[permaculture-oceania] Grey water reticulation

[jedd]

On Friday 09 June 2006 10:32 pm, Dick Copeman wrote:
 ] I am seeking advice about reticulating grey water to young fruit trees in a
 ] backyard garden.

 Hi Dick,

 Well, there's some challenges involved in there, to be sure.

 I think you're always going to need a filtering system, but given the
 low flow rates, you can probably get by with something a bit more
 passive than those 'clean three times a week' jobs.  I've seen one
 for a 2" poly pipe system that is basically an angled metal mesh,
 at about 45 degrees to the flow, and diverts down a (tappable) pipe.

 If you've got a relatively low volume of grey water, maybe a dual-
 staging tank system, alternating tanks to allow a 24 hour settling
 period, with some kind of drainage plug / sump system .. ?

 I'd be dubious about the options you've discovered so far:

 o 13mm purple sullage hose with non-blocking drip holes,
     but only one hole every 300mm.
 
 Not just because it's $2+ / metre, but those holes are way too far
 apart, and it sounds like (!) the holes aren't opposing (which is
 the common way of stopping holes blocking up with non-filtered
 water).

 o  50mm slotted ag-pipe, which seems to be too large a diameter for
    watering a young fruit tree.

 Agreed, particularly for low flow rates.  My bigger concern with this,
 beyond the $2/m cost of 2" poly, would be roots forcing their way
 into the pipe, ultimately rendering it useless.

 ] One irrigation supply fellow suggested I use 19 mm poly pipe
 ] and drill or cut my own holes or slots in it. There is also a 25mm
 ] unslotted ag pipe, which I could drill or cut holes or slots into.

 Insanely tedious activity -- avoid if you can.  Holes also invite
 roots, and roots lead to the dark side, etc etc.

 The requirement to have the pipe below ground is a bit limiting,
 and pretty much rules out dripper / hole style devices.

 Two options spring to mind.  If you've got a small area that you're
 happy to divert this greywater to, consider a rubble drain (excuse
 me if this is sucking eggs time, but for the listeners at home -- dig
 a ~60cm deep trench, 20cm wide, a few metres long, drop in 10cm of
 small pebbles, pop on an inverted U-shape black slotted poly drain,
 backfill with pebbles, then soil).  They take eons to silt up, by
 which time plants are nicely established.  Might not work if you've
 got an awful lot of greywater feeding into the system.

 Other alternative is the Leeaky <sic> Hose approach -- not sure if
 that comes under one of the categories you listed.  It differs from
 most drippers/weepers insofar as it's not made from normal pipe
 with lots of holes punched in it .. but rather, discourages root
 penetration by being a kind of 'foam' design.   Two problems
 exist with this -- you need a bit of head to feed it (I think they
 suggest 8psi <scuse imperial> to give you 4l / metre / hour, but do
 please check the figures on their web site.  So you may prefer a
 header tank in order to give you sufficient pressure to drive it.

 You'd also need to flush it fairly frequently, but if you design the
 system sensibly up-front, it's pretty easy to facilitate this.

 I've been using this stuff on some lengthy and low-pressure runs
 (2 metre head, 40 metre runs) and it works fairly effectively.  My
 biggest problems with it so far have been that it really hates being
 exposed to intense sunlight (it seems to seize up), and the wildly
 varying pressure I get between a full water tank and a near-empty
 one (1 metre to 3 metre head).   Oh, and you also need to make all
 the runs as close to horizontal as possible -- that's a design issue.

 There's also a potential problem with nasties leaking out of it
 (see earlier discussions on this list wrt heavy metals coming out
 of buried car tyres).  Given it's made from recycled car tyres ...

 On the upside, it's designed to work with extremely low pressure
 systems, it's flushable, it works best when run under the soil, you
 don't get blockages at single points, and it's about $1/metre.  Note
 that the last time I checked, Big W sold it cheaper (per metre) in
 15m lengths than the manufacturer was able to sell it to you directly
 at 200 metre lengths.  Go figure (but don't tell too many people).

 Jedd.