Home Forums General Discussion Grey and black water systems

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    Panapa Ehau

    Kia ora all

    I hope everyone’s corner of the world is treating you well.

    I have the delight of my mother moving to live with my partner and kids this coming summer. We are going to build either a granny flat or add a 60m2 extension to our current house. Either way we will be adding an additional toilet and shower. What sysytems could people suggest that are well priced and that work well. At our HPA training in May there was a system that was discussed in Heidi’s place perhaps that had three compartments used gardens for treatment and that was done at a very minimal cost.

    All suggestions are much appreciated

    Nik Gregg

    Humm, I’d be interested in others wisdom on this one also….


    Hi Panapa
    Suggest you look at Simple Waste Water Solutions – refer http://www.swwsnz.co.nz/index.htm
    They are worm based systems. Friends have installed one of the stand alone systems on Waiheke and it works well. No smell and the worms handle intermittent use.

    Scott Willis

    Hi Panapa,
    Local councils can make this simple or a challenge. In our neck of the woods, there are many different systems, some fully permitted, others not, and some original. Good and bad systems exist in both permitted and ‘independent’ systems. Good to ask about systems at your council – they may know of sensible solutions (particularly if an EcoDesign Advisor works there ; )

    The most expensive system is probably a septic tank that mixes both grey and black water – beware of any that require oxygenation 24/7 as the ongoing costs are equally good at making dollars disappear as much as waste water.

    Eliminating black water from your waste stream by using a composting system POTENTIALLY makes a cost effective and sustainable system possible. There are many composting toilet options now (even with a flush – water – system). At my own house we designed and had made up (polypropelene) a dry composting toilet based on the BioLoo system. Our toilet is located at the end of the laundry, accessed by the back porch (not inside the house – earthy smell, occasionally whiffy if too much moisture). The worms thrive in it (its not a hot compost).

    That still leaves the grey water to deal with. Grey water that doesn’t involve cooking water, sink, etc, is much easier to deal with. (Kitchen sink water is full of fats, solids, etc) Now it depends on whether you want an off the shelf option or design and build as you go.

    A grey water system I know well uses gravity to direct water into a gravel filled old bath (first filter) then drains into a wet area of bush. This drained water could just as easily be directed to more useful places. (The water from the kitchen sink first goes through a grease trap). This system depends on A). Gravity (slope), and; B). Land area (enough to have a wet area/evaporation zone).

    If you want to go down the simple system route its probably best to ask around and try to get a hold of plans that have been approved for something you like (if seeking formal permission – you should always make sure it works well whether approved to regulation or not though).

    I hope that helps a little.

    Eion Scott

    Hi Panapa, council consenting is different depending on local soils, density of housing etc, most have a requirement to connect to a wastewater system if it is available, but there’s nothing stopping you using an onsite wastewater system if you choose. You will have to meet stormwater and wasstewater discharge regs, and if reusing greywater for irrigation or toilet flushing, hygiene standards. If your soils are free draining, your council may allow you to use greywater for irrigation, but Auckland has a standard (TP58) which means you will need Resource Consent, and the cost of doing so means nobody has ever applied, as far as I know. Here’s some detail:

    We recommend reusing greywater in toilets only, and this requires a building consent. You will need to satisfy the consents processing staff that your system is hygienic. Usually that means some form of treatment (chlorine tablets in the greywater tanks or similar). The main objective is to not hold greywater in a tank for long periods. There should also be a mains auxilliary supply to the toilet to provide amenity if the tank is dry.

    Level is the BRANZ website, primarily for designers, so has good technical detail. Go to http://www.level.org.nz/water/wastewater/on-site-wastewater-treatment/greywater-recycling/.

    The following greywater reuse systems may be available in Auckland (but will need to comply with Auckland Council requirements above to be installed in the metropolitan area):

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