LPED, drought proof your garden

Fri, 11/09/2012 - 18:57 — Compost Stu

The Currawongs are having a council in the nearby Silky Oak. It must be a serious issue because the politics are raucous. They dive and chase each other, perhaps delivering their own form of justice, or are they just finding out who has the biggest beak….? The dry spring weather is wilting the weeds and keeping the lawn nicely stunted, drying up my leaky dams and reminding me of the last drought. My vegetable patch, however, is flourishing. Treated grey water irrigates about 200m2 of beautiful red soil, simply by having a shower or doing a load of washing. The grey water is treated using a grease trap, (emptied to provide material for the compost heap), a sullage tank, which allows any sediment to settle and any remaining greases / fats to float, and then a reed bed. The reed bed filters the grey water through 10mm blue metal and produces an effluent that is clear enough to see through. It still has some particulate matter in it but this is just food for the garden, as it provides a substrate for Phosphorus and Nitrogen to attach to.
The next part of the system is a little more intricate. A dosing siphon (or bell siphon) is built into a large outlet tank (a 450L pump well is ideal). A dosing siphon is a passive device that works on water displacement to open a pathway for a large volume of effluent to leave the chamber at one time. This eliminates the trickle flow that is typically released from treatment systems. The dose, (up to 150L) flows down the hill to the garden where it is distributed by a low pressure effluent dosing system (LPED) over the required area.
The LPED system is constructed from PVC pressure pipe (UV treated). It must be designed to distribute the effluent evenly throughout the garden, this can be the tricky bit as when working with gravity, there is no constant head over fall. It can be done carefully and patiently with a various small drill bits and a tube of silicon. Using spacings of 600mm, drill small holes (2mm) in the PVC pipe facing up, and begin to test the flow rates through different parts of the system. The differences in flow rates can be adjusted by drilling larger holes where required. Once this is established, cap the holes with pieces of 100mm PVC cut length ways. The PVC irrigation lines should be able to be isolated and removable, so you can turn off the water to that bed and remove the line to re-work the bed, so don’t glue them in and use plenty of valves. The lines should be covered in mulch to comply with council guidelines, and this will help prevent excessive evaporation too.
Pooh Solutions specialises in the design and implementation of LPED systems so please speak to us if you need further advice on how to drought proof your vege garden this summer.


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