench as the others, but have decided that I cant achieve the correct fall on the sewer if I use these trenches. I need at least a 1:100 fall. So I will have to redig a separate trench for the sewer. This is a bit of a pain because I ether need to re-hire the dingo trencher (at $450 per day), or use my backhoe which will be much slower and dig a wider trench. I’ll probably end up using the backhoe to save some money.
So down the south trench I put in the 32mm blue line pipe for the mains pressure line that will be used to fill the tanks if they ever run dry. Then on top of that we lay the 90mm storm water, with takeoff for the down pipes. Then on top of that goes the 50mm blueline for the ring-main, with takeoffs for the house/workshop water supply, garden taps, fire hose points, and fire sprinkler points.
Refer to this post for tips on getting the trenches set up right. Because of some of the failings mentioned in that post, we had to work a bit harder on the stormwater line.
The stormwater pipe is back filled with ‘1/4 minus’ screenings so it is properly supported all round. The screenings easily flow under the pipe and into all the dips and hollows, especially with a bit of tapping and tramping with a stake.
Because we are using charged storm water lines (where the water sits in the lines permanently) we didnt have to worry about the fall of the pipes. The reason for this is that the water tanks are sitting roughly at the same ground level as the house. So, the inlet to the watertanks is about 2.1 meters above ground level. The guttering on the house is about 3 meters above the ground, so there is a ‘head’ of about 0.9 meters between the water coming off the roof (guttering), and the flow into the tanks. But that means there is water in all the stormwater drain pipes from the height of the tank inlet to the lowest pipe. Thats all ok. However you really need to ensure there is a way to purge this water, as you dont want it to go stagnant. So if the weather has been dry for a few weeks, then just before a rain, dump the water in the pipes.
You can see in this picture (above) the dump gate (its not fully plumbed up yet).
Important note: I didnt bother to read the install instructions for blueline pipe, so I just backfilled the pipe with the dirt from the hole. This is OK if the dirt does not contain any rocks greater then 15mm. However, ours does – sandstone chunks. So, now I need to dig up what I have filled in (about 30 meters) and put in small screenings to protect the pipe from abrasion by the rocks. What a bugger !
50mm blueline pipe is heavy. It helps to have a tractor 
We have also made up two steel riser posts to support the stormwater outlets for each tank.
These posts bot onto the concrete slabs that the tanks sit on. Eventually I will paint the pipework and posts.
