Sunday, April 3, 2011

Drainage with Nerd Cred

This last week has been all about drainage. I didn't catch any photos of the little trenching machine, but it was about the size of a ride-on mower. Here is some of the work it did:

Drainage pipes aren't terribly exciting, of course, though important. Most of them look like these -- PVC pipes, which are here connecting to the sewerage line from our future toilet.

I asked for polyethylene pipe to be used instead of PVC where possible. PVC, though it is ubiquitous, creates dioxin during the manufacturing process and requires the use of poisonous "blue glue" at the joins. It is also hard to recycle, as it is a thermosetting plastic, and releases chlorine when burnt. However, I was surprised to learn that as they are brittle, PVC pipes are usually only guaranteed for 10 years. We have mobile clay soil, so even at a practical level PVC isn't suitable for stormwater here. Polyethylene is considerably more flexible (Vinidex assert that PE pipes were the only ones to survive the Kobe earthquake! I suppose clay soil will be all right, then) and even better, can be recycled.

What I hadn't realised was how you join PE pipe. See the O-rings in the picture below? And the two protrusions on each one?

These pipes are electrowelded! On Monday, a little electrofusion machine is arriving from Melbourne* to put a current through wires in each ring. The inside surface of the O-ring melts, fusing the join, and a yellow tab pops up to indicate the weld has been successful. After the job is complete, the machine will print a list of the welds performed and whether it thinks each was successful (the rings are barcoded). We feel that the amount of technology used to nuke solve a simple problem gives this method real Nerd Cred. (And while using HDPE pipe doesn't cost much more than PVC, the O-ring electrofusion couplers are expensive.)

Of course we also found a minor problem this week. Our gas line is too close to the surface to meet the current code, and it's got at least one bend in it, like this one. This section of the pipe was attached to the concrete driveway -- another no-no these days -- and broke when the concrete came up. Our builders suspect that there is more gas-pipe snaking around in peculiar places, and they are planning to hand-dig the driveway so they don't hit it.

* Melbourne seems to be way ahead of Sydney in the green building area, which is TOTALLY absurd. Where are the green builders in Sydney?

1 comment:

Anonymous said...

That does have nerd cred indeed! who'd have thought that laying pipes would be so technological based?